[{"Name":"Sensory Processes","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Sensations and Receptors","Duration":"6m 56s","ChapterTopicVideoID":28509,"CourseChapterTopicPlaylistID":284104,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.990","Text":"I\u0027m very glad that you\u0027re back to discuss the continuation of the nervous system."},{"Start":"00:06.990 ","End":"00:11.250","Text":"Now we\u0027re going to be talking about sensory processes."},{"Start":"00:11.250 ","End":"00:17.880","Text":"That is, how the cell or how the body senses what\u0027s going on around it,"},{"Start":"00:17.880 ","End":"00:22.815","Text":"and then translates that into either a thought or action."},{"Start":"00:22.815 ","End":"00:26.610","Text":"Of course, sensory receptor cells are"},{"Start":"00:26.610 ","End":"00:30.900","Text":"found in various places in the body and on the body."},{"Start":"00:30.900 ","End":"00:33.300","Text":"There are these neural pathways that are going to"},{"Start":"00:33.300 ","End":"00:37.050","Text":"transmit the signals and there are various parts of the brain,"},{"Start":"00:37.050 ","End":"00:40.290","Text":"of course, which are involved in the sensory perception."},{"Start":"00:40.290 ","End":"00:43.235","Text":"We discussed a little of that earlier."},{"Start":"00:43.235 ","End":"00:47.840","Text":"Interestingly, the senses are able to convert"},{"Start":"00:47.840 ","End":"00:52.880","Text":"a stimulus from the outside into an electrical signal in the nervous system."},{"Start":"00:52.880 ","End":"00:55.880","Text":"All bilaterally symmetric animals,"},{"Start":"00:55.880 ","End":"01:00.560","Text":"that\u0027s most animals that have 2 sides that are symmetric, 1 to the other,"},{"Start":"01:00.560 ","End":"01:05.300","Text":"it seems that all of them have this sensory system,"},{"Start":"01:05.300 ","End":"01:10.730","Text":"but they differ amongst species according to the demands of their environments."},{"Start":"01:10.730 ","End":"01:13.310","Text":"For instance, in this picture,"},{"Start":"01:13.310 ","End":"01:16.085","Text":"you can see there\u0027s an owl, he has very,"},{"Start":"01:16.085 ","End":"01:21.380","Text":"very highly developed eyes in order to sense what he sees"},{"Start":"01:21.380 ","End":"01:27.725","Text":"because he will see his prey and then he\u0027ll go and try to get it."},{"Start":"01:27.725 ","End":"01:30.380","Text":"Whereas the pig on the right has"},{"Start":"01:30.380 ","End":"01:35.270","Text":"a particularly highly developed nose because it\u0027s very important"},{"Start":"01:35.270 ","End":"01:43.280","Text":"for the pig to be able to distinguish what is food and what is not."},{"Start":"01:43.280 ","End":"01:47.750","Text":"They differ according to the demands of their environment,"},{"Start":"01:47.750 ","End":"01:50.360","Text":"but the idea is the same."},{"Start":"01:50.360 ","End":"01:55.745","Text":"Now, there are different types of sensation and different types of"},{"Start":"01:55.745 ","End":"02:02.005","Text":"organs which can sense these various external stimuli."},{"Start":"02:02.005 ","End":"02:03.720","Text":"For instance, there\u0027s olfaction,"},{"Start":"02:03.720 ","End":"02:05.270","Text":"that\u0027s smell through the nose."},{"Start":"02:05.270 ","End":"02:08.240","Text":"There\u0027s what\u0027s called gustation, that\u0027s tasting,"},{"Start":"02:08.240 ","End":"02:11.795","Text":"which would be in our tongue and on the roof of our mouths"},{"Start":"02:11.795 ","End":"02:16.130","Text":"there\u0027s equilibrium so we know whether we\u0027re standing still,"},{"Start":"02:16.130 ","End":"02:18.410","Text":"or we\u0027re moving, or we\u0027re balanced,"},{"Start":"02:18.410 ","End":"02:20.095","Text":"or we\u0027re not balanced."},{"Start":"02:20.095 ","End":"02:25.130","Text":"Those things occur to a degree at least in the inner ear."},{"Start":"02:25.130 ","End":"02:26.990","Text":"There\u0027s vision, of course, which is the eye."},{"Start":"02:26.990 ","End":"02:28.910","Text":"There\u0027s hearing, which is the ear."},{"Start":"02:28.910 ","End":"02:31.670","Text":"There\u0027s electroreception."},{"Start":"02:31.670 ","End":"02:33.769","Text":"There are some birds in particular,"},{"Start":"02:33.769 ","End":"02:38.510","Text":"they can tell the differences between electric fields in various places,"},{"Start":"02:38.510 ","End":"02:41.780","Text":"and some birds evidently also are able"},{"Start":"02:41.780 ","End":"02:44.960","Text":"to determine what the magnetic field is and we think"},{"Start":"02:44.960 ","End":"02:48.350","Text":"that it may be that they know how to"},{"Start":"02:48.350 ","End":"02:52.910","Text":"navigate when they migrate based on the magnetism of the Earth."},{"Start":"02:52.910 ","End":"02:59.615","Text":"In any case, there are these various organs which receive various external signals."},{"Start":"02:59.615 ","End":"03:06.425","Text":"Now, these signals then can be classified in various ways,"},{"Start":"03:06.425 ","End":"03:10.415","Text":"and the receptors can be classified in various ways."},{"Start":"03:10.415 ","End":"03:14.780","Text":"Let\u0027s start out by discussing somatosensation."},{"Start":"03:14.780 ","End":"03:18.050","Text":"That\u0027s sensation that is received by the skin,"},{"Start":"03:18.050 ","End":"03:20.030","Text":"the mucous membranes, the limbs and the joints."},{"Start":"03:20.030 ","End":"03:23.580","Text":"In other words, what we feel on the outside,"},{"Start":"03:23.580 ","End":"03:25.560","Text":"like pressure for instance."},{"Start":"03:25.560 ","End":"03:31.015","Text":"It might be even pain that we feel on our skin, limbs and joints."},{"Start":"03:31.015 ","End":"03:37.160","Text":"It occurs all over our body and in some particular locations inside the body,"},{"Start":"03:37.160 ","End":"03:39.230","Text":"it\u0027s not everywhere inside the body."},{"Start":"03:39.230 ","End":"03:41.855","Text":"Sometimes you can get, for instance,"},{"Start":"03:41.855 ","End":"03:44.900","Text":"you can get cut in various parts inside"},{"Start":"03:44.900 ","End":"03:48.380","Text":"the body and you don\u0027t feel them because there are no receptors there."},{"Start":"03:48.380 ","End":"03:51.619","Text":"Another kind of sensation is vestibular sensation."},{"Start":"03:51.619 ","End":"03:54.810","Text":"That\u0027s this spatial orientation and balance."},{"Start":"03:54.810 ","End":"03:56.210","Text":"You can see, for instance,"},{"Start":"03:56.210 ","End":"04:00.950","Text":"that this woman over here is standing on her hands,"},{"Start":"04:00.950 ","End":"04:06.370","Text":"but her body is not quite the way a normal person stands up."},{"Start":"04:06.370 ","End":"04:10.900","Text":"But her balance and whatnot is regulated"},{"Start":"04:10.900 ","End":"04:16.015","Text":"by these vestibular organs which are in the back of the brain,"},{"Start":"04:16.015 ","End":"04:21.650","Text":"and they help her with her spot through spatial orientation and her balance."},{"Start":"04:22.190 ","End":"04:27.115","Text":"Next actually is proprioception."},{"Start":"04:27.115 ","End":"04:34.990","Text":"That is really distinguished or it\u0027s explained best in this picture here."},{"Start":"04:34.990 ","End":"04:38.080","Text":"It\u0027s the various positions of the bones, joints, and muscles,"},{"Start":"04:38.080 ","End":"04:43.540","Text":"our brain is able to integrate all these things and that\u0027s called"},{"Start":"04:43.540 ","End":"04:47.770","Text":"proprioception that integrates the various stimuli"},{"Start":"04:47.770 ","End":"04:51.980","Text":"that lets us understand if we\u0027re upside down or not upside down and so on."},{"Start":"04:51.980 ","End":"04:55.610","Text":"Finally, there\u0027s the issue of movement."},{"Start":"04:55.610 ","End":"04:57.545","Text":"Kine means movement,"},{"Start":"04:57.545 ","End":"05:02.000","Text":"so kinesthesia is limb movement and tracking."},{"Start":"05:02.000 ","End":"05:04.730","Text":"Of course we can tell whether we\u0027re moving,"},{"Start":"05:04.730 ","End":"05:06.785","Text":"whether our limbs are moving,"},{"Start":"05:06.785 ","End":"05:12.875","Text":"and there are these different sensation from something just touching us."},{"Start":"05:12.875 ","End":"05:20.835","Text":"Now let\u0027s get an overview of how the senses then are interpreted by the body."},{"Start":"05:20.835 ","End":"05:26.914","Text":"In this example, let\u0027s say we have a brown bear which is foraging along a river bank,"},{"Start":"05:26.914 ","End":"05:28.730","Text":"there are 2 possibilities."},{"Start":"05:28.730 ","End":"05:29.840","Text":"It\u0027s foraging for food,"},{"Start":"05:29.840 ","End":"05:33.530","Text":"either there\u0027s food which is present or it absence."},{"Start":"05:33.530 ","End":"05:38.585","Text":"Of course it\u0027s going to behave differently whether or not it finds food."},{"Start":"05:38.585 ","End":"05:46.070","Text":"There is a sensory input which then gets transduced."},{"Start":"05:46.070 ","End":"05:48.860","Text":"It gets converted to some sort of a stimulus and"},{"Start":"05:48.860 ","End":"05:52.940","Text":"electrical signal that goes to the brain of the bear,"},{"Start":"05:52.940 ","End":"05:56.165","Text":"so that it\u0027s going to know how to behave,"},{"Start":"05:56.165 ","End":"05:59.570","Text":"and there is a receptor potential."},{"Start":"05:59.570 ","End":"06:02.870","Text":"In other words, there is a sensory receptor"},{"Start":"06:02.870 ","End":"06:07.100","Text":"converts a stimulus into a change in the membrane potential."},{"Start":"06:07.100 ","End":"06:09.740","Text":"We know that by understanding or we can expect"},{"Start":"06:09.740 ","End":"06:12.845","Text":"this because we understand how nerves work."},{"Start":"06:12.845 ","End":"06:18.380","Text":"There is a membrane potential which changes as a result of"},{"Start":"06:18.380 ","End":"06:22.242","Text":"a stimulus to a particular receptor"},{"Start":"06:22.242 ","End":"06:26.135","Text":"so that when a stimulus is received and processed by the nervous system,"},{"Start":"06:26.135 ","End":"06:31.310","Text":"there is a possibility for a motor response either to try to bite,"},{"Start":"06:31.310 ","End":"06:33.215","Text":"say to eat some food,"},{"Start":"06:33.215 ","End":"06:34.805","Text":"or if there was no food,"},{"Start":"06:34.805 ","End":"06:36.565","Text":"not to do that."},{"Start":"06:36.565 ","End":"06:40.880","Text":"This could either involve a simple reflex or it could be"},{"Start":"06:40.880 ","End":"06:47.540","Text":"more substantial processing which requires really the brain of the animal to work."},{"Start":"06:47.540 ","End":"06:52.235","Text":"Let\u0027s look at these sensors now more specifically,"},{"Start":"06:52.235 ","End":"06:56.640","Text":"and we\u0027ll do that in the next video."}],"ID":29998},{"Watched":false,"Name":"Receptors Transduce and Transmit Signals","Duration":"3m 29s","ChapterTopicVideoID":28508,"CourseChapterTopicPlaylistID":284104,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.519","Text":"Let\u0027s continue our discussion of sensation and the sensory process."},{"Start":"00:05.519 ","End":"00:09.810","Text":"We discussed the fact that there are receptors."},{"Start":"00:09.810 ","End":"00:14.070","Text":"Let\u0027s now look at a specialized receptor, for instance,"},{"Start":"00:14.070 ","End":"00:16.575","Text":"that might be in a cell."},{"Start":"00:16.575 ","End":"00:19.245","Text":"Hair, cells."},{"Start":"00:19.245 ","End":"00:24.030","Text":"Their hair\u0027s out there and when those hairs move,"},{"Start":"00:24.030 ","End":"00:27.300","Text":"because they sense something on the outside,"},{"Start":"00:27.300 ","End":"00:29.550","Text":"let\u0027s say whiskers, for instance,"},{"Start":"00:29.550 ","End":"00:39.690","Text":"they might set up a stimulus now which results in change in potential in the synapse,"},{"Start":"00:39.690 ","End":"00:46.140","Text":"and the nerve to which this specialized receptor is attached."},{"Start":"00:46.140 ","End":"00:50.120","Text":"A cell or cell process that is specialized to engage"},{"Start":"00:50.120 ","End":"00:53.905","Text":"with and detect stimulus is called a receptor."},{"Start":"00:53.905 ","End":"01:00.845","Text":"The stimulation of this receptor then sends a signal to the central nervous system."},{"Start":"01:00.845 ","End":"01:05.270","Text":"Some of the nerves, however,"},{"Start":"01:05.270 ","End":"01:08.675","Text":"do not have a specialized receptor at the end,"},{"Start":"01:08.675 ","End":"01:11.300","Text":"they have free nerve endings."},{"Start":"01:11.300 ","End":"01:17.060","Text":"For instance, say the nerves that are in our gums can feel pain,"},{"Start":"01:17.060 ","End":"01:18.500","Text":"they can feel hot and cold,"},{"Start":"01:18.500 ","End":"01:23.690","Text":"they can feel all sorts of things directly without having specific receptors there."},{"Start":"01:23.690 ","End":"01:29.930","Text":"They\u0027re simply sensitive to these various changes and those respond to"},{"Start":"01:29.930 ","End":"01:37.070","Text":"stimuli in the external environment in a rather non-specific way."},{"Start":"01:37.070 ","End":"01:40.550","Text":"They can be stimulated, as I said,"},{"Start":"01:40.550 ","End":"01:45.050","Text":"by several different stimuli and not specific ones."},{"Start":"01:45.050 ","End":"01:49.355","Text":"Now, what happens once there\u0027s a stimulus,"},{"Start":"01:49.355 ","End":"01:52.798","Text":"which is usually energy of some sort."},{"Start":"01:52.798 ","End":"01:54.500","Text":"It could be, let\u0027s say, light energy if"},{"Start":"01:54.500 ","End":"01:58.960","Text":"it\u0027s going to be affecting the receptors in your eye,"},{"Start":"01:58.960 ","End":"02:01.700","Text":"but it could be touch,"},{"Start":"02:01.700 ","End":"02:06.179","Text":"it could be temperature, it could be various kinds of energies."},{"Start":"02:06.179 ","End":"02:09.145","Text":"In this case let\u0027s say,"},{"Start":"02:09.145 ","End":"02:14.360","Text":"will enter the eye and there will be a receptor"},{"Start":"02:14.360 ","End":"02:20.075","Text":"that detects the light in a process called reception."},{"Start":"02:20.075 ","End":"02:27.065","Text":"Then that receptor or the reception there is then transduced."},{"Start":"02:27.065 ","End":"02:35.510","Text":"It is converted from light energy to an action potential which is in the nerves."},{"Start":"02:35.510 ","End":"02:42.005","Text":"That change in the energy is called transduction."},{"Start":"02:42.005 ","End":"02:47.880","Text":"Next, of course, that nerve is going to transmit"},{"Start":"02:47.880 ","End":"02:54.815","Text":"the signal down its axon to possibly the brain, for instance."},{"Start":"02:54.815 ","End":"02:59.330","Text":"Let\u0027s say in this case it would be in the brain via the optic nerve,"},{"Start":"02:59.330 ","End":"03:03.095","Text":"and so that we would then perceive it,"},{"Start":"03:03.095 ","End":"03:06.420","Text":"there would be perception in the brain."},{"Start":"03:06.420 ","End":"03:14.135","Text":"This overall pathway then starts out with a stimulus which is received by receptors,"},{"Start":"03:14.135 ","End":"03:17.840","Text":"is transduced into a nervous signal,"},{"Start":"03:17.840 ","End":"03:23.705","Text":"is then transmitted from where the receptor is to the brain,"},{"Start":"03:23.705 ","End":"03:29.880","Text":"where it is then perceived in a process called perception."}],"ID":29999},{"Watched":false,"Name":"Sensory Reception","Duration":"7m 15s","ChapterTopicVideoID":28510,"CourseChapterTopicPlaylistID":284104,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.770","Text":"Welcome back to our discussion of sensory reception."},{"Start":"00:04.770 ","End":"00:08.190","Text":"In other words, what happens when we sense things from the outside?"},{"Start":"00:08.190 ","End":"00:12.645","Text":"Of course, there is the reception of some signal,"},{"Start":"00:12.645 ","End":"00:15.630","Text":"which could be something that we see,"},{"Start":"00:15.630 ","End":"00:17.625","Text":"we smell, we taste, hear, touch."},{"Start":"00:17.625 ","End":"00:20.385","Text":"Of course, these are the 5 senses."},{"Start":"00:20.385 ","End":"00:25.560","Text":"Yes. There are various signals from the outside that we can sense,"},{"Start":"00:25.560 ","End":"00:31.155","Text":"and then something happens in response to those senses."},{"Start":"00:31.155 ","End":"00:33.570","Text":"The first thing that has to happen, of course,"},{"Start":"00:33.570 ","End":"00:35.970","Text":"is we have to receive the signal."},{"Start":"00:35.970 ","End":"00:38.900","Text":"If a light turns on, for instance,"},{"Start":"00:38.900 ","End":"00:44.165","Text":"our eye is going to see that signal."},{"Start":"00:44.165 ","End":"00:47.630","Text":"A signal is detected and then, what happens?"},{"Start":"00:47.630 ","End":"00:48.785","Text":"How does that happen?"},{"Start":"00:48.785 ","End":"00:51.199","Text":"Well, in the case of the eye, for instance,"},{"Start":"00:51.199 ","End":"00:56.285","Text":"there is a molecule that changes its confirmation"},{"Start":"00:56.285 ","End":"01:01.310","Text":"and then leads to a cascade of chemical events in the receptor,"},{"Start":"01:01.310 ","End":"01:04.265","Text":"which at the end of the day, what do they do?"},{"Start":"01:04.265 ","End":"01:10.955","Text":"They cause an action potential in the nerves"},{"Start":"01:10.955 ","End":"01:17.915","Text":"that are attached to the receptor and that happens in a process called transduction."},{"Start":"01:17.915 ","End":"01:19.550","Text":"Now, during this transduction,"},{"Start":"01:19.550 ","End":"01:24.833","Text":"that is the movement of the signal from the receptor down the nerve,"},{"Start":"01:24.833 ","End":"01:27.560","Text":"there is also amplification."},{"Start":"01:27.560 ","End":"01:33.290","Text":"That means that they could have a very small signal that results in"},{"Start":"01:33.290 ","End":"01:41.435","Text":"a large currents or a large response in,"},{"Start":"01:41.435 ","End":"01:43.370","Text":"let\u0027s say, many nerves,"},{"Start":"01:43.370 ","End":"01:46.510","Text":"it depends on the case."},{"Start":"01:46.510 ","End":"01:49.940","Text":"There, in addition to increasing the signal,"},{"Start":"01:49.940 ","End":"01:53.450","Text":"there is also something called sensory adaptation."},{"Start":"01:53.450 ","End":"01:55.865","Text":"That could be that there\u0027s a decrease,"},{"Start":"01:55.865 ","End":"02:01.785","Text":"actually a decrease in the responsiveness to continued stimulation."},{"Start":"02:01.785 ","End":"02:04.100","Text":"Let\u0027s look at this, for instance,"},{"Start":"02:04.100 ","End":"02:06.740","Text":"something that you are actually quite familiar with."},{"Start":"02:06.740 ","End":"02:11.794","Text":"If they decrease their ability to respond these receptors,"},{"Start":"02:11.794 ","End":"02:15.260","Text":"you may get something like the following."},{"Start":"02:15.260 ","End":"02:20.810","Text":"You first taste something and you\u0027ll get a big taste sensation."},{"Start":"02:20.810 ","End":"02:24.020","Text":"Let\u0027s say you\u0027ve tasted a glass of wine that was particularly good."},{"Start":"02:24.020 ","End":"02:26.240","Text":"But then as you keep tasting it,"},{"Start":"02:26.240 ","End":"02:32.450","Text":"the response that you get goes down with time or with a number of different tastes."},{"Start":"02:32.450 ","End":"02:35.705","Text":"That would be called sensory adaptation"},{"Start":"02:35.705 ","End":"02:39.595","Text":"or a decrease in responsiveness to continued stimulation."},{"Start":"02:39.595 ","End":"02:41.600","Text":"Now, why would this be useful?"},{"Start":"02:41.600 ","End":"02:43.820","Text":"It might be useful, for instance,"},{"Start":"02:43.820 ","End":"02:48.320","Text":"to help free up resources for other stimuli that are going on."},{"Start":"02:48.320 ","End":"02:52.115","Text":"Let\u0027s say you\u0027re tasting some wine and at the same time,"},{"Start":"02:52.115 ","End":"02:53.495","Text":"there is some light flashing."},{"Start":"02:53.495 ","End":"02:57.470","Text":"It might be important for you to see that light flashing or somebody"},{"Start":"02:57.470 ","End":"02:59.390","Text":"walking in front of you or somebody"},{"Start":"02:59.390 ","End":"03:02.435","Text":"punching you in the face even though you\u0027re tasting the wine."},{"Start":"03:02.435 ","End":"03:07.460","Text":"1 way that the body helps transfer the responsiveness from"},{"Start":"03:07.460 ","End":"03:13.595","Text":"1 sense to another is by this sensory adaptation."},{"Start":"03:13.595 ","End":"03:17.060","Text":"Now there are 2 different receptors."},{"Start":"03:17.060 ","End":"03:22.955","Text":"There are what are called tonic receptors and there are phasic receptors."},{"Start":"03:22.955 ","End":"03:32.045","Text":"The tonic receptors are going to be those that maintain some continual stimulus."},{"Start":"03:32.045 ","End":"03:33.530","Text":"They could tell you to fire to"},{"Start":"03:33.530 ","End":"03:38.135","Text":"relatively constant rates as long as the stimulus is maintained."},{"Start":"03:38.135 ","End":"03:39.380","Text":"For instance, for pressure,"},{"Start":"03:39.380 ","End":"03:43.520","Text":"as long as you feel pressure on a particular point in your body,"},{"Start":"03:43.520 ","End":"03:47.405","Text":"you\u0027re going to feel that stimulus that\u0027s not go away."},{"Start":"03:47.405 ","End":"03:53.240","Text":"On the other hand, there are these phasic receptors which are slow adapting."},{"Start":"03:53.240 ","End":"03:56.360","Text":"You may initially feel something,"},{"Start":"03:56.360 ","End":"04:03.320","Text":"so you\u0027ll get a lot of firing of some neurons and then with time it subsides."},{"Start":"04:03.320 ","End":"04:07.400","Text":"That\u0027s similar to what we showed you with the wine a minute ago and there"},{"Start":"04:07.400 ","End":"04:12.300","Text":"are these nociceptors and proprioceptors."},{"Start":"04:12.300 ","End":"04:14.105","Text":"The nociceptors, for instance,"},{"Start":"04:14.105 ","End":"04:16.145","Text":"are those which cause pain."},{"Start":"04:16.145 ","End":"04:19.220","Text":"You know that you initially may have a lot of pain,"},{"Start":"04:19.220 ","End":"04:20.450","Text":"let\u0027s say after a bee sting,"},{"Start":"04:20.450 ","End":"04:26.105","Text":"but then it subsides somewhat with time and the same thing with these receptors,"},{"Start":"04:26.105 ","End":"04:31.264","Text":"the proprioceptors that are involved in where in space"},{"Start":"04:31.264 ","End":"04:37.580","Text":"your body is so that you get used to that and you know what\u0027s going on."},{"Start":"04:37.580 ","End":"04:40.520","Text":"Now, when you receive a signal,"},{"Start":"04:40.520 ","End":"04:43.977","Text":"we menti1d that there can be sensory amplification."},{"Start":"04:43.977 ","End":"04:45.455","Text":"Now, how might that work?"},{"Start":"04:45.455 ","End":"04:46.970","Text":"In this case, for instance,"},{"Start":"04:46.970 ","End":"04:51.320","Text":"you can have 1 signal molecule from the outside,"},{"Start":"04:51.320 ","End":"04:54.919","Text":"which then interacts with 1 particular receptor."},{"Start":"04:54.919 ","End":"04:59.030","Text":"That receptor then might be associated with"},{"Start":"04:59.030 ","End":"05:03.380","Text":"another protein called a G-protein and then there\u0027s a cascade of events,"},{"Start":"05:03.380 ","End":"05:05.675","Text":"something called signal transduction,"},{"Start":"05:05.675 ","End":"05:07.280","Text":"in which as you can see,"},{"Start":"05:07.280 ","End":"05:10.510","Text":"multiple molecules become involved."},{"Start":"05:10.510 ","End":"05:14.810","Text":"The cell response involves many molecules,"},{"Start":"05:14.810 ","End":"05:21.180","Text":"whereas the initial 1 or the initial signal came from only 1 molecule."},{"Start":"05:21.180 ","End":"05:23.495","Text":"This is an example of signal transduction,"},{"Start":"05:23.495 ","End":"05:27.845","Text":"which does sensory amplification."},{"Start":"05:27.845 ","End":"05:29.780","Text":"In addition to all this,"},{"Start":"05:29.780 ","End":"05:33.530","Text":"where you feel something may be determined"},{"Start":"05:33.530 ","End":"05:37.820","Text":"by how many nerves you have in a particular area."},{"Start":"05:37.820 ","End":"05:45.185","Text":"Let\u0027s say you have 1 neuron and its dendrites stretch over a long piece of skin."},{"Start":"05:45.185 ","End":"05:50.315","Text":"If you are poked in 1 place and then poked someplace nearby,"},{"Start":"05:50.315 ","End":"05:54.725","Text":"that may feel the same to you because it\u0027s only 1 neuron which is responding."},{"Start":"05:54.725 ","End":"05:58.795","Text":"Let\u0027s say if you get poked on your shoulder or in your back,"},{"Start":"05:58.795 ","End":"06:01.835","Text":"and that\u0027s less precise detection."},{"Start":"06:01.835 ","End":"06:05.330","Text":"On the other hand, if you are poked in your hand,"},{"Start":"06:05.330 ","End":"06:11.450","Text":"so in your hand you have lots of neurons and then you\u0027ll be able to distinguish where"},{"Start":"06:11.450 ","End":"06:18.315","Text":"exactly you got poked and that can result in more precise detection."},{"Start":"06:18.315 ","End":"06:20.045","Text":"As we have said,"},{"Start":"06:20.045 ","End":"06:22.385","Text":"there are different senses."},{"Start":"06:22.385 ","End":"06:23.900","Text":"For instance, there\u0027s touch,"},{"Start":"06:23.900 ","End":"06:26.195","Text":"there\u0027s hearing, there\u0027s vision among others."},{"Start":"06:26.195 ","End":"06:28.670","Text":"They work at different distances."},{"Start":"06:28.670 ","End":"06:31.190","Text":"When you touch something, of course,"},{"Start":"06:31.190 ","End":"06:34.250","Text":"the stimulus must come into contact with the body and therefore,"},{"Start":"06:34.250 ","End":"06:40.555","Text":"you\u0027re going to have a particular receptor that\u0027s going to be sensitive to touch."},{"Start":"06:40.555 ","End":"06:46.550","Text":"With hearing, the stimulus can be further away and there this sensation or"},{"Start":"06:46.550 ","End":"06:53.405","Text":"the sensors are going to be those that are moved by airwaves,"},{"Start":"06:53.405 ","End":"06:55.750","Text":"by sound waves that are in your ear."},{"Start":"06:55.750 ","End":"06:58.865","Text":"Of course, they\u0027re the stimulus can be further with vision,"},{"Start":"06:58.865 ","End":"07:00.830","Text":"you can have a stimulus just really far away."},{"Start":"07:00.830 ","End":"07:01.985","Text":"It could be a star,"},{"Start":"07:01.985 ","End":"07:06.755","Text":"even which is emitting photons and you\u0027d need special receptors,"},{"Start":"07:06.755 ","End":"07:10.655","Text":"the receptors that are in your eyes in order to see those."},{"Start":"07:10.655 ","End":"07:15.750","Text":"Of course, they\u0027re processed also in different parts of the brain."}],"ID":30000},{"Watched":false,"Name":"Transduction","Duration":"6m 44s","ChapterTopicVideoID":28511,"CourseChapterTopicPlaylistID":284104,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.322","Text":"We\u0027re back now to discussing more details of sensory transduction"},{"Start":"00:05.322 ","End":"00:10.230","Text":"and I\u0027m glad you\u0027ve come back to learn about this more in depth."},{"Start":"00:10.230 ","End":"00:16.035","Text":"We\u0027re now going to look at what happens in a greater detail at various receptors."},{"Start":"00:16.035 ","End":"00:19.440","Text":"Of course, there\u0027s the conversion of the stimulus that we discussed"},{"Start":"00:19.440 ","End":"00:24.285","Text":"earlier into an electrical signal in the nervous system."},{"Start":"00:24.285 ","End":"00:31.050","Text":"This takes place at a sensory receptor, as we discussed."},{"Start":"00:31.050 ","End":"00:36.030","Text":"Let\u0027s look now what happens in greater detail as I just said."},{"Start":"00:36.030 ","End":"00:43.670","Text":"There is a potential which occurs in the nerve cells that are attached to a receptor."},{"Start":"00:43.670 ","End":"00:47.530","Text":"Here we could see a receptor that\u0027s in the ear,"},{"Start":"00:47.530 ","End":"00:50.810","Text":"and you can see that there are hairs which are going either"},{"Start":"00:50.810 ","End":"00:54.455","Text":"in one direction as the sound waves come from one direction,"},{"Start":"00:54.455 ","End":"00:57.725","Text":"or they can go in the other direction."},{"Start":"00:57.725 ","End":"01:02.390","Text":"There\u0027s a synapse between the receptor and"},{"Start":"01:02.390 ","End":"01:09.380","Text":"the nerve that is going to be transmitting the signal through transduction."},{"Start":"01:09.380 ","End":"01:12.880","Text":"Here you can see the action potentials which occur,"},{"Start":"01:12.880 ","End":"01:18.560","Text":"and what\u0027s interesting is there can be either depolarization or there can be"},{"Start":"01:18.560 ","End":"01:26.425","Text":"hyperpolarization depending on the direction that the hairs are moving."},{"Start":"01:26.425 ","End":"01:29.900","Text":"What\u0027s happening here is that the sensory receptor,"},{"Start":"01:29.900 ","End":"01:32.390","Text":"that\u0027s this sound receptor is converting"},{"Start":"01:32.390 ","End":"01:36.925","Text":"the stimulus energy into a change of its membrane potential,"},{"Start":"01:36.925 ","End":"01:42.290","Text":"and that that then is going to change the amount of neurotransmitter,"},{"Start":"01:42.290 ","End":"01:49.020","Text":"either a lot of it to cause depolarization or less of it to cause hyperpolarization,"},{"Start":"01:49.020 ","End":"01:53.240","Text":"and that will be a signal which will then be transmitted further, and of course,"},{"Start":"01:53.240 ","End":"02:00.955","Text":"that happens by opening ion gated channels as we learned earlier in the nerve cell."},{"Start":"02:00.955 ","End":"02:03.515","Text":"This is just, again,"},{"Start":"02:03.515 ","End":"02:07.340","Text":"confirmation of what I said before about there can be"},{"Start":"02:07.340 ","End":"02:13.265","Text":"either depolarization or hyperpolarization depending on the signal."},{"Start":"02:13.265 ","End":"02:14.870","Text":"Now in addition to that,"},{"Start":"02:14.870 ","End":"02:17.375","Text":"there can be graded potentials."},{"Start":"02:17.375 ","End":"02:22.100","Text":"In other words, the potential could be not either just on or off,"},{"Start":"02:22.100 ","End":"02:26.420","Text":"or it can have an amount associated with it,"},{"Start":"02:26.420 ","End":"02:30.440","Text":"an amplitude, a strength of the potential,"},{"Start":"02:30.440 ","End":"02:32.250","Text":"and that will be called a graded potential,"},{"Start":"02:32.250 ","End":"02:34.130","Text":"so if you have a stimulus point,"},{"Start":"02:34.130 ","End":"02:36.335","Text":"let\u0027s say someplace on your skin,"},{"Start":"02:36.335 ","End":"02:41.270","Text":"then you may feel it more in the center, in other words,"},{"Start":"02:41.270 ","End":"02:44.000","Text":"more at the point that the pressure is applied,"},{"Start":"02:44.000 ","End":"02:47.435","Text":"than further away in both directions."},{"Start":"02:47.435 ","End":"02:48.920","Text":"How might that work?"},{"Start":"02:48.920 ","End":"02:54.695","Text":"Well, the magnitude of the potential could depend on the strength of the stimulus."},{"Start":"02:54.695 ","End":"02:57.350","Text":"Very close to where the stimulus is,"},{"Start":"02:57.350 ","End":"03:05.975","Text":"you\u0027ll get a very large potential and further away you\u0027ll get a much smaller potential."},{"Start":"03:05.975 ","End":"03:08.240","Text":"This is unlike action potentials,"},{"Start":"03:08.240 ","End":"03:11.600","Text":"graded potentials lose their strength as they move through"},{"Start":"03:11.600 ","End":"03:15.995","Text":"the cell because there is leakage of charge across the membrane,"},{"Start":"03:15.995 ","End":"03:23.055","Text":"so it\u0027s a little bit less well insulated than an action potential requires."},{"Start":"03:23.055 ","End":"03:26.265","Text":"Let\u0027s look at the receptors."},{"Start":"03:26.265 ","End":"03:31.505","Text":"Here are the 5 different senses, vision, touch,"},{"Start":"03:31.505 ","End":"03:33.320","Text":"smell, hearing, and taste,"},{"Start":"03:33.320 ","End":"03:35.165","Text":"and for each of them,"},{"Start":"03:35.165 ","End":"03:37.055","Text":"there are different receptors."},{"Start":"03:37.055 ","End":"03:44.070","Text":"For instance, in vision there will be rods and cones that are receptor,"},{"Start":"03:44.070 ","End":"03:45.180","Text":"touch, smell, hearing,"},{"Start":"03:45.180 ","End":"03:47.680","Text":"they each have different receptors."},{"Start":"03:47.680 ","End":"03:54.760","Text":"Here\u0027s the hearing with the little hairs as we discussed in the previous slide."},{"Start":"03:54.760 ","End":"04:00.215","Text":"Of course, each of these is activated by a different stimulus,"},{"Start":"04:00.215 ","End":"04:03.590","Text":"but the brain can integrate some of"},{"Start":"04:03.590 ","End":"04:09.220","Text":"these stimuli and make a new signal out of a combination of different signals."},{"Start":"04:09.220 ","End":"04:13.820","Text":"For instance, smell and taste can work"},{"Start":"04:13.820 ","End":"04:20.120","Text":"together to give us a better sense of what it is that we\u0027re eating."},{"Start":"04:20.120 ","End":"04:25.880","Text":"Once the nerve is activated by some stimulus, yes,"},{"Start":"04:25.880 ","End":"04:28.833","Text":"it\u0027s through a sensory organ,"},{"Start":"04:28.833 ","End":"04:33.665","Text":"we could say that there are 4 aspects of sensory information encoded."},{"Start":"04:33.665 ","End":"04:35.450","Text":"There is the type of stimulus,"},{"Start":"04:35.450 ","End":"04:38.173","Text":"the location of the stimulus,"},{"Start":"04:38.173 ","End":"04:40.100","Text":"there is the duration,"},{"Start":"04:40.100 ","End":"04:42.185","Text":"how long the stimulus lasts,"},{"Start":"04:42.185 ","End":"04:44.769","Text":"and there\u0027s the relative intensity."},{"Start":"04:44.769 ","End":"04:49.205","Text":"The type of stimulus could be, for instance, pain,"},{"Start":"04:49.205 ","End":"04:52.220","Text":"temperature, it could be vision,"},{"Start":"04:52.220 ","End":"04:55.595","Text":"in other words, it could be light and it could be sound, and so on."},{"Start":"04:55.595 ","End":"04:58.280","Text":"The location be where it is that we feel it,"},{"Start":"04:58.280 ","End":"05:01.145","Text":"that would certainly be the case in the case of touch."},{"Start":"05:01.145 ","End":"05:04.369","Text":"Duration, how long that stimulus lasts."},{"Start":"05:04.369 ","End":"05:06.800","Text":"Let\u0027s say the light is on for certain amount of time,"},{"Start":"05:06.800 ","End":"05:09.960","Text":"the pressure is applied for certain amount of time,"},{"Start":"05:09.960 ","End":"05:12.890","Text":"and how strong that stimulus is."},{"Start":"05:12.890 ","End":"05:14.765","Text":"Now how is that encoded?"},{"Start":"05:14.765 ","End":"05:22.840","Text":"While the intensity encoding is done using a difference in frequency coding,"},{"Start":"05:22.840 ","End":"05:27.415","Text":"that is the rate of the action potentials increased with increased intensity."},{"Start":"05:27.415 ","End":"05:29.440","Text":"With just gentle pressure,"},{"Start":"05:29.440 ","End":"05:37.150","Text":"the sensory receptor will fire at a certain frequency."},{"Start":"05:37.150 ","End":"05:39.805","Text":"However, if the pressure is increased,"},{"Start":"05:39.805 ","End":"05:43.495","Text":"the frequency of the action potentials will also"},{"Start":"05:43.495 ","End":"05:48.354","Text":"increase and then the brain will know that the pressure has increased."},{"Start":"05:48.354 ","End":"05:52.030","Text":"Now may be that the intensity encoding is not"},{"Start":"05:52.030 ","End":"05:56.200","Text":"only done by the frequency which the signal gets there,"},{"Start":"05:56.200 ","End":"05:59.020","Text":"but how many times the brain sees it,"},{"Start":"05:59.020 ","End":"06:01.855","Text":"either by having a weak stimulus,"},{"Start":"06:01.855 ","End":"06:05.735","Text":"which is interacting with only a few dendrites on"},{"Start":"06:05.735 ","End":"06:09.510","Text":"a particular nerve cell that\u0027s transmitting it and"},{"Start":"06:09.510 ","End":"06:13.925","Text":"a strong stimulus would then activate more dendrites,"},{"Start":"06:13.925 ","End":"06:18.245","Text":"and therefore the signal would be more, or potentially,"},{"Start":"06:18.245 ","End":"06:23.479","Text":"you could have numerous nerves that are attached to a particular receptor"},{"Start":"06:23.479 ","End":"06:29.195","Text":"and several nerves would get activated when the stimulus is strong,"},{"Start":"06:29.195 ","End":"06:35.267","Text":"whereas fewer nerves would be activated when the stimulus is weaker."},{"Start":"06:35.267 ","End":"06:38.630","Text":"We could have either a single sensory unit that\u0027s"},{"Start":"06:38.630 ","End":"06:44.459","Text":"stimulated or we could have multiple sensory units stimulated."}],"ID":30001},{"Watched":false,"Name":"Interpretation of Stimuli in the Brain","Duration":"5m 49s","ChapterTopicVideoID":28507,"CourseChapterTopicPlaylistID":284104,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.550","Text":"In this video, we\u0027re going to continue our discussion of sensory perception and"},{"Start":"00:05.550 ","End":"00:11.130","Text":"begin to think about what happens when the information gets to the brain."},{"Start":"00:11.130 ","End":"00:15.705","Text":"The stimuli reach the brain as action potentials, of course,"},{"Start":"00:15.705 ","End":"00:20.850","Text":"through the various nerves that connect the sensory regions,"},{"Start":"00:20.850 ","End":"00:24.300","Text":"let\u0027s say the eye or the taste in the mouth or pain"},{"Start":"00:24.300 ","End":"00:28.140","Text":"or touch or whatever it is that we\u0027ve gotten through,"},{"Start":"00:28.140 ","End":"00:35.180","Text":"the spinal cord along particular dedicated neural pathways."},{"Start":"00:35.180 ","End":"00:39.465","Text":"Action potentials then travel from the receptor along"},{"Start":"00:39.465 ","End":"00:45.295","Text":"first-order sensory neurons which are dedicated to a particular stimulus."},{"Start":"00:45.295 ","End":"00:47.225","Text":"Let\u0027s look at that."},{"Start":"00:47.225 ","End":"00:49.280","Text":"The first-order neurons, of course,"},{"Start":"00:49.280 ","End":"00:52.070","Text":"are those that are connected to the receptors."},{"Start":"00:52.070 ","End":"00:55.820","Text":"A stimulus has affected a receptor,"},{"Start":"00:55.820 ","End":"01:02.295","Text":"and then an action potential goes through the afferent neuron to the first-order neuron,"},{"Start":"01:02.295 ","End":"01:07.980","Text":"and that usually will be to the spinal cord if it\u0027s from, say, our hand."},{"Start":"01:07.980 ","End":"01:12.525","Text":"Then it goes to a second order neuron"},{"Start":"01:12.525 ","End":"01:19.735","Text":"that will then go up the spinal cord and into the brain-stem,"},{"Start":"01:19.735 ","End":"01:26.585","Text":"and there it will be directed to or will connect to the thalamus,"},{"Start":"01:26.585 ","End":"01:29.825","Text":"which is going to be a clearing house that will"},{"Start":"01:29.825 ","End":"01:33.835","Text":"basically decide where the signal will go next,"},{"Start":"01:33.835 ","End":"01:35.480","Text":"and from there it goes to"},{"Start":"01:35.480 ","End":"01:43.460","Text":"a third order neuron that will then connect to a different part of the cortex,"},{"Start":"01:43.460 ","End":"01:47.040","Text":"here\u0027s a specific area of the cortex,"},{"Start":"01:47.040 ","End":"01:51.680","Text":"that depends on what sense it was that was"},{"Start":"01:51.680 ","End":"01:56.785","Text":"delivering or what neuron it was that was delivering the signal."},{"Start":"01:56.785 ","End":"02:01.040","Text":"There are many different potential signals that can come into the brain."},{"Start":"02:01.040 ","End":"02:06.875","Text":"Some of them may come directly say from an olfactory bulb,"},{"Start":"02:06.875 ","End":"02:08.180","Text":"which would be in our nose,"},{"Start":"02:08.180 ","End":"02:10.385","Text":"so that doesn\u0027t go through the spinal cord."},{"Start":"02:10.385 ","End":"02:14.960","Text":"The same thing would be true with signals that come from the eye,"},{"Start":"02:14.960 ","End":"02:18.380","Text":"yes, they will go directly to the cerebellum."},{"Start":"02:18.380 ","End":"02:23.420","Text":"But in any case, sensory stimuli are then"},{"Start":"02:23.420 ","End":"02:30.630","Text":"interpreted by the brain based on the pathway through which the nerve arrives."},{"Start":"02:30.630 ","End":"02:33.635","Text":"All sensory signals, except those from"},{"Start":"02:33.635 ","End":"02:37.910","Text":"the smelling area of the olfactory system are routed to the thalamus,"},{"Start":"02:37.910 ","End":"02:42.800","Text":"as I mentioned before for clearing and then to the cortex."},{"Start":"02:42.800 ","End":"02:46.640","Text":"The olfactory pathway that\u0027s from the nose,"},{"Start":"02:46.640 ","End":"02:52.345","Text":"goes directly into what\u0027s called the olfactory cortex."},{"Start":"02:52.345 ","End":"02:56.330","Text":"In addition, there\u0027s the equilibrium pathways,"},{"Start":"02:56.330 ","End":"03:01.250","Text":"depending on how you\u0027re located in space that are going to affect"},{"Start":"03:01.250 ","End":"03:06.499","Text":"lots of different things and they go directly to the cerebellum."},{"Start":"03:06.499 ","End":"03:09.619","Text":"Now, how is this information interpreted?"},{"Start":"03:09.619 ","End":"03:14.195","Text":"We all know that in a particular case,"},{"Start":"03:14.195 ","End":"03:15.380","Text":"some people, let\u0027s say,"},{"Start":"03:15.380 ","End":"03:18.680","Text":"will be cold and other people will be warm"},{"Start":"03:18.680 ","End":"03:22.625","Text":"despite the fact that the external situation is really the same,"},{"Start":"03:22.625 ","End":"03:29.510","Text":"the interpretation of the signals between individuals can be quite different,"},{"Start":"03:29.510 ","End":"03:32.380","Text":"but at a basic level, they\u0027re similar."},{"Start":"03:32.380 ","End":"03:35.870","Text":"There are individual differences in sensitivity."},{"Start":"03:35.870 ","End":"03:39.230","Text":"Sensitivity, for instance, tolerances to pain,"},{"Start":"03:39.230 ","End":"03:41.315","Text":"and the temperature and so on."},{"Start":"03:41.315 ","End":"03:46.705","Text":"We all know that some people can\u0027t stand going to the dentist because the pain is"},{"Start":"03:46.705 ","End":"03:53.480","Text":"excruciating whereas other people can tolerate the same kinds of treatments."},{"Start":"03:53.480 ","End":"03:54.860","Text":"How does that work?"},{"Start":"03:54.860 ","End":"04:00.695","Text":"Well, of course we know that there are all these different receptors,"},{"Start":"04:00.695 ","End":"04:03.920","Text":"mechanoreceptors, chemoreceptors, electroreceptors,"},{"Start":"04:03.920 ","End":"04:06.980","Text":"thermoreceptors, non receptors that are involved in pain."},{"Start":"04:06.980 ","End":"04:13.320","Text":"They\u0027re all these different receptors which are sensitive to different stimuli,"},{"Start":"04:13.320 ","End":"04:19.580","Text":"say a light, or they could be directly simulated by other nerves,"},{"Start":"04:19.580 ","End":"04:22.730","Text":"let\u0027s say a nerve which is at the surface."},{"Start":"04:22.730 ","End":"04:26.195","Text":"There can be those that are sensitive to pressure."},{"Start":"04:26.195 ","End":"04:30.140","Text":"Each of them works a little bit differently and"},{"Start":"04:30.140 ","End":"04:34.610","Text":"they often have different associated proteins with them,"},{"Start":"04:34.610 ","End":"04:44.585","Text":"which we will modulate the signal and then start an action potential through the nerve."},{"Start":"04:44.585 ","End":"04:48.110","Text":"Let\u0027s look for a moment at mechanoreceptors,"},{"Start":"04:48.110 ","End":"04:52.625","Text":"those that are sensitive to pressure."},{"Start":"04:52.625 ","End":"04:56.480","Text":"In that case, we can divide it even further,"},{"Start":"04:56.480 ","End":"04:59.195","Text":"there\u0027s tactile what something feels like,"},{"Start":"04:59.195 ","End":"05:06.380","Text":"the proprioceptors in which direction things are coming from, and the baroreceptors,"},{"Start":"05:06.380 ","End":"05:10.040","Text":"that is how much pressure really there is and what"},{"Start":"05:10.040 ","End":"05:14.270","Text":"the direction is the things that are coming from and that will be particularly true,"},{"Start":"05:14.270 ","End":"05:16.210","Text":"for instance, in the ear,"},{"Start":"05:16.210 ","End":"05:20.220","Text":"so they will respond to physical deformation, so these receptors,"},{"Start":"05:20.220 ","End":"05:23.360","Text":"let\u0027s say that they\u0027re in the ear can either be moved to the right,"},{"Start":"05:23.360 ","End":"05:24.770","Text":"these hairs or to the left,"},{"Start":"05:24.770 ","End":"05:29.810","Text":"or they can stay where they are in each of them will yield different membrane potentials."},{"Start":"05:29.810 ","End":"05:31.760","Text":"We alluded to this earlier,"},{"Start":"05:31.760 ","End":"05:34.310","Text":"and typically their ion channels which are"},{"Start":"05:34.310 ","End":"05:37.550","Text":"linked to particular structures like we see here,"},{"Start":"05:37.550 ","End":"05:41.805","Text":"these hairs that are sometimes called cilia."},{"Start":"05:41.805 ","End":"05:49.140","Text":"We\u0027ll continue our discussion of the different kinds of receptors in the next video."}],"ID":30002},{"Watched":false,"Name":"Different Receptors Provide Different Stimuli","Duration":"6m 2s","ChapterTopicVideoID":28506,"CourseChapterTopicPlaylistID":284104,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.995","Text":"In this video, we\u0027ll continue our discussion of the sensory perception,"},{"Start":"00:04.995 ","End":"00:08.340","Text":"with more details about the different kinds of receptors."},{"Start":"00:08.340 ","End":"00:11.805","Text":"If you remember, we were talking about mechanoreceptors,"},{"Start":"00:11.805 ","End":"00:15.824","Text":"those that can sense pressure in the previous."},{"Start":"00:15.824 ","End":"00:20.910","Text":"There are free nerve endings that are those that senses and"},{"Start":"00:20.910 ","End":"00:25.680","Text":"they\u0027re found in the skin and of course they can detect pressure,"},{"Start":"00:25.680 ","End":"00:30.248","Text":"touch, stretching, tickling, various kinds of sensations,"},{"Start":"00:30.248 ","End":"00:32.220","Text":"hence will have free nerve endings,"},{"Start":"00:32.220 ","End":"00:34.020","Text":"the dendrites that are there."},{"Start":"00:34.020 ","End":"00:38.300","Text":"They will attach of course to the surface of"},{"Start":"00:38.300 ","End":"00:43.700","Text":"the skin and the other end will be in the spinal cord."},{"Start":"00:43.700 ","End":"00:46.820","Text":"Now sometimes, these nerve endings,"},{"Start":"00:46.820 ","End":"00:52.955","Text":"they can be encapsulated and that then will give a different kind of sensation."},{"Start":"00:52.955 ","End":"00:59.210","Text":"It will depend exactly on what kind of mechanoreceptor there is in"},{"Start":"00:59.210 ","End":"01:02.090","Text":"a particular part of the skin that will provide"},{"Start":"01:02.090 ","End":"01:05.315","Text":"specialized information about touch, pressure, vibration."},{"Start":"01:05.315 ","End":"01:11.570","Text":"You all know that different parts of the skin are sensitive in different ways."},{"Start":"01:11.570 ","End":"01:15.545","Text":"Let\u0027s look at different kinds of chemoreceptors,"},{"Start":"01:15.545 ","End":"01:18.550","Text":"those that are sensitive to different chemicals."},{"Start":"01:18.550 ","End":"01:22.330","Text":"They\u0027re specialized cell groups and these receptors,"},{"Start":"01:22.330 ","End":"01:24.404","Text":"so let\u0027s say for instance in the heart,"},{"Start":"01:24.404 ","End":"01:30.440","Text":"we\u0027ll have something which is sensitive to pressure, a baroreceptor pressure."},{"Start":"01:30.440 ","End":"01:32.090","Text":"There\u0027ll be others, for instance,"},{"Start":"01:32.090 ","End":"01:36.440","Text":"that are involved in changes in carbon dioxide and oxygen"},{"Start":"01:36.440 ","End":"01:41.540","Text":"pH and so on in order to maintain the appropriate levels in the blood,"},{"Start":"01:41.540 ","End":"01:43.475","Text":"giving the information to the brain,"},{"Start":"01:43.475 ","End":"01:46.055","Text":"which can then change"},{"Start":"01:46.055 ","End":"01:54.325","Text":"the different organs in the body to maintain constant carbon dioxide, oxygen, and pH."},{"Start":"01:54.325 ","End":"01:57.530","Text":"There are central chemoreceptors that are located"},{"Start":"01:57.530 ","End":"02:00.800","Text":"within the brain that are sensitive to these things."},{"Start":"02:00.800 ","End":"02:03.530","Text":"As I said, they\u0027ll send out the signals."},{"Start":"02:03.530 ","End":"02:06.380","Text":"In addition, there are peripheral chemoreceptors,"},{"Start":"02:06.380 ","End":"02:09.365","Text":"ones that are outside the brain for instance,"},{"Start":"02:09.365 ","End":"02:15.710","Text":"these aortic receptors, as I discussed earlier."},{"Start":"02:15.710 ","End":"02:20.295","Text":"They too can even monitor the same things because"},{"Start":"02:20.295 ","End":"02:27.095","Text":"it\u0027s particularly important that the heart gets the right kind of blood."},{"Start":"02:27.095 ","End":"02:30.765","Text":"Let\u0027s look now at electroreceptors."},{"Start":"02:30.765 ","End":"02:36.780","Text":"Electroreceptors are very specialized receptors and there are some fish,"},{"Start":"02:36.780 ","End":"02:39.170","Text":"for instance, that have these in their nose,"},{"Start":"02:39.170 ","End":"02:43.430","Text":"and they can detect electromagnetic energy directly through the water,"},{"Start":"02:43.430 ","End":"02:45.245","Text":"either as lights, electricity,"},{"Start":"02:45.245 ","End":"02:50.944","Text":"some even magnetism, so that they can either find prey more easily,"},{"Start":"02:50.944 ","End":"02:54.530","Text":"they can detect an electric field that are generated by their prey."},{"Start":"02:54.530 ","End":"02:59.330","Text":"As you know, there are some birds which navigates"},{"Start":"02:59.330 ","End":"03:04.370","Text":"the Earth during their migration using the Earth\u0027s magnetic field,"},{"Start":"03:04.370 ","End":"03:07.445","Text":"so that has to be sensed somehow."},{"Start":"03:07.445 ","End":"03:10.175","Text":"Let\u0027s now talk about thermoreceptors."},{"Start":"03:10.175 ","End":"03:14.270","Text":"Those are receptors that can detect temperature."},{"Start":"03:14.270 ","End":"03:19.155","Text":"There are warmth receptors and there are cold receptors."},{"Start":"03:19.155 ","End":"03:24.315","Text":"Let\u0027s look at the warm receptors to begin with."},{"Start":"03:24.315 ","End":"03:31.165","Text":"The warmth receptors in humans have a very narrow temperature range."},{"Start":"03:31.165 ","End":"03:33.220","Text":"Say between 30 and 50,"},{"Start":"03:33.220 ","End":"03:36.605","Text":"you feel warm and they begin to fire at about 30."},{"Start":"03:36.605 ","End":"03:39.230","Text":"Yes and then if they get higher than 45,"},{"Start":"03:39.230 ","End":"03:40.520","Text":"you start feeling pain."},{"Start":"03:40.520 ","End":"03:43.370","Text":"That\u0027s when you start feeling something burning."},{"Start":"03:43.370 ","End":"03:45.545","Text":"The cold receptors, on the other hand,"},{"Start":"03:45.545 ","End":"03:52.415","Text":"have a very large temperature range and even overlap somewhere with the warmth receptor."},{"Start":"03:52.415 ","End":"03:56.540","Text":"That\u0027s say between about 5-45,"},{"Start":"03:56.540 ","End":"04:02.430","Text":"something like that, but there\u0027s a peak which is much broader."},{"Start":"04:02.430 ","End":"04:05.630","Text":"They dominate the response to cold temperature,"},{"Start":"04:05.630 ","End":"04:08.180","Text":"but they\u0027re also active in warm temperatures,"},{"Start":"04:08.180 ","End":"04:09.810","Text":"as I said before,"},{"Start":"04:09.810 ","End":"04:13.820","Text":"and their increased firing is between 20 and 30,"},{"Start":"04:13.820 ","End":"04:16.085","Text":"that\u0027s when we\u0027re most comfortable."},{"Start":"04:16.085 ","End":"04:18.680","Text":"Below 15 or so,"},{"Start":"04:18.680 ","End":"04:21.215","Text":"the firing stops altogether."},{"Start":"04:21.215 ","End":"04:27.260","Text":"Interestingly, in snakes, some of them have these thermoreceptors and"},{"Start":"04:27.260 ","End":"04:33.405","Text":"they can use this to detect warm-blooded animals that might be their prey."},{"Start":"04:33.405 ","End":"04:37.605","Text":"That\u0027s another kind of receptor."},{"Start":"04:37.605 ","End":"04:42.840","Text":"It will receive the infrared waves,"},{"Start":"04:42.840 ","End":"04:45.070","Text":"that\u0027s the heat from prey,"},{"Start":"04:45.070 ","End":"04:48.625","Text":"and then that\u0027ll help them find their prey."},{"Start":"04:48.625 ","End":"04:51.760","Text":"Lastly, let\u0027s talk about nociceptors."},{"Start":"04:51.760 ","End":"04:55.870","Text":"Those are receptors that are sensitive to"},{"Start":"04:55.870 ","End":"05:00.220","Text":"various kinds of pressure that cause pain. Let\u0027s see."},{"Start":"05:00.220 ","End":"05:04.490","Text":"A thumbtack in your finger will cause pain."},{"Start":"05:04.490 ","End":"05:07.960","Text":"These are particular receptors that cause pain."},{"Start":"05:07.960 ","End":"05:11.980","Text":"They\u0027re attached to the nerves that go into"},{"Start":"05:11.980 ","End":"05:16.180","Text":"the spinal cord that elicits a response immediately as a reflex,"},{"Start":"05:16.180 ","End":"05:17.905","Text":"let\u0027s say to move your hands."},{"Start":"05:17.905 ","End":"05:20.860","Text":"Usually these, of course,"},{"Start":"05:20.860 ","End":"05:25.310","Text":"these nociceptors respond to harmful conditions."},{"Start":"05:25.310 ","End":"05:27.290","Text":"Yes, to harmful conditions."},{"Start":"05:27.290 ","End":"05:29.540","Text":"They can be heat, pressure,"},{"Start":"05:29.540 ","End":"05:32.015","Text":"things that are going to hurt you a lot,"},{"Start":"05:32.015 ","End":"05:33.739","Text":"or sometimes even chemicals."},{"Start":"05:33.739 ","End":"05:37.580","Text":"Yes, the receptive fields in these things are very small."},{"Start":"05:37.580 ","End":"05:40.370","Text":"Remember the example that I gave where you have"},{"Start":"05:40.370 ","End":"05:43.310","Text":"lots of receptors that are close together in the hand,"},{"Start":"05:43.310 ","End":"05:45.266","Text":"whereas in the back they\u0027ll be far apart,"},{"Start":"05:45.266 ","End":"05:48.905","Text":"that way you could tell exactly where the pain is coming from"},{"Start":"05:48.905 ","End":"05:54.530","Text":"and those have very important role in stimulus localization."},{"Start":"05:54.530 ","End":"06:02.160","Text":"We know exactly what to move away from the noxious stimulus."}],"ID":30003}],"Thumbnail":null,"ID":284104},{"Name":"Somatosensation","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Receptors in the Skin","Duration":"5m 47s","ChapterTopicVideoID":28512,"CourseChapterTopicPlaylistID":284105,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.360","Text":"I\u0027m really glad you\u0027re back now for this video,"},{"Start":"00:03.360 ","End":"00:07.200","Text":"so that we can continue discussing sensations."},{"Start":"00:07.200 ","End":"00:11.550","Text":"Remember, we discussed receptors in the previous videos and now we\u0027re going"},{"Start":"00:11.550 ","End":"00:18.570","Text":"to concentrate on somatosensation."},{"Start":"00:18.570 ","End":"00:20.550","Text":"What is somatosensation?"},{"Start":"00:20.550 ","End":"00:26.420","Text":"Sensation that is received from the skin and mucous membranes, limbs, and joints."},{"Start":"00:26.420 ","End":"00:30.980","Text":"In other words, it\u0027s the things that you feel right in"},{"Start":"00:30.980 ","End":"00:33.380","Text":"different parts of your body as opposed to"},{"Start":"00:33.380 ","End":"00:35.990","Text":"things that you see or that you hear and so on."},{"Start":"00:35.990 ","End":"00:38.119","Text":"These are things that you feel."},{"Start":"00:38.119 ","End":"00:46.540","Text":"As you\u0027ll see, there are different receptors that are involved in that sensation."},{"Start":"00:46.540 ","End":"00:51.620","Text":"These sensations occur all over the exterior of the body and as"},{"Start":"00:51.620 ","End":"00:56.995","Text":"well in some interior locations but for the most part it\u0027s at the exterior."},{"Start":"00:56.995 ","End":"01:00.050","Text":"We have different receptors,"},{"Start":"01:00.050 ","End":"01:02.990","Text":"as you can see here, the different receptors."},{"Start":"01:02.990 ","End":"01:05.090","Text":"There\u0027s some that have free nerve endings,"},{"Start":"01:05.090 ","End":"01:06.560","Text":"there are some that are encapsulated,"},{"Start":"01:06.560 ","End":"01:08.270","Text":"as we\u0027ve discussed earlier."},{"Start":"01:08.270 ","End":"01:14.945","Text":"Some have particular sensory cells that then are connected to the nervous cell,"},{"Start":"01:14.945 ","End":"01:19.785","Text":"which is going to deliver the signal to the central nervous system."},{"Start":"01:19.785 ","End":"01:26.180","Text":"Some of these sensory cells have particular peripheral processes,"},{"Start":"01:26.180 ","End":"01:30.510","Text":"that is, external pieces that are going to be doing the feeling."},{"Start":"01:30.510 ","End":"01:33.200","Text":"These are embedded in the skin,"},{"Start":"01:33.200 ","End":"01:35.525","Text":"mucous membranes, muscles, joints, internal,"},{"Start":"01:35.525 ","End":"01:41.090","Text":"any place that you can actually feel something going on."},{"Start":"01:41.090 ","End":"01:47.480","Text":"Now let\u0027s look at the skin where most of these are found in some more detail,"},{"Start":"01:47.480 ","End":"01:53.720","Text":"and we\u0027ll see what receptors there are in different parts of the skin."},{"Start":"01:53.720 ","End":"01:59.195","Text":"First of all, the skin as you know has numerous different layers."},{"Start":"01:59.195 ","End":"02:04.870","Text":"There\u0027s the epidermis, which is the outermost layer and it\u0027s pretty much dead."},{"Start":"02:04.870 ","End":"02:08.330","Text":"It\u0027s composed of keratin primarily in some cells underneath,"},{"Start":"02:08.330 ","End":"02:12.200","Text":"which are not so alive because they don\u0027t have a blood supply."},{"Start":"02:12.200 ","End":"02:14.075","Text":"Under that is the dermis."},{"Start":"02:14.075 ","End":"02:16.770","Text":"This is where things are alive."},{"Start":"02:16.770 ","End":"02:19.190","Text":"Yes, and It contains blood vessels,"},{"Start":"02:19.190 ","End":"02:21.545","Text":"sweat glands, hair follicles, all things."},{"Start":"02:21.545 ","End":"02:26.810","Text":"You\u0027ll see these receptors as well are going to be in the dermis."},{"Start":"02:26.810 ","End":"02:30.980","Text":"Under the dermis is the hypodermis,"},{"Start":"02:30.980 ","End":"02:37.550","Text":"which is this fatty layer that gives you the feeling of strength to the skin,"},{"Start":"02:37.550 ","End":"02:41.720","Text":"which is on the outside and it also contains blood vessels, connective tissue,"},{"Start":"02:41.720 ","End":"02:44.570","Text":"and the beginnings of the neurons,"},{"Start":"02:44.570 ","End":"02:49.100","Text":"the axons of the neurons which are going to extend into it."},{"Start":"02:49.100 ","End":"02:53.855","Text":"Now let\u0027s look at a little bit of a different picture of the skin."},{"Start":"02:53.855 ","End":"02:56.360","Text":"You can see here that it\u0027s somewhat of"},{"Start":"02:56.360 ","End":"03:04.175","Text":"a different representation that has in it the same features as we saw before."},{"Start":"03:04.175 ","End":"03:10.580","Text":"There is the epidermis and then there\u0027s the dermis as we saw earlier."},{"Start":"03:10.580 ","End":"03:15.905","Text":"Now, inside this dermis are various receptors,"},{"Start":"03:15.905 ","End":"03:18.900","Text":"as you can see here, and nerve endings."},{"Start":"03:18.900 ","End":"03:23.500","Text":"Let\u0027s start our discussion with these Merkel\u0027s disks."},{"Start":"03:23.500 ","End":"03:27.440","Text":"They are very densely distributed in the fingertips and the lips,"},{"Start":"03:27.440 ","End":"03:32.450","Text":"and they respond to very light touch."},{"Start":"03:32.450 ","End":"03:35.720","Text":"This is when you feel something touching you,"},{"Start":"03:35.720 ","End":"03:39.055","Text":"like in your fingers for instance or other places."},{"Start":"03:39.055 ","End":"03:43.690","Text":"These are the nerve endings that are being"},{"Start":"03:43.690 ","End":"03:48.560","Text":"stimulated with very specific structures called these Merkel\u0027s disks."},{"Start":"03:48.560 ","End":"03:52.870","Text":"Then we have other sensors called Meissner\u0027s corpuscles,"},{"Start":"03:52.870 ","End":"03:55.135","Text":"and they\u0027re found in other places as well."},{"Start":"03:55.135 ","End":"03:57.250","Text":"For instance, the eyelids."},{"Start":"03:57.250 ","End":"04:01.615","Text":"They also responds to very light,"},{"Start":"04:01.615 ","End":"04:03.640","Text":"fine touch, and pressure,"},{"Start":"04:03.640 ","End":"04:07.820","Text":"but their structure is somewhat different."},{"Start":"04:07.820 ","End":"04:11.100","Text":"Finally or next, I should say,"},{"Start":"04:11.100 ","End":"04:13.779","Text":"we have these Ruffini endings,"},{"Start":"04:13.779 ","End":"04:21.915","Text":"another structure, and those detect skin stretch, deformations within joints."},{"Start":"04:21.915 ","End":"04:23.805","Text":"When you\u0027re being stressed,"},{"Start":"04:23.805 ","End":"04:27.265","Text":"it\u0027s not exactly the same thing as being touched."},{"Start":"04:27.265 ","End":"04:37.040","Text":"There are in fact different receptors at the nerve endings which are sensing this,"},{"Start":"04:37.040 ","End":"04:41.465","Text":"so that you can differentiate between just touch and stretch."},{"Start":"04:41.465 ","End":"04:46.600","Text":"Next, we have these Pacinian corpuscles."},{"Start":"04:47.420 ","End":"04:52.610","Text":"They are a bit deeper inside the skin and they"},{"Start":"04:52.610 ","End":"04:58.325","Text":"can sense transient pressure and also high frequency vibrations."},{"Start":"04:58.325 ","End":"05:08.030","Text":"It\u0027s a different sensor to sense a difference signal of pressure rather than just touch."},{"Start":"05:08.030 ","End":"05:11.285","Text":"Now you\u0027ll notice that there is something we have not discussed,"},{"Start":"05:11.285 ","End":"05:14.480","Text":"which are these Krause end bulbs."},{"Start":"05:14.480 ","End":"05:16.865","Text":"These Krause end bulbs,"},{"Start":"05:16.865 ","End":"05:19.970","Text":"it seems don\u0027t so much response to touch,"},{"Start":"05:19.970 ","End":"05:23.090","Text":"but they respond to temperature."},{"Start":"05:23.090 ","End":"05:25.665","Text":"Those are thermoreceptors."},{"Start":"05:25.665 ","End":"05:28.625","Text":"They\u0027re sensitive to cold primarily,"},{"Start":"05:28.625 ","End":"05:36.830","Text":"and they\u0027re activated by cool temperatures under the temperature of about 20."},{"Start":"05:36.830 ","End":"05:38.705","Text":"In the next video,"},{"Start":"05:38.705 ","End":"05:47.340","Text":"we\u0027ll discuss in greater detail other sensors that are found in other organs."}],"ID":30006},{"Watched":false,"Name":"Somatosensation in Muscle Heart and Skin","Duration":"7m 45s","ChapterTopicVideoID":28513,"CourseChapterTopicPlaylistID":284105,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.695","Text":"Let\u0027s continue with our discussion of somatosensation."},{"Start":"00:04.695 ","End":"00:06.225","Text":"In the previous video,"},{"Start":"00:06.225 ","End":"00:09.270","Text":"we spoke about different receptors that are in"},{"Start":"00:09.270 ","End":"00:13.620","Text":"the skin and we\u0027ll return to them in this video as well but"},{"Start":"00:13.620 ","End":"00:17.370","Text":"let\u0027s begin this video with discussion of"},{"Start":"00:17.370 ","End":"00:22.875","Text":"receptors that are found in the muscles and in the tendons."},{"Start":"00:22.875 ","End":"00:25.650","Text":"Now, the muscle spindle fibers,"},{"Start":"00:25.650 ","End":"00:30.240","Text":"that\u0027s the muscles that you can see here or enlarged over here,"},{"Start":"00:30.240 ","End":"00:37.215","Text":"have sensory neurons in them as well and they can detect stretch of those muscles."},{"Start":"00:37.215 ","End":"00:42.755","Text":"When you\u0027re stretching, you feel some pain but it\u0027s not regular painless,"},{"Start":"00:42.755 ","End":"00:44.450","Text":"say, touching with a needle,"},{"Start":"00:44.450 ","End":"00:45.950","Text":"it feels a little bit different."},{"Start":"00:45.950 ","End":"00:49.490","Text":"There are specific sensory neurons that are found"},{"Start":"00:49.490 ","End":"00:53.660","Text":"inside this muscle that allow you to feel that stretch."},{"Start":"00:53.660 ","End":"00:59.405","Text":"In addition, you have tendons at the ends of your muscles as you know."},{"Start":"00:59.405 ","End":"01:03.095","Text":"There is something called a Golgi tendon organ."},{"Start":"01:03.095 ","End":"01:07.855","Text":"These are receptors that detect the force of muscle contraction,"},{"Start":"01:07.855 ","End":"01:09.950","Text":"so you can feel here,"},{"Start":"01:09.950 ","End":"01:18.644","Text":"you can feel when your muscle is being extended or when it\u0027s being contracted and that"},{"Start":"01:18.644 ","End":"01:28.045","Text":"is sensed by these Golgi tendon organs or by the neurons which are within that organ."},{"Start":"01:28.045 ","End":"01:35.330","Text":"There are these unconscious proprioceptive signals"},{"Start":"01:35.330 ","End":"01:39.765","Text":"that run from the spinal cord to the cerebellum rather than the thalamus."},{"Start":"01:39.765 ","End":"01:45.395","Text":"Most of the signals we learned earlier go through the thalamus where there is"},{"Start":"01:45.395 ","End":"01:51.155","Text":"a clearinghouse deciding what sensations go to what kind of the brain."},{"Start":"01:51.155 ","End":"01:59.420","Text":"But these signals run directly into the cerebellum and therefore you can get more of"},{"Start":"01:59.420 ","End":"02:07.835","Text":"an integrated feeling of what your position is in these proprioceptive signals."},{"Start":"02:07.835 ","End":"02:10.835","Text":"Now let\u0027s look at other kinds of sensors."},{"Start":"02:10.835 ","End":"02:18.195","Text":"There are sensors that are called baroreceptors that can detect pressure."},{"Start":"02:18.195 ","End":"02:20.180","Text":"Baro is pressure."},{"Start":"02:20.180 ","End":"02:24.425","Text":"What are we talking about? We\u0027re talking about blood pressure."},{"Start":"02:24.425 ","End":"02:28.790","Text":"Our heart is pumping,"},{"Start":"02:28.790 ","End":"02:32.330","Text":"producing pressure in both the heart and in"},{"Start":"02:32.330 ","End":"02:36.880","Text":"the arteries which are emanating from the heart."},{"Start":"02:36.880 ","End":"02:46.189","Text":"That pressure then, or the level of the pressure is sent to the medulla of the brainstem."},{"Start":"02:46.189 ","End":"02:48.005","Text":"In the medulla here,"},{"Start":"02:48.005 ","End":"02:52.280","Text":"there are these cells which can then send"},{"Start":"02:52.280 ","End":"02:56.810","Text":"signals back to the heart through the vagus nerve,"},{"Start":"02:56.810 ","End":"03:01.310","Text":"which can adjust the heart rate so that the blood pressure is"},{"Start":"03:01.310 ","End":"03:06.235","Text":"maintained at a pressure which is appropriate to the organism."},{"Start":"03:06.235 ","End":"03:13.070","Text":"These pressures can be detected in different organs as well."},{"Start":"03:13.070 ","End":"03:15.260","Text":"They, as we said,"},{"Start":"03:15.260 ","End":"03:18.905","Text":"are baroreceptors, so they detect pressure."},{"Start":"03:18.905 ","End":"03:21.440","Text":"Of course, the blood pressure is important to"},{"Start":"03:21.440 ","End":"03:25.100","Text":"monitor because if the blood pressure is too low,"},{"Start":"03:25.100 ","End":"03:27.800","Text":"we won\u0027t get enough blood supply in particular to the brain,"},{"Start":"03:27.800 ","End":"03:32.440","Text":"to begin with, and if it\u0027s too high, things can burst."},{"Start":"03:32.440 ","End":"03:38.600","Text":"Actually, there\u0027s another kind of baroreceptor that is important"},{"Start":"03:38.600 ","End":"03:44.765","Text":"for us to remember and those also can detect the degree of lung expansion."},{"Start":"03:44.765 ","End":"03:49.535","Text":"Of course, there is air pressure in our lungs"},{"Start":"03:49.535 ","End":"03:55.335","Text":"and that is detected by baroreceptors as well."},{"Start":"03:55.335 ","End":"04:03.170","Text":"Now let\u0027s return back to the skin and look in more detail at these mechanoreceptors,"},{"Start":"04:03.170 ","End":"04:06.440","Text":"the ones that can detect pressure or"},{"Start":"04:06.440 ","End":"04:10.595","Text":"light touch or heavier touch and that thing that we discussed earlier,"},{"Start":"04:10.595 ","End":"04:12.260","Text":"there were in the hands and if you remember,"},{"Start":"04:12.260 ","End":"04:16.970","Text":"we discussed different kinds of receptors."},{"Start":"04:16.970 ","End":"04:20.120","Text":"What we\u0027re going to see here is that these receptors are"},{"Start":"04:20.120 ","End":"04:23.150","Text":"distributed in different places in"},{"Start":"04:23.150 ","End":"04:29.480","Text":"the hands and they are distributed with different densities as well."},{"Start":"04:29.480 ","End":"04:33.860","Text":"They can be very dense in particular areas, say the fingertips,"},{"Start":"04:33.860 ","End":"04:36.890","Text":"where it\u0027s very important to be able to distinguish where things"},{"Start":"04:36.890 ","End":"04:41.210","Text":"are and less densely in other places."},{"Start":"04:41.210 ","End":"04:46.535","Text":"The touch receptors are less dense in the skin covered interestingly,"},{"Start":"04:46.535 ","End":"04:47.690","Text":"by any type of hair,"},{"Start":"04:47.690 ","End":"04:52.800","Text":"you know that the palms of your hands have no hair on them."},{"Start":"04:52.800 ","End":"04:56.660","Text":"In that region, we have a greater sensation."},{"Start":"04:56.660 ","End":"05:03.560","Text":"Those areas of the hands that have no hair on them are called glabrous skin."},{"Start":"05:03.560 ","End":"05:07.790","Text":"The fingertips and also the lips have no hair on them."},{"Start":"05:07.790 ","End":"05:14.255","Text":"The Merkel cells and the Meissner\u0027s corpuscles have the smallest response field,"},{"Start":"05:14.255 ","End":"05:20.004","Text":"that is the area that is affected or where these nerves are,"},{"Start":"05:20.004 ","End":"05:21.830","Text":"it can be very concentrated in"},{"Start":"05:21.830 ","End":"05:26.825","Text":"particular places and therefore we get a very specific feeling."},{"Start":"05:26.825 ","End":"05:29.525","Text":"On the other hand, thermoreception by"},{"Start":"05:29.525 ","End":"05:35.120","Text":"the Krause end bulbs that we discussed earlier can end as well as"},{"Start":"05:35.120 ","End":"05:39.305","Text":"the Ruffini endings are more dispersed and"},{"Start":"05:39.305 ","End":"05:45.710","Text":"they are located further inside the dermis as well as in other places,"},{"Start":"05:45.710 ","End":"05:48.245","Text":"for instance, in the skeletal muscles, liver,"},{"Start":"05:48.245 ","End":"05:51.835","Text":"and in the hypothalamus even."},{"Start":"05:51.835 ","End":"05:57.200","Text":"The temperature information travels from the spinal cord through the thalamus,"},{"Start":"05:57.200 ","End":"06:05.315","Text":"so that\u0027s like a lot of other signals to the primary somatosensory cortex."},{"Start":"06:05.315 ","End":"06:08.855","Text":"If the stimulus is too intense,"},{"Start":"06:08.855 ","End":"06:12.410","Text":"instead of feeling touch, you feel pain."},{"Start":"06:12.410 ","End":"06:19.884","Text":"Interestingly, that stimulus is carried through the same pathway as the touch is."},{"Start":"06:19.884 ","End":"06:27.685","Text":"Pain is neural processing of injurious stimuli in response to shoot damage."},{"Start":"06:27.685 ","End":"06:29.195","Text":"As you can see here,"},{"Start":"06:29.195 ","End":"06:32.315","Text":"you\u0027ll have a sensory neuron in the skin,"},{"Start":"06:32.315 ","End":"06:36.650","Text":"which then sends its information through the medulla"},{"Start":"06:36.650 ","End":"06:42.900","Text":"into the cortex where the pain is processed."},{"Start":"06:42.900 ","End":"06:48.080","Text":"This can be caused by harmless stimuli that also mimic damaging stimuli."},{"Start":"06:48.080 ","End":"06:54.335","Text":"For instance, some people are very sensitive to spicy food or hot food,"},{"Start":"06:54.335 ","End":"06:59.360","Text":"and they withdraw from it even though it\u0027s really not dangerous at all."},{"Start":"06:59.360 ","End":"07:02.240","Text":"But the sensation can be the same."},{"Start":"07:02.240 ","End":"07:06.425","Text":"The pain does not start until it\u0027s communicated to the brain."},{"Start":"07:06.425 ","End":"07:11.330","Text":"Therefore, anesthetics can interfere with"},{"Start":"07:11.330 ","End":"07:18.005","Text":"this path and that\u0027s the way that we can say have teeth pulled or other work,"},{"Start":"07:18.005 ","End":"07:24.940","Text":"which is done in our system when we are either partially or completely anesthetized."},{"Start":"07:24.940 ","End":"07:29.210","Text":"Most axons carrying nociceptive information,"},{"Start":"07:29.210 ","End":"07:34.925","Text":"that\u0027s information that causes pain into the brain do project to the thalamus,"},{"Start":"07:34.925 ","End":"07:36.290","Text":"go through the thalamus,"},{"Start":"07:36.290 ","End":"07:39.485","Text":"and the signal undergoes final processing."},{"Start":"07:39.485 ","End":"07:45.210","Text":"Finally, in this somatosensory cortex."}],"ID":30007}],"Thumbnail":null,"ID":284105},{"Name":"Taste and Smell","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Taste and Smell Work Together","Duration":"6m 34s","ChapterTopicVideoID":28514,"CourseChapterTopicPlaylistID":284106,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.120","Text":"Since you\u0027re back, you must be interested in taste and smell."},{"Start":"00:06.120 ","End":"00:12.630","Text":"We\u0027ve been discussing receptors that are primarily have been in the skin,"},{"Start":"00:12.630 ","End":"00:14.370","Text":"or in the heart,"},{"Start":"00:14.370 ","End":"00:20.340","Text":"or in muscle that sense various kinds of touch,"},{"Start":"00:20.340 ","End":"00:23.055","Text":"of pressure, of 1 sort or another."},{"Start":"00:23.055 ","End":"00:29.970","Text":"Now we\u0027re going to be discussing receptors that can sense different kinds of chemicals,"},{"Start":"00:29.970 ","End":"00:34.970","Text":"whether they be in the food that we eat that causes us to taste"},{"Start":"00:34.970 ","End":"00:41.285","Text":"things that\u0027s called gustation or to smell things that\u0027s called olfaction."},{"Start":"00:41.285 ","End":"00:48.710","Text":"These different senses of taste and smell are quite interconnected as you know."},{"Start":"00:48.710 ","End":"00:55.505","Text":"The taste receptors are going to be found on our tongue,"},{"Start":"00:55.505 ","End":"01:01.115","Text":"of course, and that the signals from them are going to be transmitted to the brain."},{"Start":"01:01.115 ","End":"01:09.942","Text":"The sensors for smell are found inside our sinuses in the nasal cavity."},{"Start":"01:09.942 ","End":"01:14.589","Text":"Those signals are also going to be sent to the same place,"},{"Start":"01:14.589 ","End":"01:16.610","Text":"the smell and taste center,"},{"Start":"01:16.610 ","End":"01:17.930","Text":"which is in our brain,"},{"Start":"01:17.930 ","End":"01:22.430","Text":"and those 2 different kinds of signals will then"},{"Start":"01:22.430 ","End":"01:27.080","Text":"be integrated and will give us a sense of flavor."},{"Start":"01:27.080 ","End":"01:28.820","Text":"Now in terrestrial animals,"},{"Start":"01:28.820 ","End":"01:34.070","Text":"that is animals that are living on the ground as opposed to those that are in the water,"},{"Start":"01:34.070 ","End":"01:36.350","Text":"gustation, or taste,"},{"Start":"01:36.350 ","End":"01:40.580","Text":"is reliant on the detection of different chemicals that are"},{"Start":"01:40.580 ","End":"01:45.880","Text":"called tastants that are going to be dissolved on our tongue,"},{"Start":"01:45.880 ","End":"01:48.080","Text":"and you\u0027ll see the receptors on our tongue,"},{"Start":"01:48.080 ","End":"01:49.955","Text":"which is, you\u0027re going to sense them."},{"Start":"01:49.955 ","End":"01:52.580","Text":"On the other hand, olfaction,"},{"Start":"01:52.580 ","End":"01:57.845","Text":"or smell, is reliant on detection of odorants, that is,"},{"Start":"01:57.845 ","End":"02:01.670","Text":"chemicals that are in the air that are"},{"Start":"02:01.670 ","End":"02:06.920","Text":"vaporized that we breathe in through our nose and that are"},{"Start":"02:06.920 ","End":"02:16.705","Text":"going to be dissolved in the mucous membrane that is on our olfactory bulb."},{"Start":"02:16.705 ","End":"02:19.969","Text":"These, in a sense, are similar,"},{"Start":"02:19.969 ","End":"02:24.590","Text":"and they are going to result in our sense of flavor,"},{"Start":"02:24.590 ","End":"02:25.880","Text":"as we said before."},{"Start":"02:25.880 ","End":"02:29.240","Text":"Interestingly, in animals that live in water,"},{"Start":"02:29.240 ","End":"02:32.120","Text":"in aquatic animals, there\u0027s no distinction"},{"Start":"02:32.120 ","End":"02:35.585","Text":"between taste and smell because everything is dissolved."},{"Start":"02:35.585 ","End":"02:38.675","Text":"Now what are the primary tastes that we have?"},{"Start":"02:38.675 ","End":"02:41.870","Text":"They are sweet, sour, bitter,"},{"Start":"02:41.870 ","End":"02:45.645","Text":"salty, and umami. What\u0027s umami?"},{"Start":"02:45.645 ","End":"02:48.710","Text":"Umami are these taste receptors that typically"},{"Start":"02:48.710 ","End":"02:52.310","Text":"respond to chemicals that are called glutamates."},{"Start":"02:52.310 ","End":"02:57.295","Text":"Glutamates are things that are found in fish,"},{"Start":"02:57.295 ","End":"03:01.500","Text":"in various kinds of meats,"},{"Start":"03:01.500 ","End":"03:03.305","Text":"large amounts of it."},{"Start":"03:03.305 ","End":"03:08.254","Text":"These are things that contain large amounts of protein."},{"Start":"03:08.254 ","End":"03:13.280","Text":"Therefore, it\u0027s adaptive for us because we want to be able to"},{"Start":"03:13.280 ","End":"03:15.950","Text":"distinguish foods that are particularly good for"},{"Start":"03:15.950 ","End":"03:19.190","Text":"us and it\u0027ll give us a supply of protein."},{"Start":"03:19.190 ","End":"03:25.580","Text":"The adaptive value of being able to distinguish umami in foods is 1 way"},{"Start":"03:25.580 ","End":"03:32.270","Text":"that we can distinguish them without even knowing it which foods are high in protein."},{"Start":"03:32.270 ","End":"03:36.140","Text":"Let\u0027s have a look at the different chemicals that are involved in"},{"Start":"03:36.140 ","End":"03:41.080","Text":"giving us different kinds of odors."},{"Start":"03:41.080 ","End":"03:45.200","Text":"There are all sorts of volatilized chemical compounds,"},{"Start":"03:45.200 ","End":"03:48.500","Text":"things that are dissolved in the air,"},{"Start":"03:48.500 ","End":"03:51.470","Text":"the simple chemicals, as you can see,"},{"Start":"03:51.470 ","End":"03:58.085","Text":"which cause different flavors or actually cause different smells."},{"Start":"03:58.085 ","End":"03:59.765","Text":"So you can see, for instance,"},{"Start":"03:59.765 ","End":"04:05.795","Text":"that isoamyl acetate is the primary chemical which gives us the smell of bananas,"},{"Start":"04:05.795 ","End":"04:10.010","Text":"whereas mint is methyl salicylate."},{"Start":"04:10.010 ","End":"04:12.710","Text":"It gives us a sense of mint."},{"Start":"04:12.710 ","End":"04:14.810","Text":"So when you know about artificial flavors,"},{"Start":"04:14.810 ","End":"04:18.830","Text":"all that is really is flavorings that are"},{"Start":"04:18.830 ","End":"04:23.810","Text":"made in which they put these chemicals in that might be artificially created,"},{"Start":"04:23.810 ","End":"04:29.310","Text":"but they are the same chemicals as you have in natural products."},{"Start":"04:29.310 ","End":"04:32.570","Text":"Therefore, they will give the sensation"},{"Start":"04:32.570 ","End":"04:36.215","Text":"or the smell of something that we are familiar with."},{"Start":"04:36.215 ","End":"04:37.580","Text":"A lot of times, of course,"},{"Start":"04:37.580 ","End":"04:42.360","Text":"there will be combinations of these odorants."},{"Start":"04:42.360 ","End":"04:45.200","Text":"Obviously, if there are no odorants, that is,"},{"Start":"04:45.200 ","End":"04:48.920","Text":"if a substance does not release molecules into the air,"},{"Start":"04:48.920 ","End":"04:50.555","Text":"then it doesn\u0027t smell."},{"Start":"04:50.555 ","End":"04:54.895","Text":"We only can smell things if there are chemicals in the air."},{"Start":"04:54.895 ","End":"05:02.900","Text":"The odor qualities are often assessed by perception-based ratings. What does that mean?"},{"Start":"05:02.900 ","End":"05:05.690","Text":"That means that different people, of course,"},{"Start":"05:05.690 ","End":"05:10.355","Text":"can smell things to a different degree and a different way."},{"Start":"05:10.355 ","End":"05:11.930","Text":"In a recent study,"},{"Start":"05:11.930 ","End":"05:15.679","Text":"it was suggested the average human is capable of distinguishing"},{"Start":"05:15.679 ","End":"05:19.445","Text":"over a trillion different unique odors."},{"Start":"05:19.445 ","End":"05:21.110","Text":"That\u0027s quite amazing."},{"Start":"05:21.110 ","End":"05:22.580","Text":"But of course, as we\u0027ll see,"},{"Start":"05:22.580 ","End":"05:26.090","Text":"some animals do this even better."},{"Start":"05:26.090 ","End":"05:31.235","Text":"Let\u0027s look at the receptors, the olfactory receptors."},{"Start":"05:31.235 ","End":"05:34.440","Text":"These are chemoreceptors. Where are they found?"},{"Start":"05:34.440 ","End":"05:36.314","Text":"Here\u0027s the nasal passage."},{"Start":"05:36.314 ","End":"05:38.485","Text":"On the top of the nasal passage,"},{"Start":"05:38.485 ","End":"05:43.820","Text":"here we find the region is enlarged."},{"Start":"05:43.820 ","End":"05:49.410","Text":"It has an olfactory epithelium that is responsible for the detection of the odorants."},{"Start":"05:49.410 ","End":"05:51.935","Text":"You see it has a particular structure."},{"Start":"05:51.935 ","End":"05:54.785","Text":"Now let\u0027s discuss that structure."},{"Start":"05:54.785 ","End":"05:57.665","Text":"There are these renewable neurons,"},{"Start":"05:57.665 ","End":"05:58.790","Text":"these various neurons,"},{"Start":"05:58.790 ","End":"06:02.780","Text":"which extend in to the epithelium."},{"Start":"06:02.780 ","End":"06:06.030","Text":"They extend into the bottom here where these receptors are."},{"Start":"06:06.030 ","End":"06:10.130","Text":"Both odors and tastes involve molecules, as we said,"},{"Start":"06:10.130 ","End":"06:13.955","Text":"which are going to stimulate chemoreceptors."},{"Start":"06:13.955 ","End":"06:15.200","Text":"What are chemoreceptors?"},{"Start":"06:15.200 ","End":"06:18.395","Text":"These are going to be receptors that are going to be found down here"},{"Start":"06:18.395 ","End":"06:22.940","Text":"that can bind to particular odors,"},{"Start":"06:22.940 ","End":"06:25.190","Text":"particular chemicals, either in this case,"},{"Start":"06:25.190 ","End":"06:26.825","Text":"where we\u0027re talking about smell,"},{"Start":"06:26.825 ","End":"06:29.360","Text":"and the perception of flavor,"},{"Start":"06:29.360 ","End":"06:33.630","Text":"as we said, is a combination of both taste and smell."}],"ID":30011},{"Watched":false,"Name":"Olfactory Neurons and Pheromones","Duration":"5m 42s","ChapterTopicVideoID":28516,"CourseChapterTopicPlaylistID":284106,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.100","Text":"In the previous video,"},{"Start":"00:02.100 ","End":"00:06.720","Text":"we were discussing taste and smell and how they work together."},{"Start":"00:06.720 ","End":"00:09.420","Text":"So let\u0027s continue that discussion now."},{"Start":"00:09.420 ","End":"00:12.060","Text":"In humans, odorants,"},{"Start":"00:12.060 ","End":"00:16.785","Text":"those are chemicals that are going to be sensed,"},{"Start":"00:16.785 ","End":"00:20.610","Text":"enter the nose and dissolve in the olfactory epithelium,"},{"Start":"00:20.610 ","End":"00:22.260","Text":"as we mentioned earlier,"},{"Start":"00:22.260 ","End":"00:26.160","Text":"that are in the top of the nasal cavity,"},{"Start":"00:26.160 ","End":"00:29.610","Text":"at the bottom of this area that senses it,"},{"Start":"00:29.610 ","End":"00:33.600","Text":"so it\u0027s at the upper portion of the nasal cavity."},{"Start":"00:33.600 ","End":"00:37.050","Text":"The olfactory receptor responds by sending impulses"},{"Start":"00:37.050 ","End":"00:42.160","Text":"directly to this area called the olfactory bulb,"},{"Start":"00:42.350 ","End":"00:45.890","Text":"which is in the brain."},{"Start":"00:45.890 ","End":"00:48.980","Text":"Now, of course, there are different chemical molecules,"},{"Start":"00:48.980 ","End":"00:54.890","Text":"and they fit into different receptor cells creating these different smells."},{"Start":"00:54.890 ","End":"00:57.815","Text":"We\u0027ll see that in more detail in a minute."},{"Start":"00:57.815 ","End":"01:02.645","Text":"The individual odor receptors are broadly tuned"},{"Start":"01:02.645 ","End":"01:07.625","Text":"to be activated by a number of similar odorant structures."},{"Start":"01:07.625 ","End":"01:14.030","Text":"They evolve so that they can sense things which are similar to 1 another."},{"Start":"01:14.030 ","End":"01:16.010","Text":"How many of these do we have?"},{"Start":"01:16.010 ","End":"01:20.480","Text":"Humans have about 12 million olfactory receptors that are"},{"Start":"01:20.480 ","End":"01:26.704","Text":"distributed among only about 200 different receptor types."},{"Start":"01:26.704 ","End":"01:30.140","Text":"On the other hand, animals like dogs, for instance,"},{"Start":"01:30.140 ","End":"01:33.710","Text":"or rabbits have many more olfactory receptors."},{"Start":"01:33.710 ","End":"01:36.550","Text":"They smell things better than we do."},{"Start":"01:36.550 ","End":"01:39.935","Text":"Rabbits have about 100 million olfactory receptors,"},{"Start":"01:39.935 ","End":"01:44.900","Text":"whereas some dogs have even as many as 4 billion."},{"Start":"01:44.900 ","End":"01:47.870","Text":"In addition to that, the overall size of"},{"Start":"01:47.870 ","End":"01:52.745","Text":"the olfactory epithelium also differs greatly between species."},{"Start":"01:52.745 ","End":"01:55.985","Text":"Now let\u0027s go back to the figure that we saw before"},{"Start":"01:55.985 ","End":"01:59.905","Text":"and look in greater detail to see how this works."},{"Start":"01:59.905 ","End":"02:04.750","Text":"There are these bipolar neurons,"},{"Start":"02:06.380 ","End":"02:10.670","Text":"at the end of which there are these dendrites that"},{"Start":"02:10.670 ","End":"02:16.515","Text":"extend into this nasal epithelium here."},{"Start":"02:16.515 ","End":"02:26.360","Text":"Each of them has these chemo receptors in the plasma membrane of these dendrites."},{"Start":"02:26.360 ","End":"02:33.305","Text":"There are receptors there that can recognize particular odorants."},{"Start":"02:33.305 ","End":"02:36.020","Text":"There are different ones."},{"Start":"02:36.020 ","End":"02:45.390","Text":"Each 1 of these neurons contains particular receptors."},{"Start":"02:45.390 ","End":"02:49.280","Text":"Now, at the end of these dendrites,"},{"Start":"02:49.280 ","End":"02:52.880","Text":"there are hair-like cilia and about,"},{"Start":"02:52.880 ","End":"02:54.665","Text":"say 5-20 of them,"},{"Start":"02:54.665 ","End":"03:01.400","Text":"and each of them contains the same receptors for a particular odorant,"},{"Start":"03:01.400 ","End":"03:10.790","Text":"but different neurons will have different receptors in them to different odorants."},{"Start":"03:10.790 ","End":"03:19.840","Text":"Each olfactory sensory neuron has only 1 type of a receptor on its cilia."},{"Start":"03:19.840 ","End":"03:22.280","Text":"It\u0027ll have many of these receptors,"},{"Start":"03:22.280 ","End":"03:23.975","Text":"like you can see here,"},{"Start":"03:23.975 ","End":"03:27.385","Text":"but there\u0027s only 1 type."},{"Start":"03:27.385 ","End":"03:31.340","Text":"Olfactory stimulation is the only sensory information that"},{"Start":"03:31.340 ","End":"03:36.650","Text":"directly reaches the cerebral cortex."},{"Start":"03:36.650 ","End":"03:45.005","Text":"You\u0027ll see in a minute about how these neurons are connected to the cerebral cortex."},{"Start":"03:45.005 ","End":"03:49.265","Text":"In addition to smells that come from the outside,"},{"Start":"03:49.265 ","End":"03:51.230","Text":"some organisms, in fact,"},{"Start":"03:51.230 ","End":"03:54.799","Text":"many organisms create particular smells"},{"Start":"03:54.799 ","End":"03:59.000","Text":"that are then picked up by other members of the same organism."},{"Start":"03:59.000 ","End":"04:01.505","Text":"Those are called pheromones."},{"Start":"04:01.505 ","End":"04:04.820","Text":"It\u0027s a chemical released by an animal that affects the behavior or"},{"Start":"04:04.820 ","End":"04:09.115","Text":"physiology of animals of the same species."},{"Start":"04:09.115 ","End":"04:15.845","Text":"For instance, bees communicate with each other in various different ways,"},{"Start":"04:15.845 ","End":"04:24.320","Text":"primarily, by excreting various chemicals that are recognized by other bees."},{"Start":"04:24.320 ","End":"04:26.825","Text":"Those are called pheromones."},{"Start":"04:26.825 ","End":"04:29.765","Text":"They can attract potential mates,"},{"Start":"04:29.765 ","End":"04:34.890","Text":"deter potential competitors, play roles in mother-infant attachment, and so on."},{"Start":"04:34.890 ","End":"04:40.530","Text":"In fact, it\u0027s thought that even humans create some pheromones."},{"Start":"04:40.580 ","End":"04:42.869","Text":"But in humans,"},{"Start":"04:42.869 ","End":"04:47.540","Text":"there are a lot less important in human behavior than,"},{"Start":"04:47.540 ","End":"04:49.145","Text":"say, with bees."},{"Start":"04:49.145 ","End":"04:54.170","Text":"In some organisms, there are particular organs like"},{"Start":"04:54.170 ","End":"05:01.025","Text":"this vomeronasal organ that\u0027s found in rodents."},{"Start":"05:01.025 ","End":"05:04.550","Text":"Sometimes it\u0027s called a Jacobson\u0027s organ."},{"Start":"05:04.550 ","End":"05:09.290","Text":"Those are organs that are adjacent to the nasal cavity,"},{"Start":"05:09.290 ","End":"05:12.155","Text":"and they are sensitive particularly to pheromones,"},{"Start":"05:12.155 ","End":"05:17.020","Text":"and they\u0027re connected to the nasal cavity by a particular duct."},{"Start":"05:17.020 ","End":"05:20.915","Text":"This VNO, or Jacobson\u0027s organ,"},{"Start":"05:20.915 ","End":"05:25.670","Text":"sends signals to the accessory olfactory bulb and that"},{"Start":"05:25.670 ","End":"05:30.815","Text":"projects directly into the amygdala that\u0027s in the brain."},{"Start":"05:30.815 ","End":"05:34.295","Text":"The signal then continues to the hypothalamus"},{"Start":"05:34.295 ","End":"05:38.555","Text":"that is very important for the behavior of the animal,"},{"Start":"05:38.555 ","End":"05:43.530","Text":"particularly, when it comes to reproductive physiology."}],"ID":30012},{"Watched":false,"Name":"Taste Reception","Duration":"7m 25s","ChapterTopicVideoID":28515,"CourseChapterTopicPlaylistID":284106,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.560","Text":"Now let\u0027s move on in our discussion of taste and"},{"Start":"00:05.560 ","End":"00:10.570","Text":"smell to discussing taste and the reception of taste,"},{"Start":"00:10.570 ","End":"00:13.930","Text":"that is, what are the receptors for taste."},{"Start":"00:13.930 ","End":"00:18.160","Text":"Now, taste is also a little bit of a sensation because"},{"Start":"00:18.160 ","End":"00:22.390","Text":"our tongue is where we have most of our taste buds."},{"Start":"00:22.390 ","End":"00:25.089","Text":"You\u0027ll see that there are different kinds of"},{"Start":"00:25.089 ","End":"00:31.020","Text":"taste buds that are located within papillae on the tongue."},{"Start":"00:31.020 ","End":"00:33.505","Text":"There are different structures on the tongue,"},{"Start":"00:33.505 ","End":"00:34.600","Text":"as we\u0027ll see in a minute."},{"Start":"00:34.600 ","End":"00:37.220","Text":"You can see here in this picture."},{"Start":"00:37.220 ","End":"00:42.870","Text":"The first one, we want to discuss all these Filiform papillae,"},{"Start":"00:42.870 ","End":"00:45.985","Text":"which are just tactile."},{"Start":"00:45.985 ","End":"00:55.570","Text":"That is, they sense the structure or they sense the something about how rough it is,"},{"Start":"00:55.570 ","End":"00:59.905","Text":"what the texture is of something they don\u0027t contain taste cells."},{"Start":"00:59.905 ","End":"01:06.025","Text":"They provide friction that helps the tongue also move substances around."},{"Start":"01:06.025 ","End":"01:11.145","Text":"Then there are fungiform papillae,"},{"Start":"01:11.145 ","End":"01:14.370","Text":"over here that do contain taste buds,"},{"Start":"01:14.370 ","End":"01:19.375","Text":"and they also have receptors in them for both pressure and temperature."},{"Start":"01:19.375 ","End":"01:22.795","Text":"That gives us different kinds of sensations."},{"Start":"01:22.795 ","End":"01:27.770","Text":"Next, we have Circumvallate papillae."},{"Start":"01:28.470 ","End":"01:33.010","Text":"You can see the structure here is similar but a little bit different,"},{"Start":"01:33.010 ","End":"01:35.020","Text":"and they are very large."},{"Start":"01:35.020 ","End":"01:37.795","Text":"They contain up to about a 100 taste buds."},{"Start":"01:37.795 ","End":"01:44.130","Text":"They are primarily found close to the back of the tongue and the shape of a V. Finally,"},{"Start":"01:44.130 ","End":"01:47.200","Text":"there are the Foliate papillae,"},{"Start":"01:47.200 ","End":"01:51.160","Text":"which are found at the edge of the tongue, as you can see here,"},{"Start":"01:51.160 ","End":"01:55.690","Text":"they\u0027re leaf-like and there are located in folds along"},{"Start":"01:55.690 ","End":"02:00.600","Text":"the edges and they contain even more taste buds in their folds."},{"Start":"02:00.600 ","End":"02:05.665","Text":"Different parts of the tongue have different sensors on them."},{"Start":"02:05.665 ","End":"02:09.830","Text":"Let\u0027s look at the taste bud cells themselves."},{"Start":"02:09.830 ","End":"02:16.050","Text":"Each taste bud cell is actually replaced every 10th,"},{"Start":"02:16.050 ","End":"02:18.695","Text":"14 days, every 2 weeks roughly,"},{"Start":"02:18.695 ","End":"02:23.405","Text":"these cells die and are replaced by new ones."},{"Start":"02:23.405 ","End":"02:25.325","Text":"As you can see,"},{"Start":"02:25.325 ","End":"02:29.600","Text":"they have taste receptors at the end of them."},{"Start":"02:29.600 ","End":"02:32.930","Text":"These elongated cells with"},{"Start":"02:32.930 ","End":"02:38.245","Text":"microvilli at the tip and they extend into the taste bud pores."},{"Start":"02:38.245 ","End":"02:42.160","Text":"There\u0027s a pore there as we saw in the previous slide,"},{"Start":"02:42.160 ","End":"02:48.580","Text":"and they are going to be able to sense different kinds of tastes like sweet,"},{"Start":"02:48.580 ","End":"02:51.530","Text":"umami, bitter, sour, salty, and so on."},{"Start":"02:51.530 ","End":"02:53.290","Text":"We\u0027ll see you in a bit how that works."},{"Start":"02:53.290 ","End":"02:56.060","Text":"The tastant are dissolved in the saliva,"},{"Start":"02:56.060 ","End":"03:00.200","Text":"of course, and they are going to stimulate these receptors."},{"Start":"03:00.200 ","End":"03:05.315","Text":"They\u0027re located across the tongue as we saw before."},{"Start":"03:05.315 ","End":"03:11.570","Text":"Now, this taste then is transduced from the receptor through a neuron."},{"Start":"03:11.570 ","End":"03:19.150","Text":"There are different mechanisms that do this depending on the composition of the tastant."},{"Start":"03:19.150 ","End":"03:23.235","Text":"Let\u0027s now look at the nerve here."},{"Start":"03:23.235 ","End":"03:30.290","Text":"The nerve that\u0027s going to be transducing the taste and look first at salts."},{"Start":"03:30.290 ","End":"03:34.415","Text":"Salt is pretty simple because there are sodium ions that"},{"Start":"03:34.415 ","End":"03:40.010","Text":"enter the taste neurons that excites them directly."},{"Start":"03:40.010 ","End":"03:42.770","Text":"It doesn\u0027t have to be a particular receptor for this."},{"Start":"03:42.770 ","End":"03:45.995","Text":"The same thing can happen with calcium entering,"},{"Start":"03:45.995 ","End":"03:49.640","Text":"you get a salty taste this way."},{"Start":"03:49.640 ","End":"03:53.464","Text":"Sour tastant are going to work somewhat differently."},{"Start":"03:53.464 ","End":"03:59.150","Text":"They change pH, there is an increase in hydrogen ion concentrations,"},{"Start":"03:59.150 ","End":"04:05.860","Text":"and those then are going to change the polarization of some of the channels."},{"Start":"04:05.860 ","End":"04:13.460","Text":"That then will be a different a signal that can be passed on to the brain."},{"Start":"04:13.460 ","End":"04:18.695","Text":"Sweet ones require a receptor that involves"},{"Start":"04:18.695 ","End":"04:23.180","Text":"a particular G-protein which is going to start"},{"Start":"04:23.180 ","End":"04:28.715","Text":"a signal transduction pathway that was not necessary before,"},{"Start":"04:28.715 ","End":"04:35.330","Text":"and that\u0027s the same for sweets bitter or umami tastants."},{"Start":"04:35.330 ","End":"04:39.485","Text":"Each of them are going to be a bit different as you just saw."},{"Start":"04:39.485 ","End":"04:42.530","Text":"These tastes instead bind the respective acceptors,"},{"Start":"04:42.530 ","End":"04:48.670","Text":"thereby exciting the specialized neurons that are associated with them."},{"Start":"04:48.670 ","End":"04:51.185","Text":"What about the sensitivity?"},{"Start":"04:51.185 ","End":"04:54.160","Text":"As we know, some people,"},{"Start":"04:54.160 ","End":"04:57.530","Text":"have more taste buds and receptors and they, therefore,"},{"Start":"04:57.530 ","End":"05:01.100","Text":"can perceive flavor better than other people,"},{"Start":"05:01.100 ","End":"05:04.144","Text":"and some of them are sensitive to bitter foods."},{"Start":"05:04.144 ","End":"05:07.640","Text":"Some of the people are sensitive to spicy foods and so on."},{"Start":"05:07.640 ","End":"05:13.010","Text":"That has to do with which receptors they have wear on their tongues."},{"Start":"05:13.010 ","End":"05:16.055","Text":"We also know that as we age,"},{"Start":"05:16.055 ","End":"05:18.500","Text":"our senses change in general,"},{"Start":"05:18.500 ","End":"05:22.330","Text":"but our taste senses are particularly vulnerable to this,"},{"Start":"05:22.330 ","End":"05:26.725","Text":"and after the age of 50, they decline precipitously."},{"Start":"05:26.725 ","End":"05:28.940","Text":"A child, for instance,"},{"Start":"05:28.940 ","End":"05:31.025","Text":"may find food to be too spicy,"},{"Start":"05:31.025 ","End":"05:34.610","Text":"but when he gets older and becomes an elderly person,"},{"Start":"05:34.610 ","End":"05:37.550","Text":"he may just find it on appetizing."},{"Start":"05:37.550 ","End":"05:40.610","Text":"Now, let\u0027s see how this gets to the brain."},{"Start":"05:40.610 ","End":"05:47.180","Text":"The olfactory neurons project from the olfactory epithelium to the olfactory bulb,"},{"Start":"05:47.180 ","End":"05:53.405","Text":"which is found above it in these thin, unmyelinated axons."},{"Start":"05:53.405 ","End":"05:58.415","Text":"Then there are other structures called the glomeruli."},{"Start":"05:58.415 ","End":"06:04.670","Text":"Glomerulus is one of them which then connect to the mitral cells."},{"Start":"06:04.670 ","End":"06:10.370","Text":"Each of these are specific to a particular odorant that is,"},{"Start":"06:10.370 ","End":"06:14.630","Text":"the receptors then will be specific to a particular odorants."},{"Start":"06:14.630 ","End":"06:21.080","Text":"From the glomeruli, the olfactory signals traveled by other cells called mitral cells,"},{"Start":"06:21.080 ","End":"06:23.780","Text":"other nerves to the olfactory cortex,"},{"Start":"06:23.780 ","End":"06:28.535","Text":"and then to the frontal cortex and the thalamus."},{"Start":"06:28.535 ","End":"06:32.390","Text":"All of this then is sensed in the brain,"},{"Start":"06:32.390 ","End":"06:36.875","Text":"as we said, in this gustatory cortex."},{"Start":"06:36.875 ","End":"06:44.770","Text":"It\u0027s the area that processes all this information and give us the feeling of taste."},{"Start":"06:44.770 ","End":"06:50.360","Text":"The taste neurons project taste cells from the tongue, esophagus,"},{"Start":"06:50.360 ","End":"06:57.230","Text":"and palate to the medulla in the brainstem and then to the thalamus,"},{"Start":"06:57.230 ","End":"07:01.070","Text":"and then to the gustatory cortex."},{"Start":"07:01.070 ","End":"07:04.505","Text":"Information from different regions of the tongue is"},{"Start":"07:04.505 ","End":"07:08.315","Text":"segregated in the medulla and thalamus and cortex,"},{"Start":"07:08.315 ","End":"07:10.265","Text":"but it\u0027s then processed."},{"Start":"07:10.265 ","End":"07:17.075","Text":"This very complicated system of different receptors"},{"Start":"07:17.075 ","End":"07:26.070","Text":"are then integrated in the brain in a rather complex way to give us a sense of flavor."}],"ID":30013}],"Thumbnail":null,"ID":284106},{"Name":"Hearing and Vestibular Sensation","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Introduction to Sound","Duration":"8m 1s","ChapterTopicVideoID":28520,"CourseChapterTopicPlaylistID":284107,"HasSubtitles":true,"ThumbnailPath":"https://www.proprep.uk/Images/Videos_Thumbnails/28520.jpeg","UploadDate":"2022-02-09T10:13:19.1600000","DurationForVideoObject":"PT8M1S","Description":null,"MetaTitle":"Introduction to Sound: Video + Workbook | Proprep","MetaDescription":"The Sensory System - Hearing and Vestibular Sensation. Watch the video made by an expert in the field. Download the workbook and maximize your learning.","Canonical":"https://www.proprep.uk/general-modules/all/introduction-to-biology/the-sensory-system/hearing-and-vestibular-sensation/vid30018","VideoComments":[],"Subtitles":[{"Start":"00:00.740 ","End":"00:04.140","Text":"I\u0027m glad that you\u0027ve returned."},{"Start":"00:04.140 ","End":"00:09.300","Text":"We\u0027re now going to continue our discussion of various sensations."},{"Start":"00:09.300 ","End":"00:17.175","Text":"When we\u0027re going to be concentrating on hearing as well as vestibular sensation."},{"Start":"00:17.175 ","End":"00:20.880","Text":"Vestibular sensation is going to have to do with how we"},{"Start":"00:20.880 ","End":"00:25.620","Text":"feel in space like when we move our heads and things of that sort."},{"Start":"00:25.620 ","End":"00:29.295","Text":"The first thing we\u0027re going to be doing is talking about hearing."},{"Start":"00:29.295 ","End":"00:32.565","Text":"Yes and about audition."},{"Start":"00:32.565 ","End":"00:36.095","Text":"Audio yes, is something that has to do with sounds,"},{"Start":"00:36.095 ","End":"00:42.455","Text":"and that\u0027s the sense by which noises and tones are received as stimuli."},{"Start":"00:42.455 ","End":"00:44.750","Text":"We hear things through the air."},{"Start":"00:44.750 ","End":"00:46.640","Text":"Now how is that work?"},{"Start":"00:46.640 ","End":"00:53.220","Text":"Well, we\u0027re going to study that in the continuation of this video."},{"Start":"00:53.220 ","End":"01:01.490","Text":"This audition or hearing things enables an organism basically to do two things."},{"Start":"01:01.490 ","End":"01:05.750","Text":"One is to communicate with the surroundings"},{"Start":"01:05.750 ","End":"01:10.520","Text":"by detecting and receiving information about the surroundings."},{"Start":"01:10.520 ","End":"01:12.560","Text":"You might hear, for instance,"},{"Start":"01:12.560 ","End":"01:14.300","Text":"another bird that it\u0027s singing,"},{"Start":"01:14.300 ","End":"01:18.485","Text":"and it may also hear other organisms,"},{"Start":"01:18.485 ","End":"01:22.280","Text":"either the same kind or different kinds that are doing something."},{"Start":"01:22.280 ","End":"01:27.125","Text":"These could have implications for territorial protection,"},{"Start":"01:27.125 ","End":"01:30.215","Text":"for mating, and things of that sort."},{"Start":"01:30.215 ","End":"01:33.195","Text":"Now, what is sound?"},{"Start":"01:33.195 ","End":"01:37.940","Text":"We know that there is air and they\u0027re molecules that are in the air,"},{"Start":"01:37.940 ","End":"01:41.450","Text":"and we also know that when we make a noise,"},{"Start":"01:41.450 ","End":"01:49.235","Text":"we push that air and we create waves that go through that air."},{"Start":"01:49.235 ","End":"01:56.060","Text":"Here you can see that very clearly as this plane passes through the sound barrier,"},{"Start":"01:56.060 ","End":"02:02.030","Text":"something happens that makes the wave that it\u0027s causing in the air change."},{"Start":"02:02.030 ","End":"02:03.680","Text":"That\u0027s what you\u0027re seeing over here."},{"Start":"02:03.680 ","End":"02:08.900","Text":"But the sound waves are mechanical pressure waves that move through a medium."},{"Start":"02:08.900 ","End":"02:11.780","Text":"In this case, it\u0027s the air and sometimes there\u0027s"},{"Start":"02:11.780 ","End":"02:15.320","Text":"sound through water like animals that are in the ocean."},{"Start":"02:15.320 ","End":"02:18.620","Text":"Now the speed with which the sound moves"},{"Start":"02:18.620 ","End":"02:21.590","Text":"is dependent on a number of things, is dependent,"},{"Start":"02:21.590 ","End":"02:23.420","Text":"of course, on how dense the air is,"},{"Start":"02:23.420 ","End":"02:27.725","Text":"and that changes whether we\u0027re at sea level or at higher elevations."},{"Start":"02:27.725 ","End":"02:30.515","Text":"It has to do with the temperature of the air."},{"Start":"02:30.515 ","End":"02:34.980","Text":"It has to do with of course,"},{"Start":"02:34.980 ","End":"02:39.495","Text":"how dense the air is, as I just said."},{"Start":"02:39.495 ","End":"02:41.780","Text":"That has to do with whether it\u0027s a sea level."},{"Start":"02:41.780 ","End":"02:44.540","Text":"I meant to give you an idea of how fast things are moving,"},{"Start":"02:44.540 ","End":"02:49.759","Text":"they generally at sea level and at 20 degrees Celsius temperature,"},{"Start":"02:49.759 ","End":"02:56.280","Text":"the speed of sound is about 343 meters per second."},{"Start":"02:56.290 ","End":"02:59.299","Text":"That\u0027s the issue of sound."},{"Start":"02:59.299 ","End":"03:03.695","Text":"We\u0027re going to return in a while to the vestibular system,"},{"Start":"03:03.695 ","End":"03:07.715","Text":"which detects not the sounds that are made,"},{"Start":"03:07.715 ","End":"03:10.010","Text":"but it detects the animal\u0027s movement."},{"Start":"03:10.010 ","End":"03:13.250","Text":"The reason that we put these two things together,"},{"Start":"03:13.250 ","End":"03:17.810","Text":"the detection of sound and the detection of movement of the animal is"},{"Start":"03:17.810 ","End":"03:22.410","Text":"that both of them work in a similar way as we\u0027ll see later."},{"Start":"03:22.410 ","End":"03:25.460","Text":"The vestibular system is going to have to"},{"Start":"03:25.460 ","End":"03:28.730","Text":"do with the detection of linear and angular acceleration."},{"Start":"03:28.730 ","End":"03:32.270","Text":"That is balance, really how the animal"},{"Start":"03:32.270 ","End":"03:38.149","Text":"can tell where it is vis-a-vis other things as it moves."},{"Start":"03:38.149 ","End":"03:40.250","Text":"These things are related one to another,"},{"Start":"03:40.250 ","End":"03:44.525","Text":"both because of the way they operate as we\u0027ll see as I said."},{"Start":"03:44.525 ","End":"03:45.980","Text":"In addition to that,"},{"Start":"03:45.980 ","End":"03:51.150","Text":"they\u0027re both associated in the ear."},{"Start":"03:51.150 ","End":"03:57.110","Text":"How do we measure sound and what are the different variables that sound has?"},{"Start":"03:57.110 ","End":"03:58.940","Text":"First of all, the, of course, there\u0027s the frequency,"},{"Start":"03:58.940 ","End":"04:01.250","Text":"whether it\u0027s a low pitch or a high pitch."},{"Start":"04:01.250 ","End":"04:04.850","Text":"That\u0027s the number of waves per unit time."},{"Start":"04:04.850 ","End":"04:06.890","Text":"You might have a low frequency."},{"Start":"04:06.890 ","End":"04:10.340","Text":"This would be the wave as a function of time,"},{"Start":"04:10.340 ","End":"04:12.290","Text":"which is right to left here."},{"Start":"04:12.290 ","End":"04:15.200","Text":"This would be a low frequency relative to"},{"Start":"04:15.200 ","End":"04:19.015","Text":"a higher frequency that we can see over here in the right."},{"Start":"04:19.015 ","End":"04:22.085","Text":"Of course we have to give these things units."},{"Start":"04:22.085 ","End":"04:25.180","Text":"Usually they\u0027re measured in how many cycles?"},{"Start":"04:25.180 ","End":"04:28.810","Text":"How many times you get from the same place on the wave,"},{"Start":"04:28.810 ","End":"04:30.850","Text":"say the bottom part here to the bottom part there."},{"Start":"04:30.850 ","End":"04:32.935","Text":"How many times that happens per second?"},{"Start":"04:32.935 ","End":"04:36.025","Text":"We measure that in units that are called hertz."},{"Start":"04:36.025 ","End":"04:39.055","Text":"The greater the number of hertz,"},{"Start":"04:39.055 ","End":"04:41.440","Text":"the greater number of cycles per second,"},{"Start":"04:41.440 ","End":"04:44.440","Text":"the higher the pitch is going to sound."},{"Start":"04:44.440 ","End":"04:48.580","Text":"Now humans are able to hear"},{"Start":"04:48.580 ","End":"04:55.690","Text":"only a limited number of different pitches from about 20 hertz to 20,000 hertz."},{"Start":"04:55.690 ","End":"04:59.080","Text":"On the other hand, other animals can"},{"Start":"04:59.080 ","End":"05:05.020","Text":"hear lot of pitches that can be either lower than that,"},{"Start":"05:05.020 ","End":"05:08.055","Text":"that are called infrasounds or higher"},{"Start":"05:08.055 ","End":"05:11.615","Text":"than where the humans here that we call ultrasounds."},{"Start":"05:11.615 ","End":"05:16.580","Text":"You can see, for instance, that dogs and cats can hear higher frequencies than we can."},{"Start":"05:16.580 ","End":"05:18.050","Text":"Dolphins and bats, of course,"},{"Start":"05:18.050 ","End":"05:20.119","Text":"here at much higher frequencies."},{"Start":"05:20.119 ","End":"05:23.180","Text":"Whereas larger animals, some of them,"},{"Start":"05:23.180 ","End":"05:25.430","Text":"like elephants, for instance,"},{"Start":"05:25.430 ","End":"05:29.105","Text":"can hear much lower pitches than we can."},{"Start":"05:29.105 ","End":"05:34.325","Text":"Whales also make very low pitched sounds."},{"Start":"05:34.325 ","End":"05:41.135","Text":"In other words, they have a very low frequency in the sounds that they emit."},{"Start":"05:41.135 ","End":"05:43.610","Text":"Now in addition to the frequency,"},{"Start":"05:43.610 ","End":"05:46.985","Text":"there is also a measure of how loud things are."},{"Start":"05:46.985 ","End":"05:49.635","Text":"We call that the amplitude."},{"Start":"05:49.635 ","End":"05:52.430","Text":"In other words, how high is this peak?"},{"Start":"05:52.430 ","End":"05:54.184","Text":"Not talking about the frequency,"},{"Start":"05:54.184 ","End":"05:55.640","Text":"we\u0027re talking about the amplitude."},{"Start":"05:55.640 ","End":"05:57.005","Text":"That\u0027s how loud it is."},{"Start":"05:57.005 ","End":"06:05.925","Text":"This mouse is making a soft quiet sound and the lion is making a much louder sound."},{"Start":"06:05.925 ","End":"06:08.970","Text":"Its amplitude is much higher."},{"Start":"06:08.970 ","End":"06:11.900","Text":"Of course, we know that there are all sounds in"},{"Start":"06:11.900 ","End":"06:17.360","Text":"our environments and each of them has a typical intensity."},{"Start":"06:17.360 ","End":"06:20.380","Text":"For instance, we\u0027re breathing, we\u0027re quite quiet."},{"Start":"06:20.380 ","End":"06:22.369","Text":"When we hear fireworks,"},{"Start":"06:22.369 ","End":"06:27.785","Text":"it\u0027s quite a lot of noise or a jet plane moving by police siren and so on."},{"Start":"06:27.785 ","End":"06:31.840","Text":"This is measured then in decibels."},{"Start":"06:31.840 ","End":"06:36.950","Text":"Decibels, sometimes it\u0027s abbreviated small dB."},{"Start":"06:36.950 ","End":"06:39.440","Text":"You could see when we\u0027re chatting like we are at the moment,"},{"Start":"06:39.440 ","End":"06:44.560","Text":"we\u0027re roughly at 60 decibels to give you an idea."},{"Start":"06:44.560 ","End":"06:47.510","Text":"Of course, the human ear can only"},{"Start":"06:47.510 ","End":"06:52.295","Text":"hear within that particular frequency range, as we mentioned."},{"Start":"06:52.295 ","End":"06:59.235","Text":"But it also can only hear a certain number of decibels or a certain spread of decimals."},{"Start":"06:59.235 ","End":"07:01.530","Text":"Between 0 and about 120,"},{"Start":"07:01.530 ","End":"07:05.285","Text":"130 in the mid frequency range,"},{"Start":"07:05.285 ","End":"07:07.640","Text":"but roughly 1 to 2 kilohertz."},{"Start":"07:07.640 ","End":"07:10.130","Text":"For lower and higher frequencies,"},{"Start":"07:10.130 ","End":"07:14.340","Text":"the dynamic ranges narrowed even further."},{"Start":"07:14.720 ","End":"07:21.580","Text":"Let\u0027s say one more thing about the lower frequencies and the amplitude."},{"Start":"07:21.580 ","End":"07:24.145","Text":"In whales, for instance,"},{"Start":"07:24.145 ","End":"07:27.730","Text":"it can have a huge amplitude as well as having"},{"Start":"07:27.730 ","End":"07:33.580","Text":"very low frequency in which they can emit sounds,"},{"Start":"07:33.580 ","End":"07:39.190","Text":"and therefore, they can be heard very far away."},{"Start":"07:39.190 ","End":"07:44.230","Text":"You can see via vocalizations up to about a 188 decibels can be heard as"},{"Start":"07:44.230 ","End":"07:49.495","Text":"far away as 160 kilometers through the water."},{"Start":"07:49.495 ","End":"07:53.215","Text":"This is the loudest animal, the blue whale."},{"Start":"07:53.215 ","End":"07:54.490","Text":"In the next video,"},{"Start":"07:54.490 ","End":"08:00.110","Text":"we\u0027ll discuss how these sounds are heard in the human ear."}],"ID":30018},{"Watched":false,"Name":"Sound Perception in the Outer and Middle Ear","Duration":"8m 2s","ChapterTopicVideoID":28517,"CourseChapterTopicPlaylistID":284107,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.770","Text":"Let\u0027s continue to discuss sound and see what happens"},{"Start":"00:04.770 ","End":"00:10.905","Text":"when it encounters the human ear or any other ear for that matter."},{"Start":"00:10.905 ","End":"00:13.040","Text":"As you know, many animals,"},{"Start":"00:13.040 ","End":"00:15.090","Text":"most animals in fact,"},{"Start":"00:15.090 ","End":"00:20.025","Text":"have some outer appendage on the outside of their head,"},{"Start":"00:20.025 ","End":"00:24.225","Text":"which is called an auricle or a pinna."},{"Start":"00:24.225 ","End":"00:27.750","Text":"It\u0027s Latin for wing or fin."},{"Start":"00:27.750 ","End":"00:32.745","Text":"That\u0027s the visible portion of the external ear that we can see."},{"Start":"00:32.745 ","End":"00:34.590","Text":"Of course, what does it do?"},{"Start":"00:34.590 ","End":"00:40.730","Text":"It collects sound waves and then channels them into the auditory canal."},{"Start":"00:40.730 ","End":"00:42.350","Text":"The sounds can come,"},{"Start":"00:42.350 ","End":"00:45.290","Text":"let\u0027s say, from different directions,"},{"Start":"00:45.290 ","End":"00:50.925","Text":"but they\u0027re all channeled into the inner ear."},{"Start":"00:50.925 ","End":"00:54.560","Text":"To begin with, we\u0027ll begin to amplify the signal."},{"Start":"00:54.560 ","End":"00:55.760","Text":"You know, for instance,"},{"Start":"00:55.760 ","End":"01:00.740","Text":"that if you cup your hand around your ear,"},{"Start":"01:00.740 ","End":"01:06.320","Text":"you can make things sound even a little bit louder because then your hand is"},{"Start":"01:06.320 ","End":"01:13.460","Text":"channeling some more of the vibrations into this auditory canal that goes into your head."},{"Start":"01:13.460 ","End":"01:16.465","Text":"The sound travels through this auditory canal."},{"Start":"01:16.465 ","End":"01:19.915","Text":"The first thing that it encounters is your eardrum,"},{"Start":"01:19.915 ","End":"01:24.300","Text":"which is called the tympanic membrane."},{"Start":"01:24.300 ","End":"01:27.515","Text":"This membrane then begins to move."},{"Start":"01:27.515 ","End":"01:32.300","Text":"That membrane we will see will be contacted by"},{"Start":"01:32.300 ","End":"01:39.050","Text":"a few bones that will move things further inside the inner ear."},{"Start":"01:39.050 ","End":"01:42.485","Text":"Interestingly, pretty much all mammals,"},{"Start":"01:42.485 ","End":"01:43.775","Text":"there are few exceptions,"},{"Start":"01:43.775 ","End":"01:47.120","Text":"have this pinna on their outside."},{"Start":"01:47.120 ","End":"01:48.800","Text":"There are some animals, for instance,"},{"Start":"01:48.800 ","End":"01:50.150","Text":"that live in the water,"},{"Start":"01:50.150 ","End":"01:56.155","Text":"where this pinna will be very small so that they can swim more efficiently."},{"Start":"01:56.155 ","End":"01:58.830","Text":"Let\u0027s now look back into the ear."},{"Start":"01:58.830 ","End":"02:01.695","Text":"First, we have the middle ear."},{"Start":"02:01.695 ","End":"02:05.475","Text":"Beyond this tympanic membrane that you can see here,"},{"Start":"02:05.475 ","End":"02:09.485","Text":"so this is an enlargement of what you see down here,"},{"Start":"02:09.485 ","End":"02:15.950","Text":"there are 3 bones that are called ossicle bones: malleus,"},{"Start":"02:15.950 ","End":"02:18.020","Text":"incus, and stapes."},{"Start":"02:18.020 ","End":"02:20.930","Text":"Here you can see them. The malleus,"},{"Start":"02:20.930 ","End":"02:24.080","Text":"the incus, and the stapes."},{"Start":"02:24.080 ","End":"02:27.095","Text":"These are 3 different bones that are connected to each other."},{"Start":"02:27.095 ","End":"02:29.840","Text":"The malleus is connected to the tympanic membrane."},{"Start":"02:29.840 ","End":"02:31.130","Text":"As you can see here,"},{"Start":"02:31.130 ","End":"02:35.600","Text":"what happens is that when the tympanic membrane moves,"},{"Start":"02:35.600 ","End":"02:43.220","Text":"it then moves these bones and it then transfers mechanical energy then from the eardrum,"},{"Start":"02:43.220 ","End":"02:44.855","Text":"from the tympanum,"},{"Start":"02:44.855 ","End":"02:48.710","Text":"to an area called the oval window,"},{"Start":"02:48.710 ","End":"02:51.245","Text":"which is in this middle ear."},{"Start":"02:51.245 ","End":"02:54.635","Text":"It\u0027s the exterior boundary of the inner ear,"},{"Start":"02:54.635 ","End":"02:57.180","Text":"which is over here on the right."},{"Start":"02:57.180 ","End":"03:04.880","Text":"These 3 bones also serve as sound amplifiers because if this moves just a little bit,"},{"Start":"03:04.880 ","End":"03:07.175","Text":"it turns out with this geometry,"},{"Start":"03:07.175 ","End":"03:10.615","Text":"then the stapes moves a lot."},{"Start":"03:10.615 ","End":"03:13.095","Text":"It\u0027s an amplifier."},{"Start":"03:13.095 ","End":"03:15.240","Text":"The 3 ossicles,"},{"Start":"03:15.240 ","End":"03:16.415","Text":"these 3 bones,"},{"Start":"03:16.415 ","End":"03:18.260","Text":"are unique to mammals."},{"Start":"03:18.260 ","End":"03:21.200","Text":"It turns out that other animals like frogs,"},{"Start":"03:21.200 ","End":"03:24.680","Text":"reptiles, and birds have only the stapes."},{"Start":"03:24.680 ","End":"03:28.250","Text":"That\u0027s an interesting evolutionary effect."},{"Start":"03:28.250 ","End":"03:32.035","Text":"Now let\u0027s look what happens in the inner ear."},{"Start":"03:32.035 ","End":"03:36.080","Text":"On the inner ear, we have a structure that looks"},{"Start":"03:36.080 ","End":"03:40.760","Text":"something like this and we\u0027ll expand on it considerably further."},{"Start":"03:40.760 ","End":"03:45.680","Text":"You can see that there is this area called the cochlea,"},{"Start":"03:45.680 ","End":"03:51.905","Text":"which is a snail-looking structure"},{"Start":"03:51.905 ","End":"03:56.675","Text":"and we\u0027ll see that it\u0027s a long channel which goes into a circle,"},{"Start":"03:56.675 ","End":"04:01.610","Text":"and the vibrations are transferred then from this oval window into the fluid,"},{"Start":"04:01.610 ","End":"04:04.970","Text":"which is found inside the cochlea."},{"Start":"04:04.970 ","End":"04:08.485","Text":"That\u0027s movement then creates pressure waves in the fluid."},{"Start":"04:08.485 ","End":"04:10.850","Text":"The fluid there is called perilymph,"},{"Start":"04:10.850 ","End":"04:13.070","Text":"that is inside the cochlea,"},{"Start":"04:13.070 ","End":"04:18.269","Text":"and that\u0027s going to be sensed by something called the organ"},{"Start":"04:18.269 ","End":"04:24.360","Text":"of Corti which is inside the cochlea."},{"Start":"04:24.360 ","End":"04:29.810","Text":"The organ of Corti is going to transduce the mechanical energy,"},{"Start":"04:29.810 ","End":"04:31.745","Text":"that was the sounds,"},{"Start":"04:31.745 ","End":"04:34.910","Text":"into an electrical signal in the nerves."},{"Start":"04:34.910 ","End":"04:39.260","Text":"There\u0027s this nerve, the vestibulocochlear nerve is going to"},{"Start":"04:39.260 ","End":"04:44.285","Text":"go into the brain that transmits the sound signal."},{"Start":"04:44.285 ","End":"04:48.520","Text":"Let\u0027s look at this even more closely."},{"Start":"04:48.520 ","End":"04:51.215","Text":"Inside the cochlea,"},{"Start":"04:51.215 ","End":"04:53.570","Text":"we have here it\u0027s straightened out this,"},{"Start":"04:53.570 ","End":"04:55.895","Text":"in this drawing just for the sake of illustration."},{"Start":"04:55.895 ","End":"05:00.364","Text":"As we said before, it goes in a spiral."},{"Start":"05:00.364 ","End":"05:05.959","Text":"But all along inside the cochlear duct,"},{"Start":"05:05.959 ","End":"05:13.760","Text":"there are these organs of Corti that are going to pick up the different sounds."},{"Start":"05:13.760 ","End":"05:21.770","Text":"Interestingly, each region of the basilar membrane,"},{"Start":"05:21.770 ","End":"05:23.765","Text":"which is inside the cochlea,"},{"Start":"05:23.765 ","End":"05:27.305","Text":"is tuned to a particular vibration frequency."},{"Start":"05:27.305 ","End":"05:32.650","Text":"Different places will pick up different frequencies."},{"Start":"05:32.650 ","End":"05:35.560","Text":"We\u0027ll come back to that in a little bit."},{"Start":"05:35.560 ","End":"05:40.610","Text":"The cochlea detects different wave frequencies at different regions of the membrane."},{"Start":"05:40.610 ","End":"05:44.240","Text":"That\u0027s going to be the way that we can tell"},{"Start":"05:44.240 ","End":"05:48.480","Text":"the difference between a very high pitch and a low pitch"},{"Start":"05:48.480 ","End":"05:52.640","Text":"because the stimulation is different in the different places"},{"Start":"05:52.640 ","End":"05:57.920","Text":"inside the cochlea along the basal membrane."},{"Start":"05:57.920 ","End":"06:02.753","Text":"When the sound waves in the cochlear fluid contact this basilar membrane,"},{"Start":"06:02.753 ","End":"06:07.790","Text":"it flexes that membrane in a wave-like fashion and"},{"Start":"06:07.790 ","End":"06:13.325","Text":"that is what\u0027s going to be picked up by mechanoreceptors,"},{"Start":"06:13.325 ","End":"06:19.305","Text":"little hair cells that have what are called short stereocilia."},{"Start":"06:19.305 ","End":"06:23.610","Text":"At the very tip of cells,"},{"Start":"06:23.610 ","End":"06:29.255","Text":"we will find these small hair, stereocilia,"},{"Start":"06:29.255 ","End":"06:33.290","Text":"that are above the basilar membrane and they"},{"Start":"06:33.290 ","End":"06:38.390","Text":"contact another membrane called the tectorial membrane,"},{"Start":"06:38.390 ","End":"06:39.950","Text":"which is just above."},{"Start":"06:39.950 ","End":"06:44.240","Text":"They\u0027re going to be small hairs that you can\u0027t quite see in this picture,"},{"Start":"06:44.240 ","End":"06:45.665","Text":"but they are here."},{"Start":"06:45.665 ","End":"06:48.140","Text":"Here on the right side,"},{"Start":"06:48.140 ","End":"06:51.290","Text":"we have an expansion of what we have in here,"},{"Start":"06:51.290 ","End":"06:54.575","Text":"which is an expansion of the picture that we saw before."},{"Start":"06:54.575 ","End":"06:57.245","Text":"Notice that it\u0027s inside a bone."},{"Start":"06:57.245 ","End":"07:04.020","Text":"Here\u0027s a piece of the vestibulocochlear nerve that we see here"},{"Start":"07:04.020 ","End":"07:11.145","Text":"again and each of them then goes to the organ of Corti,"},{"Start":"07:11.145 ","End":"07:13.950","Text":"which contains these cells."},{"Start":"07:13.950 ","End":"07:20.620","Text":"The hairs are bent by the vibrations, the stereocilia,"},{"Start":"07:20.620 ","End":"07:27.560","Text":"and that then opens gated channels that are in these nerves causing a depolarization,"},{"Start":"07:27.560 ","End":"07:30.770","Text":"and then you have a signal that\u0027s transmitted through"},{"Start":"07:30.770 ","End":"07:35.020","Text":"the nerves as we saw in earlier videos."},{"Start":"07:35.020 ","End":"07:37.620","Text":"The intensity of the sound,"},{"Start":"07:37.620 ","End":"07:39.430","Text":"in other words, how loud it is,"},{"Start":"07:39.430 ","End":"07:44.450","Text":"is determined by how many different hair cells at a particular location are stimulated."},{"Start":"07:44.450 ","End":"07:46.069","Text":"Of course, if things are loud,"},{"Start":"07:46.069 ","End":"07:50.195","Text":"then we\u0027re going to have more stimulation."},{"Start":"07:50.195 ","End":"07:51.710","Text":"In the next video,"},{"Start":"07:51.710 ","End":"08:00.870","Text":"we\u0027ll look more closely at what\u0027s going on inside the organ of Corti."}],"ID":30019},{"Watched":false,"Name":"Sound Waves Transmitted to Nerve Impulses","Duration":"5m 49s","ChapterTopicVideoID":28518,"CourseChapterTopicPlaylistID":284107,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.830 ","End":"00:06.795","Text":"Let\u0027s continue our discussion of the organ of corti."},{"Start":"00:06.795 ","End":"00:09.045","Text":"Let\u0027s continue our discussion."},{"Start":"00:09.045 ","End":"00:12.495","Text":"We were talking about the hair cells which are"},{"Start":"00:12.495 ","End":"00:19.365","Text":"inside the organ of corti and that are going to be sensing the sound."},{"Start":"00:19.365 ","End":"00:27.510","Text":"Here we have again those cells and they touch this other membrane above,"},{"Start":"00:27.510 ","End":"00:29.415","Text":"as we mentioned earlier."},{"Start":"00:29.415 ","End":"00:33.690","Text":"Here now you can see those outer hair cells."},{"Start":"00:33.690 ","End":"00:37.110","Text":"This is an expansion of what we have above."},{"Start":"00:37.110 ","End":"00:45.895","Text":"This is the upper tectorial membrane and the lower basilar membrane."},{"Start":"00:45.895 ","End":"00:49.820","Text":"Between the tool you can see there are these cells that contain"},{"Start":"00:49.820 ","End":"00:53.615","Text":"the hairs that are going to sense the sounds."},{"Start":"00:53.615 ","End":"00:55.640","Text":"They are arranged on the basilar membrane,"},{"Start":"00:55.640 ","End":"00:57.920","Text":"as we said, in an orderly way."},{"Start":"00:57.920 ","End":"01:04.055","Text":"Each of these detects different frequencies of sounds,"},{"Start":"01:04.055 ","End":"01:08.195","Text":"then the range is really quite amazing."},{"Start":"01:08.195 ","End":"01:16.295","Text":"The difference in response frequency between adjacent inner hair cells is about 0.2%."},{"Start":"01:16.295 ","End":"01:19.460","Text":"But adjacent cells can respond a little bit"},{"Start":"01:19.460 ","End":"01:23.690","Text":"differently or respond to small changes in frequency."},{"Start":"01:23.690 ","End":"01:26.500","Text":"To give you an idea about how much that is,"},{"Start":"01:26.500 ","End":"01:28.315","Text":"piano strings, for instance,"},{"Start":"01:28.315 ","End":"01:34.040","Text":"that are adjacent like a halftone on a piano are 6%."},{"Start":"01:35.190 ","End":"01:38.590","Text":"This is 5 in 1%."},{"Start":"01:38.590 ","End":"01:45.370","Text":"It\u0027s 30 fold more sensitive than the difference between piano strings."},{"Start":"01:45.370 ","End":"01:47.375","Text":"That\u0027s pretty good."},{"Start":"01:47.375 ","End":"01:49.570","Text":"As we mentioned earlier,"},{"Start":"01:49.570 ","End":"01:53.920","Text":"the position of these cells along"},{"Start":"01:53.920 ","End":"02:03.295","Text":"the cochlea channel makes a difference in which frequencies are heard."},{"Start":"02:03.295 ","End":"02:07.670","Text":"There\u0027s a place theory about pitch perception,"},{"Start":"02:07.670 ","End":"02:10.925","Text":"and it states that sound perception depends on where"},{"Start":"02:10.925 ","End":"02:15.875","Text":"each component frequency produces vibrations along the basilar membrane."},{"Start":"02:15.875 ","End":"02:23.390","Text":"Inside the cochlea, there is this fluid and the sound that goes"},{"Start":"02:23.390 ","End":"02:26.990","Text":"in then will stimulate the hairs in"},{"Start":"02:26.990 ","End":"02:30.905","Text":"different places depending on the frequency of the sound."},{"Start":"02:30.905 ","End":"02:33.755","Text":"The higher frequency sounds vibrates,"},{"Start":"02:33.755 ","End":"02:41.959","Text":"basilar membrane near the entrance and the lower pitches will be closer to the apex."},{"Start":"02:41.959 ","End":"02:44.630","Text":"The lower pitches closer the apex."},{"Start":"02:44.630 ","End":"02:49.500","Text":"That\u0027s the further way for the part here you can see the apex."},{"Start":"02:49.500 ","End":"02:58.775","Text":"The neuronal signal that is generated then actually it can be split into 2."},{"Start":"02:58.775 ","End":"03:03.065","Text":"There\u0027s what\u0027s called the primary lemniscal pathway."},{"Start":"03:03.065 ","End":"03:04.430","Text":"That\u0027s the main pathway,"},{"Start":"03:04.430 ","End":"03:06.960","Text":"that\u0027s what we hear mostly."},{"Start":"03:07.390 ","End":"03:12.110","Text":"It carries the messages from the cochlea that we just"},{"Start":"03:12.110 ","End":"03:16.790","Text":"described to the auditory complex that\u0027s in our brain,"},{"Start":"03:16.790 ","End":"03:19.440","Text":"which is in the temporal lobe."},{"Start":"03:19.440 ","End":"03:24.695","Text":"As you can see, it goes through the base of"},{"Start":"03:24.695 ","End":"03:30.590","Text":"the brain and it stimulates the auditory cortex, as we said."},{"Start":"03:30.590 ","End":"03:36.095","Text":"In addition to that, there is another pathway, non lemniscal pathway."},{"Start":"03:36.095 ","End":"03:41.705","Text":"That is something that\u0027s a little bit less primary, it\u0027s more minor,"},{"Start":"03:41.705 ","End":"03:46.820","Text":"but it mediates all sorts of unconscious perceptions such as attention,"},{"Start":"03:46.820 ","End":"03:49.490","Text":"emotional response, auditory reflexes and things like that."},{"Start":"03:49.490 ","End":"03:52.880","Text":"Like you\u0027ll hear a very loud sound and you may"},{"Start":"03:52.880 ","End":"03:57.665","Text":"respond to it before you even realize what you\u0027ve heard."},{"Start":"03:57.665 ","End":"04:04.865","Text":"The auditory cortex in the brain then consists itself of"},{"Start":"04:04.865 ","End":"04:12.615","Text":"a primary auditory cortex and a secondary auditory cortex."},{"Start":"04:12.615 ","End":"04:17.235","Text":"These different areas respond to"},{"Start":"04:17.235 ","End":"04:23.495","Text":"different places that are in the cochlea,"},{"Start":"04:23.495 ","End":"04:25.760","Text":"different regions of the cochlea."},{"Start":"04:25.760 ","End":"04:29.435","Text":"If you remember, those different regions have to do with picking up"},{"Start":"04:29.435 ","End":"04:35.340","Text":"different frequencies of sounds and they are arranged in the brain even."},{"Start":"04:35.900 ","End":"04:42.305","Text":"That helps us then distinguish which frequencies we hear."},{"Start":"04:42.305 ","End":"04:44.915","Text":"This is similar to the cochlea,"},{"Start":"04:44.915 ","End":"04:50.465","Text":"the primary auditory complex is organized in what\u0027s called tonotopy,"},{"Start":"04:50.465 ","End":"04:52.325","Text":"in a tonotopy fashion."},{"Start":"04:52.325 ","End":"04:57.665","Text":"That is the neurons at 1 end of the auditory cortex respond best to."},{"Start":"04:57.665 ","End":"05:04.190","Text":"Low frequencies, and the neurons at the other end responds best to the high frequencies."},{"Start":"05:04.190 ","End":"05:05.705","Text":"In addition to that,"},{"Start":"05:05.705 ","End":"05:08.330","Text":"there is a sharpening of the signal."},{"Start":"05:08.330 ","End":"05:12.870","Text":"That\u0027s the amplitude has"},{"Start":"05:12.870 ","End":"05:20.885","Text":"to reach a certain level in order for these hairs to fire the nerves."},{"Start":"05:20.885 ","End":"05:29.030","Text":"Even though there might be some sound at the frequency surrounding the main frequency,"},{"Start":"05:29.030 ","End":"05:32.480","Text":"those may not get transmitted."},{"Start":"05:32.480 ","End":"05:37.955","Text":"Only the ones that are in the center of the large wave will be transmitted."},{"Start":"05:37.955 ","End":"05:42.420","Text":"This sharpens what\u0027s called the response curve of the ear,"},{"Start":"05:42.420 ","End":"05:50.040","Text":"and that scales the pitch resolution so we hear the pitch more clearly this way."}],"ID":30020},{"Watched":false,"Name":"Vestibular Sensations","Duration":"7m 5s","ChapterTopicVideoID":28519,"CourseChapterTopicPlaylistID":284107,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.740","Text":"Finally, let\u0027s end our discussion of hearing and"},{"Start":"00:04.740 ","End":"00:10.155","Text":"vestibular sensation by talking about the vestibular sensation."},{"Start":"00:10.155 ","End":"00:13.071","Text":"Vestibular means equilibrium,"},{"Start":"00:13.071 ","End":"00:16.710","Text":"and it has to do with whether we understand that we\u0027re standing up straight"},{"Start":"00:16.710 ","End":"00:21.720","Text":"and not moving or that we are moving in space."},{"Start":"00:21.720 ","End":"00:24.600","Text":"There\u0027s something called static equilibrium,"},{"Start":"00:24.600 ","End":"00:28.470","Text":"that is gravity which is detected through head position."},{"Start":"00:28.470 ","End":"00:30.360","Text":"Of course, if we suddenly move our head,"},{"Start":"00:30.360 ","End":"00:35.845","Text":"we feel something that has to do with this vestibular sensation."},{"Start":"00:35.845 ","End":"00:38.585","Text":"There\u0027s a dynamic equilibrium,"},{"Start":"00:38.585 ","End":"00:41.350","Text":"that\u0027s the angular acceleration or deceleration."},{"Start":"00:41.350 ","End":"00:43.370","Text":"If we\u0027re standing still,"},{"Start":"00:43.370 ","End":"00:44.990","Text":"that\u0027s the static equilibrium."},{"Start":"00:44.990 ","End":"00:47.840","Text":"If we\u0027re moving, it\u0027s the dynamic equilibrium,"},{"Start":"00:47.840 ","End":"00:51.950","Text":"and that we feel by some sort of dizziness"},{"Start":"00:51.950 ","End":"00:56.480","Text":"or anyhow we can feel it in our head when we move it,"},{"Start":"00:56.480 ","End":"00:58.445","Text":"and how does that work?"},{"Start":"00:58.445 ","End":"01:03.035","Text":"Well, it turns out that inside our inner ear,"},{"Start":"01:03.035 ","End":"01:07.320","Text":"we have an organ. Here\u0027s the cochlea."},{"Start":"01:07.320 ","End":"01:10.145","Text":"A little bit further inside the inner ear,"},{"Start":"01:10.145 ","End":"01:16.970","Text":"we have an organ which is designed to give us this vestibular information."},{"Start":"01:16.970 ","End":"01:19.670","Text":"In it are several parts."},{"Start":"01:19.670 ","End":"01:23.300","Text":"There\u0027s the utricle that you can see here."},{"Start":"01:23.300 ","End":"01:25.630","Text":"There\u0027s the saccule."},{"Start":"01:25.630 ","End":"01:32.300","Text":"There are 3 semicircular canals that are the anterior, posterior,"},{"Start":"01:32.300 ","End":"01:34.430","Text":"and lateral canals,"},{"Start":"01:34.430 ","End":"01:40.010","Text":"and altogether all of these make up what\u0027s called the vestibular labyrinth."},{"Start":"01:40.010 ","End":"01:42.310","Text":"We\u0027ll see in a minute how this works."},{"Start":"01:42.310 ","End":"01:47.765","Text":"Inside, we have also hair cells very similar to the hearing."},{"Start":"01:47.765 ","End":"01:51.740","Text":"We have the vestibular nerve that we saw earlier,"},{"Start":"01:51.740 ","End":"01:57.360","Text":"and we have various as we\u0027ll see, liquids,"},{"Start":"01:57.360 ","End":"02:02.450","Text":"and solids and ducts that are adjacent to these hairs that are going to be"},{"Start":"02:02.450 ","End":"02:08.505","Text":"determining whether liquid is moving one direction or the other."},{"Start":"02:08.505 ","End":"02:13.640","Text":"There are these hair cells in the utricle and in the saccule that are"},{"Start":"02:13.640 ","End":"02:18.815","Text":"projecting into this gelatinous material, this liquid material."},{"Start":"02:18.815 ","End":"02:23.180","Text":"There are the solids that I mentioned briefly that are called otoliths,"},{"Start":"02:23.180 ","End":"02:26.300","Text":"that are crystals that are embedded in the gel and they allow to"},{"Start":"02:26.300 ","End":"02:30.860","Text":"perceive the position relative to gravity or movement."},{"Start":"02:30.860 ","End":"02:32.660","Text":"When the head is tilted, of course,"},{"Start":"02:32.660 ","End":"02:34.940","Text":"the crystals will move as well,"},{"Start":"02:34.940 ","End":"02:37.985","Text":"but not at the same speed as your head,"},{"Start":"02:37.985 ","End":"02:43.760","Text":"and therefore the hairs will be bent one way or another."},{"Start":"02:43.760 ","End":"02:48.695","Text":"These stereocilia, just like the ones that we saw before,"},{"Start":"02:48.695 ","End":"02:52.445","Text":"that had to do with hearing are bent in a different direction."},{"Start":"02:52.445 ","End":"02:57.230","Text":"The bent stereocilia stimulate the neurons very much like"},{"Start":"02:57.230 ","End":"03:02.690","Text":"hearing that signaled to the brain something about the head position."},{"Start":"03:02.690 ","End":"03:08.185","Text":"There are these fluid filled semicircular ducts,"},{"Start":"03:08.185 ","End":"03:12.635","Text":"and we mentioned that they are these hairs at the end of them."},{"Start":"03:12.635 ","End":"03:15.860","Text":"These loops are set at"},{"Start":"03:15.860 ","End":"03:20.430","Text":"oblique angles one with respect to the other projecting in 3 different planes,"},{"Start":"03:20.430 ","End":"03:26.840","Text":"and that\u0027s going to give us the information about which direction we are moving."},{"Start":"03:26.840 ","End":"03:32.360","Text":"Each canal then contains this semicircular duct and"},{"Start":"03:32.360 ","End":"03:38.665","Text":"at the base of it is something called the crista ampullaris."},{"Start":"03:38.665 ","End":"03:46.115","Text":"Inside it, the crista ampullaris are where these hair cells are with these cilia,"},{"Start":"03:46.115 ","End":"03:49.535","Text":"and they\u0027re going to detect the movement of"},{"Start":"03:49.535 ","End":"03:55.090","Text":"the liquid that is embedded in what\u0027s called the cupula."},{"Start":"03:55.090 ","End":"03:59.960","Text":"The endolymph, this liquid that\u0027s in here this endolymph,"},{"Start":"03:59.960 ","End":"04:01.550","Text":"just provides the inertia,"},{"Start":"04:01.550 ","End":"04:03.890","Text":"so the sensory process will bend, of course,"},{"Start":"04:03.890 ","End":"04:06.540","Text":"in the opposite direction to where the head is moved."},{"Start":"04:06.540 ","End":"04:08.435","Text":"If you move your head to the right,"},{"Start":"04:08.435 ","End":"04:10.970","Text":"or in this case it\u0027s moving to the left."},{"Start":"04:10.970 ","End":"04:18.064","Text":"Then of course the cilia will move to the right and that will be translated by our brain."},{"Start":"04:18.064 ","End":"04:24.275","Text":"After the signals is transferred through this nerve into the brain,"},{"Start":"04:24.275 ","End":"04:28.720","Text":"it will be translated into our direction of movement."},{"Start":"04:28.720 ","End":"04:32.175","Text":"Let\u0027s see now what the brain does in more detail."},{"Start":"04:32.175 ","End":"04:37.425","Text":"The nerve cells of force are going to communicate into the brain,"},{"Start":"04:37.425 ","End":"04:40.925","Text":"and they communicate through bipolar neurons."},{"Start":"04:40.925 ","End":"04:43.640","Text":"Bipolar meaning they\u0027re going into different directions,"},{"Start":"04:43.640 ","End":"04:46.175","Text":"to the vestibular nuclei in the medulla."},{"Start":"04:46.175 ","End":"04:49.430","Text":"That nuclei when we talk about nuclei in the brain,"},{"Start":"04:49.430 ","End":"04:52.115","Text":"we\u0027re talking about collections of nerves."},{"Start":"04:52.115 ","End":"04:55.340","Text":"The vestibular nuclei that you see here are"},{"Start":"04:55.340 ","End":"04:59.090","Text":"connections of nerves that go both down and up."},{"Start":"04:59.090 ","End":"05:02.810","Text":"Yes, they go up when they ascend into"},{"Start":"05:02.810 ","End":"05:06.650","Text":"the thalamus and they go in the cerebellum of course,"},{"Start":"05:06.650 ","End":"05:09.560","Text":"and they go down when they project into"},{"Start":"05:09.560 ","End":"05:14.150","Text":"the spinal cord where we might have a quick movement."},{"Start":"05:14.150 ","End":"05:17.785","Text":"This generated by those nerves if we hear a loud sound."},{"Start":"05:17.785 ","End":"05:20.570","Text":"There are projections in the temporal cortex that"},{"Start":"05:20.570 ","End":"05:23.540","Text":"brain-stem the primary somatosensory cortex,"},{"Start":"05:23.540 ","End":"05:28.850","Text":"all of these things then process the information that we get both from"},{"Start":"05:28.850 ","End":"05:35.225","Text":"the hearing and from the vestibular sensation about what\u0027s happening around us."},{"Start":"05:35.225 ","End":"05:41.540","Text":"Finally, let\u0027s look briefly at what happens in animals that are not us."},{"Start":"05:41.540 ","End":"05:43.360","Text":"In fish, for instance."},{"Start":"05:43.360 ","End":"05:45.245","Text":"It turns out, for instance,"},{"Start":"05:45.245 ","End":"05:48.275","Text":"that fish don\u0027t have these complicated ears."},{"Start":"05:48.275 ","End":"05:53.500","Text":"They have these just a pair of inner ears that are near the brain."},{"Start":"05:53.500 ","End":"05:54.700","Text":"In addition to that,"},{"Start":"05:54.700 ","End":"05:56.500","Text":"they have something called a lateral line."},{"Start":"05:56.500 ","End":"05:58.720","Text":"If you look at a fish along the side of it,"},{"Start":"05:58.720 ","End":"06:00.610","Text":"there\u0027s this line,"},{"Start":"06:00.610 ","End":"06:02.440","Text":"and if we enlarge it,"},{"Start":"06:02.440 ","End":"06:04.960","Text":"and you can see here these are the scales."},{"Start":"06:04.960 ","End":"06:08.010","Text":"These tan lines are the scales,"},{"Start":"06:08.010 ","End":"06:14.115","Text":"and water can flow through this lateral line."},{"Start":"06:14.115 ","End":"06:15.430","Text":"There\u0027s a hole there."},{"Start":"06:15.430 ","End":"06:20.880","Text":"The water that flows there is going to move against something that\u0027s quite similar as"},{"Start":"06:20.880 ","End":"06:27.580","Text":"sensory hairs to what we saw in the vestibular ideas that are inside a human ear."},{"Start":"06:27.580 ","End":"06:32.910","Text":"That is going to be translated after these action potentials go to the brain."},{"Start":"06:32.910 ","End":"06:35.720","Text":"The fish are going to be translated into things that have to"},{"Start":"06:35.720 ","End":"06:39.110","Text":"do with movements around the fish."},{"Start":"06:39.110 ","End":"06:44.230","Text":"It\u0027s sensing things in the water around the fish."},{"Start":"06:44.230 ","End":"06:46.880","Text":"The lateral line system contains"},{"Start":"06:46.880 ","End":"06:50.300","Text":"these mechanoreceptors with hair cells"},{"Start":"06:50.300 ","End":"06:54.065","Text":"that are very similar as I said to what\u0027s happening in the ear."},{"Start":"06:54.065 ","End":"07:02.870","Text":"That response then to say a predator that might be coming from the side of the fish,"},{"Start":"07:02.870 ","End":"07:05.880","Text":"and causing it to move away."}],"ID":30021}],"Thumbnail":null,"ID":284107},{"Name":"The Visual System","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Light and the eye","Duration":"6m 54s","ChapterTopicVideoID":28521,"CourseChapterTopicPlaylistID":284108,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:01.919","Text":"In the previous videos,"},{"Start":"00:01.919 ","End":"00:05.895","Text":"we\u0027ve been talking about various kinds of perception."},{"Start":"00:05.895 ","End":"00:11.115","Text":"For instance, we talked about touch and we talked about hearing."},{"Start":"00:11.115 ","End":"00:14.505","Text":"Now we\u0027re going to be discussing vision,"},{"Start":"00:14.505 ","End":"00:18.720","Text":"how light is perceived by our ears."},{"Start":"00:18.720 ","End":"00:20.640","Text":"First of all, what is vision?"},{"Start":"00:20.640 ","End":"00:22.890","Text":"Vision is certainly the ability to detect"},{"Start":"00:22.890 ","End":"00:26.490","Text":"light patterns and then interpret them into images."},{"Start":"00:26.490 ","End":"00:28.320","Text":"We\u0027re not the only animals that can do that."},{"Start":"00:28.320 ","End":"00:30.405","Text":"You can see this spider, for instance,"},{"Start":"00:30.405 ","End":"00:33.930","Text":"has these eyes on its head."},{"Start":"00:33.930 ","End":"00:35.775","Text":"It sees, of course,"},{"Start":"00:35.775 ","End":"00:37.815","Text":"it doesn\u0027t see the same way we do."},{"Start":"00:37.815 ","End":"00:42.375","Text":"That\u0027s one of the things that we\u0027ll discuss briefly in this video."},{"Start":"00:42.375 ","End":"00:49.955","Text":"The general mechanism for capturing light is actually the same in all animals."},{"Start":"00:49.955 ","End":"00:52.130","Text":"It\u0027s just what we do with"},{"Start":"00:52.130 ","End":"00:57.380","Text":"that captured light and so that of course suggests an evolutionary origin."},{"Start":"00:57.380 ","End":"01:00.080","Text":"You can see here there are all sorts of eyes in"},{"Start":"01:00.080 ","End":"01:04.220","Text":"this pattern and they look in a certain way,"},{"Start":"01:04.220 ","End":"01:05.840","Text":"the same way, the same."},{"Start":"01:05.840 ","End":"01:08.075","Text":"You can see this and this and so on."},{"Start":"01:08.075 ","End":"01:09.590","Text":"They look, certainly,"},{"Start":"01:09.590 ","End":"01:12.290","Text":"you can tell that they\u0027re all eyes,"},{"Start":"01:12.290 ","End":"01:14.630","Text":"but in other ways, they look quite different."},{"Start":"01:14.630 ","End":"01:17.855","Text":"Here you can see there\u0027s a slit that goes up and down."},{"Start":"01:17.855 ","End":"01:20.390","Text":"In other eyes, like for instance ours you know that there\u0027s"},{"Start":"01:20.390 ","End":"01:24.304","Text":"a pupil which can get smaller and larger,"},{"Start":"01:24.304 ","End":"01:29.900","Text":"but it goes in a spherical way or circular way,"},{"Start":"01:29.900 ","End":"01:31.970","Text":"not as a slit."},{"Start":"01:31.970 ","End":"01:34.490","Text":"The visual systems actually have"},{"Start":"01:34.490 ","End":"01:38.435","Text":"evolved to attend to the most important visual information."},{"Start":"01:38.435 ","End":"01:46.520","Text":"That is, an animal has to deal with what it sees outside and what\u0027s important for it."},{"Start":"01:46.520 ","End":"01:52.025","Text":"There are lots of visual inputs but the eye has adapted for each individual animal"},{"Start":"01:52.025 ","End":"01:58.535","Text":"to be able to interpret what it sees and that\u0027s important for it."},{"Start":"01:58.535 ","End":"02:01.670","Text":"Let\u0027s see. The general mechanism,"},{"Start":"02:01.670 ","End":"02:03.595","Text":"as we said, is the same."},{"Start":"02:03.595 ","End":"02:11.495","Text":"What happens is that there are these countless inputs that go from the eye to the brain."},{"Start":"02:11.495 ","End":"02:13.310","Text":"In fact, in humans,"},{"Start":"02:13.310 ","End":"02:17.330","Text":"about 30 percent of the cerebral cortex of"},{"Start":"02:17.330 ","End":"02:21.860","Text":"the brain back here is dedicated to analyzing and perceiving visual information."},{"Start":"02:21.860 ","End":"02:26.045","Text":"It\u0027s very important for us in other animals,"},{"Start":"02:26.045 ","End":"02:27.960","Text":"it\u0027s a lot less important."},{"Start":"02:27.960 ","End":"02:30.785","Text":"If you remember when we talked about sounds,"},{"Start":"02:30.785 ","End":"02:35.075","Text":"we learned that there were different wavelengths and different amplitudes"},{"Start":"02:35.075 ","End":"02:40.660","Text":"of sounds and that humans could only detect a certain part of that."},{"Start":"02:40.660 ","End":"02:43.955","Text":"Well, a similar thing is true with light."},{"Start":"02:43.955 ","End":"02:49.265","Text":"There are different wavelengths that are measured in nanometers."},{"Start":"02:49.265 ","End":"02:52.069","Text":"Just as those wavelengths were involved,"},{"Start":"02:52.069 ","End":"02:54.425","Text":"were important for the frequency,"},{"Start":"02:54.425 ","End":"02:58.115","Text":"that is the pitch of the sound that we heard in the case of light,"},{"Start":"02:58.115 ","End":"03:03.530","Text":"it has to do with the color that we perceive and that\u0027s the wavelength."},{"Start":"03:03.530 ","End":"03:07.895","Text":"There is a range which goes here from"},{"Start":"03:07.895 ","End":"03:12.140","Text":"roughly 400 to 700 nanometers in"},{"Start":"03:12.140 ","End":"03:15.170","Text":"this particular illustration and"},{"Start":"03:15.170 ","End":"03:18.455","Text":"that demonstrates more or less what the human eye can see."},{"Start":"03:18.455 ","End":"03:22.550","Text":"Humans actually can perceive light that ranges between"},{"Start":"03:22.550 ","End":"03:27.995","Text":"about 380 nanometers and 740 nanometers."},{"Start":"03:27.995 ","End":"03:33.455","Text":"More specific than what this shows but you can see the different colors that are here."},{"Start":"03:33.455 ","End":"03:38.135","Text":"Different animals can see outside of that range."},{"Start":"03:38.135 ","End":"03:40.850","Text":"For instance, in the longer wavelengths,"},{"Start":"03:40.850 ","End":"03:42.770","Text":"we have infrared,"},{"Start":"03:42.770 ","End":"03:47.925","Text":"microwaves, radio waves are all on the same spectrum."},{"Start":"03:47.925 ","End":"03:50.480","Text":"Then in the shorter wavelengths,"},{"Start":"03:50.480 ","End":"03:51.590","Text":"in the shorter frequencies,"},{"Start":"03:51.590 ","End":"03:54.885","Text":"we have ultraviolet x-rays and Gamma rays."},{"Start":"03:54.885 ","End":"03:56.910","Text":"What do the other animals see?"},{"Start":"03:56.910 ","End":"03:58.220","Text":"Well, for instance,"},{"Start":"03:58.220 ","End":"04:02.720","Text":"this is what humans see and we\u0027ll learn later that there are different peaks because"},{"Start":"04:02.720 ","End":"04:07.490","Text":"we\u0027ve got different kinds of pigments that can detect the light."},{"Start":"04:07.490 ","End":"04:09.860","Text":"Well, the bugs, for instance,"},{"Start":"04:09.860 ","End":"04:15.780","Text":"overlap with us in some respects but they can also see shorter wavelengths."},{"Start":"04:15.780 ","End":"04:18.110","Text":"It very much depends on"},{"Start":"04:18.110 ","End":"04:24.105","Text":"the animal exactly what it can see and we\u0027ll come back to that a little bit later."},{"Start":"04:24.105 ","End":"04:33.065","Text":"The colors that we see are the frequencies which reach our eyes,"},{"Start":"04:33.065 ","End":"04:34.890","Text":"the ones that reach our eyes."},{"Start":"04:34.890 ","End":"04:37.580","Text":"If we see something that\u0027s green, for instance,"},{"Start":"04:37.580 ","End":"04:45.440","Text":"then what our eye is going to see is going to see what is not absorbed by the leaf."},{"Start":"04:45.440 ","End":"04:48.650","Text":"It\u0027s what is returned from the leaf."},{"Start":"04:48.650 ","End":"04:51.110","Text":"In this case, we see the green color and if we\u0027re talking"},{"Start":"04:51.110 ","End":"04:53.960","Text":"about a flower we\u0027ll see a red color if it\u0027s a red flower."},{"Start":"04:53.960 ","End":"04:56.000","Text":"As we can see up here,"},{"Start":"04:56.000 ","End":"04:58.280","Text":"that\u0027s what the white light,"},{"Start":"04:58.280 ","End":"05:05.520","Text":"which contains all the different frequencies will reflect and that\u0027s what we\u0027ll see."},{"Start":"05:05.520 ","End":"05:10.340","Text":"The appearance color of an object is the color that is reflected."},{"Start":"05:10.340 ","End":"05:14.295","Text":"Now we see an image,"},{"Start":"05:14.295 ","End":"05:19.760","Text":"you know that there\u0027s a difference between a blurry image and a sharp image."},{"Start":"05:19.760 ","End":"05:21.550","Text":"Well, how does that work?"},{"Start":"05:21.550 ","End":"05:24.950","Text":"If this is our eyeball that we can see here,"},{"Start":"05:24.950 ","End":"05:28.985","Text":"then the light comes in through what\u0027s called the cornea,"},{"Start":"05:28.985 ","End":"05:33.035","Text":"which is a transparent layer that protects the eye on the outside."},{"Start":"05:33.035 ","End":"05:35.405","Text":"Then it goes through a lens,"},{"Start":"05:35.405 ","End":"05:37.970","Text":"very much like you might have in a camera."},{"Start":"05:37.970 ","End":"05:43.855","Text":"Through this lens then you get a focusing of the lights,"},{"Start":"05:43.855 ","End":"05:47.345","Text":"which focuses into a particular spot,"},{"Start":"05:47.345 ","End":"05:51.950","Text":"hopefully on the back of the eye in an area called the retina."},{"Start":"05:51.950 ","End":"05:55.085","Text":"If it focuses in the right place,"},{"Start":"05:55.085 ","End":"05:57.665","Text":"then we\u0027ll get a sharp image."},{"Start":"05:57.665 ","End":"06:00.950","Text":"If not, we\u0027ll get a blurry image and we\u0027ll see that in a minute."},{"Start":"06:00.950 ","End":"06:02.465","Text":"Now, in addition,"},{"Start":"06:02.465 ","End":"06:07.550","Text":"there is an iris that is something which opens and closes."},{"Start":"06:07.550 ","End":"06:12.170","Text":"It\u0027s a circular muscular ring that lies between the lens and the cornea,"},{"Start":"06:12.170 ","End":"06:14.360","Text":"and that regulates the amount of light that comes in."},{"Start":"06:14.360 ","End":"06:19.265","Text":"We don\u0027t want to bleach our retina having too much light that comes through there."},{"Start":"06:19.265 ","End":"06:21.320","Text":"If there\u0027s a very bright day,"},{"Start":"06:21.320 ","End":"06:23.964","Text":"you know that it\u0027s very hard to see until"},{"Start":"06:23.964 ","End":"06:28.060","Text":"our iris closes down and only lets some of the light in."},{"Start":"06:28.060 ","End":"06:31.760","Text":"On the other hand, if we are trying to see at night,"},{"Start":"06:31.760 ","End":"06:37.855","Text":"we want the opposite so then the iris will open wide to let more light in so we can see."},{"Start":"06:37.855 ","End":"06:39.600","Text":"In conditions of high light,"},{"Start":"06:39.600 ","End":"06:44.530","Text":"the iris contracts whereas in low light, it relaxes."},{"Start":"06:45.380 ","End":"06:47.490","Text":"What\u0027s called the pupil,"},{"Start":"06:47.490 ","End":"06:54.070","Text":"the area in which the iris is found will change its size."}],"ID":30027},{"Watched":false,"Name":"Structure of the eye","Duration":"8m 28s","ChapterTopicVideoID":28524,"CourseChapterTopicPlaylistID":284108,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.645","Text":"Let\u0027s continue our discussion of vision."},{"Start":"00:03.645 ","End":"00:05.775","Text":"In the previous video,"},{"Start":"00:05.775 ","End":"00:09.315","Text":"we were talking about the anatomy of the eye,"},{"Start":"00:09.315 ","End":"00:12.675","Text":"and we talked about the iris,"},{"Start":"00:12.675 ","End":"00:16.185","Text":"yes which controls the size of the pupil,"},{"Start":"00:16.185 ","End":"00:19.275","Text":"letting more or less light in."},{"Start":"00:19.275 ","End":"00:24.910","Text":"Now let\u0027s continue talking about the lens itself."},{"Start":"00:24.910 ","End":"00:28.490","Text":"The lens itself, which is"},{"Start":"00:28.490 ","End":"00:33.005","Text":"a transparent disc of protein and its function like other lenses,"},{"Start":"00:33.005 ","End":"00:38.885","Text":"is to focus the light which comes in such that it focuses"},{"Start":"00:38.885 ","End":"00:46.070","Text":"precisely at the fovea centralis at the back of the eye."},{"Start":"00:46.070 ","End":"00:52.025","Text":"What happens here is that there is dynamic focusing. What does that mean?"},{"Start":"00:52.025 ","End":"00:54.920","Text":"That means that the focus point can"},{"Start":"00:54.920 ","End":"00:59.675","Text":"change to go either behind the eye or in front of the eye,"},{"Start":"00:59.675 ","End":"01:04.410","Text":"depending on the shape of the lens."},{"Start":"01:04.490 ","End":"01:12.860","Text":"That\u0027s going to control whether we can see things which are near or far in focus."},{"Start":"01:12.860 ","End":"01:21.725","Text":"You all know that you can see things very clearly close to you if you can focus on them."},{"Start":"01:21.725 ","End":"01:24.770","Text":"If you can\u0027t focus on them, they\u0027ll look blurry."},{"Start":"01:24.770 ","End":"01:28.490","Text":"There\u0027s this issue of nearsightedness and farsightedness."},{"Start":"01:28.490 ","End":"01:31.520","Text":"There were all familiar with and we\u0027ll look at that in a minute."},{"Start":"01:31.520 ","End":"01:34.510","Text":"Now in front of the lens,"},{"Start":"01:34.700 ","End":"01:41.210","Text":"there is a clear and watery substance called aqueous humor and behind it,"},{"Start":"01:41.210 ","End":"01:43.385","Text":"something which is more jelly-like,"},{"Start":"01:43.385 ","End":"01:49.125","Text":"that\u0027s behind the lens over here and that\u0027s called vitreous humor."},{"Start":"01:49.125 ","End":"01:56.540","Text":"There is something which is in front and behind the lens, a bigger partner."},{"Start":"01:56.540 ","End":"01:59.195","Text":"The vitreous humor, as you can see is here."},{"Start":"01:59.195 ","End":"02:01.040","Text":"This is the lens."},{"Start":"02:01.040 ","End":"02:06.430","Text":"What I was pointing to before is just the pupil."},{"Start":"02:06.430 ","End":"02:08.315","Text":"As I mentioned earlier,"},{"Start":"02:08.315 ","End":"02:14.540","Text":"there are muscles which change the shape of the lens and how and where are they?"},{"Start":"02:14.540 ","End":"02:17.840","Text":"As you can see, they\u0027re attached to the lens on"},{"Start":"02:17.840 ","End":"02:21.845","Text":"the side and they allow it to be either flatter"},{"Start":"02:21.845 ","End":"02:29.525","Text":"or more broad such that the light then is focused at the back of the eye as we mentioned."},{"Start":"02:29.525 ","End":"02:33.275","Text":"This changes what\u0027s called the focal length"},{"Start":"02:33.275 ","End":"02:39.170","Text":"of the light that\u0027s coming in to focus on the retina."},{"Start":"02:39.170 ","End":"02:40.640","Text":"Now, as we mentioned before,"},{"Start":"02:40.640 ","End":"02:44.480","Text":"there is nearsightedness and farsightedness."},{"Start":"02:44.480 ","End":"02:50.495","Text":"In a technical term called presbyopia,"},{"Start":"02:50.495 ","End":"02:56.690","Text":"you see that the focus is behind the lens and this"},{"Start":"02:56.690 ","End":"03:03.215","Text":"occurs with age when the lens is no longer so well-focused and in that case,"},{"Start":"03:03.215 ","End":"03:07.490","Text":"what happens is that the images in the distance are clear."},{"Start":"03:07.490 ","End":"03:11.450","Text":"You can see things well in the distance that\u0027s farsightedness,"},{"Start":"03:11.450 ","End":"03:14.235","Text":"but the images nearby are blurry."},{"Start":"03:14.235 ","End":"03:16.890","Text":"That\u0027s why older people often wear"},{"Start":"03:16.890 ","End":"03:21.890","Text":"corrective reading glasses so that they can bring this focus"},{"Start":"03:21.890 ","End":"03:29.985","Text":"from behind the eye to the back of the eye on the retina."},{"Start":"03:29.985 ","End":"03:33.000","Text":"How is this light sensed?"},{"Start":"03:33.000 ","End":"03:41.104","Text":"There are cells that are called photoreceptors and there are actually 2 different kinds."},{"Start":"03:41.104 ","End":"03:47.210","Text":"There are what are called rods and cones because of their general appearance."},{"Start":"03:47.210 ","End":"03:49.985","Text":"Let\u0027s first look at rods."},{"Start":"03:49.985 ","End":"03:55.630","Text":"Rods are very, very sensitive to the lights,"},{"Start":"03:55.630 ","End":"04:00.530","Text":"and they are located actually on the outer edges of"},{"Start":"04:00.530 ","End":"04:07.160","Text":"the retina not in the center necessarily where things are being focused."},{"Start":"04:07.160 ","End":"04:09.905","Text":"They\u0027re very sensitive to light, as we said."},{"Start":"04:09.905 ","End":"04:14.480","Text":"Therefore, they can detect very dim lights and they are"},{"Start":"04:14.480 ","End":"04:18.950","Text":"responsible for peripheral vision and for nighttime vision."},{"Start":"04:18.950 ","End":"04:24.970","Text":"You want to be able to see something at least at night when there is very little light."},{"Start":"04:24.970 ","End":"04:27.380","Text":"You\u0027ll notice, I think,"},{"Start":"04:27.380 ","End":"04:31.500","Text":"that when you see something at night,"},{"Start":"04:31.500 ","End":"04:34.100","Text":"things tend to look black and white."},{"Start":"04:34.100 ","End":"04:36.770","Text":"You don\u0027t see very much color and it in fact,"},{"Start":"04:36.770 ","End":"04:40.805","Text":"these rods really don\u0027t see color."},{"Start":"04:40.805 ","End":"04:42.260","Text":"There are many of them."},{"Start":"04:42.260 ","End":"04:45.230","Text":"There are about a 100 million in the human eye."},{"Start":"04:45.230 ","End":"04:48.110","Text":"Now let\u0027s look at cones."},{"Start":"04:48.110 ","End":"04:51.230","Text":"Cones, rather than being very sensitive,"},{"Start":"04:51.230 ","End":"04:54.725","Text":"are not very sensitive."},{"Start":"04:54.725 ","End":"04:56.975","Text":"They\u0027re weakly photosensitive,"},{"Start":"04:56.975 ","End":"05:00.815","Text":"and they\u0027re located not at the periphery of the eye,"},{"Start":"05:00.815 ","End":"05:06.125","Text":"but rather closer to the center of the retina that we call the fovea."},{"Start":"05:06.125 ","End":"05:09.860","Text":"They respond primarily to very bright rights."},{"Start":"05:09.860 ","End":"05:15.860","Text":"They respond primarily to bright lights and their primary role is in the daytime,"},{"Start":"05:15.860 ","End":"05:19.805","Text":"and of course they do enable color vision."},{"Start":"05:19.805 ","End":"05:21.740","Text":"So here\u0027s the cone,"},{"Start":"05:21.740 ","End":"05:25.075","Text":"as opposed to the rod that we saw earlier,"},{"Start":"05:25.075 ","End":"05:30.600","Text":"and there are about 6-7 million of these in the eye."},{"Start":"05:31.480 ","End":"05:34.130","Text":"At the back of the eye,"},{"Start":"05:34.130 ","End":"05:37.369","Text":"there is the fovea centralis,"},{"Start":"05:37.369 ","End":"05:41.405","Text":"which actually is sometimes called the macula."},{"Start":"05:41.405 ","End":"05:45.255","Text":"You may know older people that have macular degeneration."},{"Start":"05:45.255 ","End":"05:50.000","Text":"That\u0027s when this back of the eye becomes degenerated and they can\u0027t"},{"Start":"05:50.000 ","End":"05:56.180","Text":"see very clearly when they\u0027re trying to look at very specific things."},{"Start":"05:56.180 ","End":"05:58.550","Text":"That of course, is located at the back of"},{"Start":"05:58.550 ","End":"06:00.800","Text":"the eye and is responsible for the acute vision,"},{"Start":"06:00.800 ","End":"06:02.420","Text":"as we said before,"},{"Start":"06:02.420 ","End":"06:07.865","Text":"and has a particularly high density of cones."},{"Start":"06:07.865 ","End":"06:10.730","Text":"Now, let\u0027s look at these cones."},{"Start":"06:10.730 ","End":"06:15.290","Text":"These cones are connected to"},{"Start":"06:15.290 ","End":"06:20.240","Text":"other cells that are called bipolar cells and we\u0027ll come back to them later."},{"Start":"06:20.240 ","End":"06:23.840","Text":"They\u0027re called bipolar because they interact both with"},{"Start":"06:23.840 ","End":"06:27.590","Text":"these cone cells are actually with rods as well in other places,"},{"Start":"06:27.590 ","End":"06:30.775","Text":"and also with ganglia,"},{"Start":"06:30.775 ","End":"06:33.870","Text":"that is nerve cells the other and they\u0027re going to transmit"},{"Start":"06:33.870 ","End":"06:38.520","Text":"a signal and we\u0027ll discuss that a bit more later."},{"Start":"06:38.520 ","End":"06:45.950","Text":"The eyes can orient an object so that it\u0027s image falls on the fovea by focusing,"},{"Start":"06:45.950 ","End":"06:47.705","Text":"as we\u0027ve mentioned before."},{"Start":"06:47.705 ","End":"06:51.190","Text":"Interestingly in humans,"},{"Start":"06:51.190 ","End":"06:58.750","Text":"the rods are found only in the more peripheral parts of the retina,"},{"Start":"06:58.750 ","End":"07:00.615","Text":"not in the fovea."},{"Start":"07:00.615 ","End":"07:05.990","Text":"That allows us to see very clearly and in very high resolution things"},{"Start":"07:05.990 ","End":"07:11.405","Text":"that were specifically looking at and also to see them in full color."},{"Start":"07:11.405 ","End":"07:15.690","Text":"On the other hands in nocturnal animals,"},{"Start":"07:15.690 ","End":"07:20.959","Text":"the fovea is almost entirely composed of the rods and they therefore,"},{"Start":"07:20.959 ","End":"07:27.745","Text":"these nocturnal animals have very poor color vision, virtually none."},{"Start":"07:27.745 ","End":"07:30.590","Text":"Let\u0027s think about peripheral vision a minute."},{"Start":"07:30.590 ","End":"07:33.755","Text":"If you\u0027re looking at something very specific, you know,"},{"Start":"07:33.755 ","End":"07:38.030","Text":"that things that are occurring on the side, on top,"},{"Start":"07:38.030 ","End":"07:40.145","Text":"bottom, or on the sides,"},{"Start":"07:40.145 ","End":"07:45.980","Text":"you can detect somebody flies into your vision on the side, you can see it."},{"Start":"07:45.980 ","End":"07:48.950","Text":"You don\u0027t necessarily know precisely what happened,"},{"Start":"07:48.950 ","End":"07:56.640","Text":"but something happened there and that is seen by the rod cells that are there."},{"Start":"07:56.640 ","End":"08:00.920","Text":"That\u0027s produced by the rods which are located on the edges of the retina."},{"Start":"08:00.920 ","End":"08:02.360","Text":"It\u0027s not as sharp."},{"Start":"08:02.360 ","End":"08:05.060","Text":"You can\u0027t tell precisely what\u0027s going on there,"},{"Start":"08:05.060 ","End":"08:07.670","Text":"but you know that something\u0027s happening there and"},{"Start":"08:07.670 ","End":"08:10.230","Text":"they\u0027re particularly sensitive to light."},{"Start":"08:10.230 ","End":"08:15.355","Text":"Remember, we said that they function in low light and to motion."},{"Start":"08:15.355 ","End":"08:19.760","Text":"This is very important for us because let\u0027s say we\u0027re driving"},{"Start":"08:19.760 ","End":"08:23.610","Text":"down the road and some car comes into our peripheral vision,"},{"Start":"08:23.610 ","End":"08:28.230","Text":"we want to be able to react and see it."}],"ID":30028},{"Watched":false,"Name":"Rhodopsin and Signal Transduction","Duration":"7m 18s","ChapterTopicVideoID":28523,"CourseChapterTopicPlaylistID":284108,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.320","Text":"Glad that you\u0027re back to continue our discussion about vision."},{"Start":"00:04.320 ","End":"00:07.110","Text":"So far we know that the light hits"},{"Start":"00:07.110 ","End":"00:11.880","Text":"the retina and we know that there are some cells there that can detect the lights,"},{"Start":"00:11.880 ","End":"00:15.240","Text":"but we haven\u0027t yet discussed how the light is"},{"Start":"00:15.240 ","End":"00:19.365","Text":"turned into a signal that is picked up by nerves,"},{"Start":"00:19.365 ","End":"00:21.405","Text":"and that\u0027s what we\u0027re going do here."},{"Start":"00:21.405 ","End":"00:29.070","Text":"We\u0027ll see that the transduction of the light signal into a nervous signal is"},{"Start":"00:29.070 ","End":"00:37.530","Text":"done via a molecule of photopigment that\u0027s called rhodopsin."},{"Start":"00:38.390 ","End":"00:44.555","Text":"Both of them, both rods and cones contain these photopigments,"},{"Start":"00:44.555 ","End":"00:48.695","Text":"and it turns out these pigments are unstable. What does that mean?"},{"Start":"00:48.695 ","End":"00:53.310","Text":"That means that they can change or something in them can change,"},{"Start":"00:53.310 ","End":"00:56.725","Text":"actually, it\u0027s a molecule called retinal,"},{"Start":"00:56.725 ","End":"01:06.510","Text":"which changes its structure depending on whether it\u0027s hits by light or it\u0027s not."},{"Start":"01:06.510 ","End":"01:08.879","Text":"There are 2 isomers,"},{"Start":"01:08.879 ","End":"01:11.210","Text":"that is, 2 different structures."},{"Start":"01:11.210 ","End":"01:17.810","Text":"There\u0027s a cis and a trans isomer of retinal,"},{"Start":"01:17.810 ","End":"01:24.590","Text":"and you can see that in the cis conformation you have a bend in the molecule,"},{"Start":"01:24.590 ","End":"01:28.234","Text":"whereas the trans isomer,"},{"Start":"01:28.234 ","End":"01:30.260","Text":"which goes back and forth and back and forth,"},{"Start":"01:30.260 ","End":"01:32.135","Text":"and that\u0027s why it\u0027s called trans,"},{"Start":"01:32.135 ","End":"01:34.700","Text":"is a straight molecule,"},{"Start":"01:34.700 ","End":"01:40.625","Text":"and it\u0027s that change which is caused by light which is going to be detected."},{"Start":"01:40.625 ","End":"01:44.195","Text":"There\u0027s going to be a signal transduction pathway."},{"Start":"01:44.195 ","End":"01:46.385","Text":"So in vertebrates,"},{"Start":"01:46.385 ","End":"01:48.080","Text":"the main photopigment,"},{"Start":"01:48.080 ","End":"01:51.770","Text":"as I mentioned, is called rhodopsin and it has 2 parts."},{"Start":"01:51.770 ","End":"01:55.300","Text":"It has this retinal that we just discussed."},{"Start":"01:55.300 ","End":"01:58.320","Text":"That\u0027s the second thing that\u0027s discussed here."},{"Start":"01:58.320 ","End":"02:04.275","Text":"The retinal is embedded in a transmembrane protein."},{"Start":"02:04.275 ","End":"02:10.235","Text":"Here you can see the membrane and this opsin, this membrane protein,"},{"Start":"02:10.235 ","End":"02:16.385","Text":"has a number of Alpha-helices in it which go across the span of the membrane,"},{"Start":"02:16.385 ","End":"02:21.305","Text":"and in the middle of it is the retinal,"},{"Start":"02:21.305 ","End":"02:27.245","Text":"which can change shape as a function of light."},{"Start":"02:27.245 ","End":"02:32.285","Text":"The isomerization of retinal activates this whole rhodopsin,"},{"Start":"02:32.285 ","End":"02:33.830","Text":"and at the end of the day,"},{"Start":"02:33.830 ","End":"02:36.260","Text":"what\u0027s going to happen is that there\u0027s going to be"},{"Start":"02:36.260 ","End":"02:40.625","Text":"a closing of sodium channels in the photoreceptor membrane."},{"Start":"02:40.625 ","End":"02:42.805","Text":"We\u0027ll see in a minute how that happens."},{"Start":"02:42.805 ","End":"02:47.360","Text":"Now you know that in most cases when there\u0027s a stimulus,"},{"Start":"02:47.360 ","End":"02:51.620","Text":"you get depolarization of sensory neurons."},{"Start":"02:51.620 ","End":"02:54.110","Text":"That\u0027s what we\u0027ve seen before in smell,"},{"Start":"02:54.110 ","End":"02:55.580","Text":"and hearing, and so on."},{"Start":"02:55.580 ","End":"02:57.235","Text":"Here it\u0027s different."},{"Start":"02:57.235 ","End":"03:01.085","Text":"Here there is hyperpolarization."},{"Start":"03:01.085 ","End":"03:04.460","Text":"What does that mean? That means that we had"},{"Start":"03:04.460 ","End":"03:11.000","Text":"a depolarized situation and it gets more depolarized,"},{"Start":"03:11.000 ","End":"03:20.945","Text":"it gets hyperpolarized as results of light striking as a result of the retinal,"},{"Start":"03:20.945 ","End":"03:22.865","Text":"as we see here."},{"Start":"03:22.865 ","End":"03:27.875","Text":"What happens? When light strikes the rhodopsin,"},{"Start":"03:27.875 ","End":"03:37.010","Text":"there is a signal transduction pathway that occurs via a molecule called transducin,"},{"Start":"03:37.010 ","End":"03:39.185","Text":"which is activated,"},{"Start":"03:39.185 ","End":"03:45.185","Text":"and that activates a enzyme called phosphodiesterase."},{"Start":"03:45.185 ","End":"03:48.650","Text":"Phosphodiesterase is an esterase, in other words,"},{"Start":"03:48.650 ","End":"03:55.825","Text":"it changes the esterification of a molecule called cyclic GMP."},{"Start":"03:55.825 ","End":"03:59.045","Text":"It basically opens up this cyclic GMP,"},{"Start":"03:59.045 ","End":"04:00.875","Text":"makes regular GMP out of it."},{"Start":"04:00.875 ","End":"04:04.295","Text":"Now why is that important for our discussion?"},{"Start":"04:04.295 ","End":"04:11.760","Text":"Because it turns out that cyclic GMP"},{"Start":"04:11.760 ","End":"04:21.870","Text":"is important in the structure of the sodium channel of these cells."},{"Start":"04:21.870 ","End":"04:26.000","Text":"When there\u0027s a lot of cyclic GMP around,"},{"Start":"04:26.000 ","End":"04:32.770","Text":"what happens is that sodium cannot enter the cell,"},{"Start":"04:33.680 ","End":"04:40.620","Text":"and therefore we get a certain membrane potential as a result."},{"Start":"04:40.620 ","End":"04:46.590","Text":"What happens when light"},{"Start":"04:46.590 ","End":"04:52.877","Text":"hits the rod or the cone,"},{"Start":"04:52.877 ","End":"04:57.770","Text":"then there\u0027s the isomerization of the retinal,"},{"Start":"04:57.770 ","End":"04:59.690","Text":"as we saw here,"},{"Start":"04:59.690 ","End":"05:07.070","Text":"and then the phosphodiesterase converts cyclic GMP to GMP,"},{"Start":"05:07.070 ","End":"05:11.285","Text":"closing the sodium channels before they were opened,"},{"Start":"05:11.285 ","End":"05:13.895","Text":"and we\u0027ll see that in the next slide."},{"Start":"05:13.895 ","End":"05:19.750","Text":"Once the cyclic GMP turns into GMP,"},{"Start":"05:19.750 ","End":"05:24.770","Text":"then the channel now is closed and the"},{"Start":"05:24.770 ","End":"05:30.365","Text":"polarization that we had before becomes even greater into hyperpolarization."},{"Start":"05:30.365 ","End":"05:33.470","Text":"The hyperpolarized membrane then causes"},{"Start":"05:33.470 ","End":"05:38.735","Text":"these cells to stop releasing glutamate at their end."},{"Start":"05:38.735 ","End":"05:44.210","Text":"They had been releasing a molecule called glutamate that was picked up by the polar cell."},{"Start":"05:44.210 ","End":"05:46.247","Text":"Remember we mentioned the polar cell behind it."},{"Start":"05:46.247 ","End":"05:49.620","Text":"They stop releasing the glutamate,"},{"Start":"05:49.620 ","End":"05:55.895","Text":"and the bipolar cells then send a signal to the optic nerve,"},{"Start":"05:55.895 ","End":"05:59.960","Text":"saying that they have received some light."},{"Start":"05:59.960 ","End":"06:02.565","Text":"In this slide now,"},{"Start":"06:02.565 ","End":"06:09.365","Text":"we can see what the situation was before there was light in dark."},{"Start":"06:09.365 ","End":"06:13.250","Text":"In the dark, the sodium ions were able to"},{"Start":"06:13.250 ","End":"06:17.375","Text":"get into the cell because cyclic GMP was bound to them,"},{"Start":"06:17.375 ","End":"06:22.475","Text":"and that maintain a particular depolarized state."},{"Start":"06:22.475 ","End":"06:27.840","Text":"However, once light hits the retinal,"},{"Start":"06:27.840 ","End":"06:30.905","Text":"it then changes its conformation."},{"Start":"06:30.905 ","End":"06:36.245","Text":"There\u0027s a signal transduction pathway causing an activated the phosphodiesterase,"},{"Start":"06:36.245 ","End":"06:42.860","Text":"which breaks the cyclic AMP into just GMP."},{"Start":"06:42.860 ","End":"06:48.860","Text":"The GMP then is no longer able to bind the sodium channel."},{"Start":"06:48.860 ","End":"06:56.905","Text":"The sodium channel closes and the membrane becomes polarized even further."},{"Start":"06:56.905 ","End":"07:03.034","Text":"That causes the glutamate now to no longer be produced,"},{"Start":"07:03.034 ","End":"07:05.630","Text":"and that signal is picked up by polar cell,"},{"Start":"07:05.630 ","End":"07:09.635","Text":"which is connected to the synaptic terminals,"},{"Start":"07:09.635 ","End":"07:17.820","Text":"and then signals the ganglia that are beyond them that light has been seen."}],"ID":30029},{"Watched":false,"Name":"Color Perception","Duration":"7m 21s","ChapterTopicVideoID":28525,"CourseChapterTopicPlaylistID":284108,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.080","Text":"Welcome back to our discussion of vision."},{"Start":"00:04.080 ","End":"00:07.905","Text":"Until now we\u0027ve been discussing the structure of the eye,"},{"Start":"00:07.905 ","End":"00:13.140","Text":"but we haven\u0027t really mentioned how the light is detected."},{"Start":"00:13.140 ","End":"00:15.405","Text":"How is the light really detected?"},{"Start":"00:15.405 ","End":"00:21.000","Text":"Well, we did say that there is this pigment called"},{"Start":"00:21.000 ","End":"00:27.150","Text":"rhodopsin and that it has the retinol in it which changes its conformation."},{"Start":"00:27.150 ","End":"00:30.660","Text":"But it turns out actually that in the cones,"},{"Start":"00:30.660 ","End":"00:34.380","Text":"remember the cells that are responsible for our color vision,"},{"Start":"00:34.380 ","End":"00:38.030","Text":"there are 3 different pigments,"},{"Start":"00:38.030 ","End":"00:43.819","Text":"each of which has an optimal wavelength at which it absorbs."},{"Start":"00:43.819 ","End":"00:46.549","Text":"There are the short cones,"},{"Start":"00:46.549 ","End":"00:49.084","Text":"there are the medium cones,"},{"Start":"00:49.084 ","End":"00:51.530","Text":"and there are the long cones."},{"Start":"00:51.530 ","End":"00:56.600","Text":"Each of them responds to different wavelengths."},{"Start":"00:56.600 ","End":"01:02.780","Text":"That is the optimal wavelength of the short is at 420 nanometers,"},{"Start":"01:02.780 ","End":"01:07.430","Text":"the medium at 534 roughly,"},{"Start":"01:07.430 ","End":"01:12.860","Text":"and the large, the long at 560 roughly."},{"Start":"01:12.860 ","End":"01:17.555","Text":"What does that mean? That means that if light of,"},{"Start":"01:17.555 ","End":"01:21.814","Text":"let\u0027s say 420 nanometers strikes these cells,"},{"Start":"01:21.814 ","End":"01:27.680","Text":"the short cones, then the pigment will optimally pick up the signal."},{"Start":"01:27.680 ","End":"01:29.390","Text":"If the wavelength is,"},{"Start":"01:29.390 ","End":"01:35.750","Text":"let\u0027s say at about 580 then it\u0027ll pick up only about 50 percent of that."},{"Start":"01:35.750 ","End":"01:37.595","Text":"Now, since we have"},{"Start":"01:37.595 ","End":"01:43.415","Text":"all 3 different kinds of cones in our eyes with the 3 different pigments,"},{"Start":"01:43.415 ","End":"01:48.150","Text":"an intermediate wavelength will be picked up to some degree by all of them,"},{"Start":"01:48.150 ","End":"01:51.830","Text":"and then our brain will interpolate that and"},{"Start":"01:51.830 ","End":"01:56.255","Text":"will cause us to understand that there is a particular color."},{"Start":"01:56.255 ","End":"02:03.095","Text":"Now humans have a very broad range of different colors that we can see."},{"Start":"02:03.095 ","End":"02:04.520","Text":"In the picture on the right,"},{"Start":"02:04.520 ","End":"02:08.704","Text":"you can see a particular color of these different flowers."},{"Start":"02:08.704 ","End":"02:11.990","Text":"We have this trichromatic system,"},{"Start":"02:11.990 ","End":"02:14.690","Text":"as we mentioned in the previous slide."},{"Start":"02:14.690 ","End":"02:19.115","Text":"However, dogs only have a dichromatic system."},{"Start":"02:19.115 ","End":"02:23.734","Text":"The dogs have only 2 of these pigments, and therefore,"},{"Start":"02:23.734 ","End":"02:28.950","Text":"their color vision is not as complete as ours is."},{"Start":"02:28.950 ","End":"02:33.635","Text":"The same picture above would look something like this to them,"},{"Start":"02:33.635 ","End":"02:36.740","Text":"where this reddish color would not really be seen,"},{"Start":"02:36.740 ","End":"02:42.425","Text":"it would be seen more as a black and white or a gray color."},{"Start":"02:42.425 ","End":"02:45.740","Text":"The color that we perceive is the result of"},{"Start":"02:45.740 ","End":"02:50.060","Text":"the various ratios of the different colors If we use, for instance,"},{"Start":"02:50.060 ","End":"02:53.540","Text":"let\u0027s say 498 nanometers would be,"},{"Start":"02:53.540 ","End":"02:55.310","Text":"let\u0027s say, a color that we perceive,"},{"Start":"02:55.310 ","End":"03:02.765","Text":"and it would then be picked up by all the 3 different pigments,"},{"Start":"03:02.765 ","End":"03:06.205","Text":"and we would get a particular signal."},{"Start":"03:06.205 ","End":"03:09.755","Text":"We would know then that what we\u0027re seeing is 498."},{"Start":"03:09.755 ","End":"03:14.180","Text":"We have this very sensitive perception of color and we can distinguish"},{"Start":"03:14.180 ","End":"03:20.705","Text":"about 2 million distinct colors if we discussed different levels of brightness of hues,"},{"Start":"03:20.705 ","End":"03:26.495","Text":"that is exactly what the color is that\u0027s moving the frequency back and forth,"},{"Start":"03:26.495 ","End":"03:29.300","Text":"and of course, how saturated it is."},{"Start":"03:29.300 ","End":"03:34.205","Text":"That\u0027s how deep, how much of a particular color there is."},{"Start":"03:34.205 ","End":"03:40.355","Text":"We have very good color vision compared with other animals."},{"Start":"03:40.355 ","End":"03:45.635","Text":"The different types of cone cells that we have are those"},{"Start":"03:45.635 ","End":"03:52.225","Text":"that are responsible for us seeing these different colors."},{"Start":"03:52.225 ","End":"03:55.220","Text":"There is this overlap between"},{"Start":"03:55.220 ","End":"04:01.080","Text":"the different cones and also with the rods as we mentioned earlier."},{"Start":"04:01.460 ","End":"04:05.630","Text":"Now let\u0027s see how the signal that we"},{"Start":"04:05.630 ","End":"04:10.915","Text":"see is processed further and eventually gets to the optic nerve."},{"Start":"04:10.915 ","End":"04:14.510","Text":"The light rays are captured by the rods and cones."},{"Start":"04:14.510 ","End":"04:17.165","Text":"As we mentioned, there are these bipolar cells."},{"Start":"04:17.165 ","End":"04:22.759","Text":"Remember the glutamate, which is going to be released and is going to be sensed."},{"Start":"04:22.759 ","End":"04:26.540","Text":"The degree of the glutamate is going to be a sensed by the bipolar cells,"},{"Start":"04:26.540 ","End":"04:29.390","Text":"and that\u0027s going to change how much"},{"Start":"04:29.390 ","End":"04:32.900","Text":"of the light impulse gets through to the nerve endings."},{"Start":"04:32.900 ","End":"04:35.900","Text":"There are additional cells called horizontal cells"},{"Start":"04:35.900 ","End":"04:39.050","Text":"that we will see would make some connection"},{"Start":"04:39.050 ","End":"04:45.890","Text":"between the different rods and cones and will sharpen the image that we see."},{"Start":"04:45.890 ","End":"04:52.640","Text":"These impulses then are sent through many nerve fibers,"},{"Start":"04:52.640 ","End":"04:55.504","Text":"about a million different nerve fibers,"},{"Start":"04:55.504 ","End":"04:57.110","Text":"each of these ganglion cells,"},{"Start":"04:57.110 ","End":"04:59.335","Text":"eventually to the optic nerve."},{"Start":"04:59.335 ","End":"05:05.270","Text":"The visual signals then leave the cones and rods and they travel to the bipolar cells,"},{"Start":"05:05.270 ","End":"05:10.970","Text":"as we said, and then to the ganglion cells where there is some processing going on."},{"Start":"05:10.970 ","End":"05:18.335","Text":"Then the information is finally transmitted to the brain through the optic nerve."},{"Start":"05:18.335 ","End":"05:23.195","Text":"Now let\u0027s look again at the graphs that we saw"},{"Start":"05:23.195 ","End":"05:27.710","Text":"earlier in which we had a depolarized state,"},{"Start":"05:27.710 ","End":"05:31.175","Text":"at minus 40 millivolts,"},{"Start":"05:31.175 ","End":"05:38.610","Text":"which then becomes hyperpolarized when the light strikes the retina."},{"Start":"05:38.610 ","End":"05:45.275","Text":"We already had a particular depolarized situation and that was a tonic activity."},{"Start":"05:45.275 ","End":"05:53.285","Text":"The absence of the stimuli maintains some firing at a particular baseline."},{"Start":"05:53.285 ","End":"05:58.280","Text":"The photoreceptors, actually, what they do is they"},{"Start":"05:58.280 ","End":"06:04.820","Text":"change the degree of the firing in response to the light."},{"Start":"06:04.820 ","End":"06:11.705","Text":"The firing rate can change depending on whether there is light and dark."},{"Start":"06:11.705 ","End":"06:13.790","Text":"In the dark, the depolarized cell"},{"Start":"06:13.790 ","End":"06:17.390","Text":"releases the neurotransmitter glutamate, as we mentioned;"},{"Start":"06:17.390 ","End":"06:18.605","Text":"but in the light,"},{"Start":"06:18.605 ","End":"06:24.695","Text":"the cell becomes hyperpolarized and the glutamate is no longer released."},{"Start":"06:24.695 ","End":"06:27.410","Text":"That glutamate then,"},{"Start":"06:27.410 ","End":"06:28.805","Text":"as you can see here,"},{"Start":"06:28.805 ","End":"06:35.585","Text":"is picked up or not picked up if there isn\u0027t any in the light by this bipolar cell,"},{"Start":"06:35.585 ","End":"06:37.985","Text":"as we had mentioned earlier."},{"Start":"06:37.985 ","End":"06:39.725","Text":"In the absence of light,"},{"Start":"06:39.725 ","End":"06:44.930","Text":"the bipolar neurons are continuously and actively"},{"Start":"06:44.930 ","End":"06:51.311","Text":"inhibited in the absence of light by the glutamate."},{"Start":"06:51.311 ","End":"06:55.145","Text":"The exposure to light hyperpolarizes"},{"Start":"06:55.145 ","End":"07:01.655","Text":"the membranes and therefore the inhibition is removed."},{"Start":"07:01.655 ","End":"07:08.605","Text":"There\u0027s no glutamate and then there is no inhibition and we do get a signal."},{"Start":"07:08.605 ","End":"07:13.490","Text":"The visual system relies on a change in"},{"Start":"07:13.490 ","End":"07:20.100","Text":"the retinal activity to encode the visual signals to the brain."}],"ID":30030},{"Watched":false,"Name":"Processing of the Images in the Brain","Duration":"6m 45s","ChapterTopicVideoID":28522,"CourseChapterTopicPlaylistID":284108,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.680","Text":"In this final video on the subject of vision,"},{"Start":"00:04.680 ","End":"00:09.165","Text":"we\u0027re going to delve into some details that help us"},{"Start":"00:09.165 ","End":"00:14.655","Text":"see better and that sharpen our vision in a certain way."},{"Start":"00:14.655 ","End":"00:18.000","Text":"Let\u0027s start discussing lateral inhibition."},{"Start":"00:18.000 ","End":"00:19.180","Text":"What\u0027s lateral inhibition?"},{"Start":"00:19.180 ","End":"00:24.345","Text":"When a photoreceptor stimulates 1 of the horizontal cells,"},{"Start":"00:24.345 ","End":"00:27.975","Text":"remember those cells where it went right and left?"},{"Start":"00:27.975 ","End":"00:33.570","Text":"The horizontal cell can inhibit actually neighboring photoreceptors."},{"Start":"00:33.570 ","End":"00:36.010","Text":"Let\u0027s see what that\u0027s all about."},{"Start":"00:36.010 ","End":"00:39.500","Text":"The result of this actually is going to be the sharpening"},{"Start":"00:39.500 ","End":"00:44.225","Text":"of edges and is going to enhance contrast."},{"Start":"00:44.225 ","End":"00:47.510","Text":"Therefore, this phenomenon of"},{"Start":"00:47.510 ","End":"00:52.700","Text":"the lateral inhibition makes regions receiving light appear either lighter or darker,"},{"Start":"00:52.700 ","End":"00:56.230","Text":"depending exactly where they are in the image."},{"Start":"00:56.230 ","End":"01:00.890","Text":"There are special cells called amacrine cells that distribute"},{"Start":"01:00.890 ","End":"01:06.710","Text":"information from 1 bipolar cell to many ganglion cells,"},{"Start":"01:06.710 ","End":"01:11.540","Text":"and that can amplify the signal which was"},{"Start":"01:11.540 ","End":"01:17.455","Text":"detected by fewer of the rod or cone cells."},{"Start":"01:17.455 ","End":"01:22.220","Text":"Now, we\u0027re going to look at a very interesting phenomenon and I\u0027m going to ask"},{"Start":"01:22.220 ","End":"01:27.545","Text":"you to pause the video according to the following instructions."},{"Start":"01:27.545 ","End":"01:33.665","Text":"First, look at this flag for about 45 seconds,"},{"Start":"01:33.665 ","End":"01:39.860","Text":"where you look as carefully as you can at this center of it,"},{"Start":"01:39.860 ","End":"01:44.645","Text":"where this white dot is for about 45 seconds."},{"Start":"01:44.645 ","End":"01:49.985","Text":"Then very quickly shift your gaze to a blank sheet of white paper,"},{"Start":"01:49.985 ","End":"01:52.770","Text":"or something that\u0027s very white."},{"Start":"01:52.770 ","End":"01:55.985","Text":"What you should see is something called an afterimage."},{"Start":"01:55.985 ","End":"01:59.240","Text":"You should see this Norwegian flag in it\u0027s correct colors"},{"Start":"01:59.240 ","End":"02:05.080","Text":"in different colors. You\u0027ll see."},{"Start":"02:05.080 ","End":"02:07.715","Text":"Then at this point, close your eyes for a moment,"},{"Start":"02:07.715 ","End":"02:12.680","Text":"reopen them and then look at a white paper or wall."},{"Start":"02:12.680 ","End":"02:16.270","Text":"What you\u0027ll see is the colors will change."},{"Start":"02:16.270 ","End":"02:18.620","Text":"There will be a red, white,"},{"Start":"02:18.620 ","End":"02:22.460","Text":"and blue change in colors."},{"Start":"02:22.460 ","End":"02:28.040","Text":"The afterimage of the flag will appear in these red, white, and blue colors."},{"Start":"02:28.040 ","End":"02:29.690","Text":"What\u0027s going on here?"},{"Start":"02:29.690 ","End":"02:37.840","Text":"Well, it turns out that there is this theory called opponent process theory."},{"Start":"02:37.840 ","End":"02:40.265","Text":"Different cones that detect"},{"Start":"02:40.265 ","End":"02:43.985","Text":"the different colors because of the different pigments and they have in them,"},{"Start":"02:43.985 ","End":"02:49.530","Text":"those cones stimulate the retinal ganglion in different ways."},{"Start":"02:49.900 ","End":"02:57.450","Text":"The retinal ganglion can be contacted by several different cones."},{"Start":"02:57.450 ","End":"03:00.380","Text":"As you can see, this retinal ganglion would be"},{"Start":"03:00.380 ","End":"03:05.055","Text":"connected with actually all 3 different colors."},{"Start":"03:05.055 ","End":"03:12.950","Text":"What we get is actually 2 different colors that the retinal ganglion can see."},{"Start":"03:12.950 ","End":"03:15.070","Text":"It could be blue versus yellow,"},{"Start":"03:15.070 ","End":"03:16.550","Text":"that\u0027s what you\u0027ll see on the left."},{"Start":"03:16.550 ","End":"03:19.805","Text":"Red versus green, which is what we see in the center,"},{"Start":"03:19.805 ","End":"03:22.340","Text":"or black versus white,"},{"Start":"03:22.340 ","End":"03:26.120","Text":"depending on which cones are connected to them."},{"Start":"03:26.120 ","End":"03:32.290","Text":"The idea here is that 1 member of the color pair suppresses the other color."},{"Start":"03:32.290 ","End":"03:34.760","Text":"You get a signal,"},{"Start":"03:34.760 ","End":"03:39.740","Text":"let\u0027s say from a blue cone and that\u0027s going to suppress the green and red color."},{"Start":"03:39.740 ","End":"03:45.305","Text":"If one of them disappears,"},{"Start":"03:45.305 ","End":"03:48.890","Text":"then the brain interprets that as a downshift of"},{"Start":"03:48.890 ","End":"03:54.410","Text":"the opposite color and therefore you\u0027ll see the opposite color."},{"Start":"03:54.410 ","End":"03:58.895","Text":"That\u0027s pretty cool. If you go back to the previous slide and try this again,"},{"Start":"03:58.895 ","End":"04:01.735","Text":"maybe you\u0027ll be able to see it."},{"Start":"04:01.735 ","End":"04:05.045","Text":"How does the brain interpret what we see?"},{"Start":"04:05.045 ","End":"04:07.910","Text":"We will call that higher processing."},{"Start":"04:07.910 ","End":"04:11.870","Text":"Some visual information projects"},{"Start":"04:11.870 ","End":"04:15.110","Text":"through the optic nerves directly to the back of the brain."},{"Start":"04:15.110 ","End":"04:17.540","Text":"Here we see our eyes and we have"},{"Start":"04:17.540 ","End":"04:23.630","Text":"the optic nerves and you\u0027ll notice that in some places they cross over here,"},{"Start":"04:23.630 ","End":"04:25.190","Text":"there is an optic chiasm."},{"Start":"04:25.190 ","End":"04:27.860","Text":"We\u0027ll talk about that in a minute but in general,"},{"Start":"04:27.860 ","End":"04:32.090","Text":"what happens is that the signals go to the back of the brain to"},{"Start":"04:32.090 ","End":"04:39.215","Text":"an area that is called the right or left visual cortex."},{"Start":"04:39.215 ","End":"04:45.575","Text":"It travels through this optic chiasm at the base of the brain."},{"Start":"04:45.575 ","End":"04:49.310","Text":"This helps coordinate information spatially,"},{"Start":"04:49.310 ","End":"04:52.730","Text":"right and left, we see through 2 different eyes."},{"Start":"04:52.730 ","End":"04:56.510","Text":"What we see in each eye is not exactly the same."},{"Start":"04:56.510 ","End":"05:01.655","Text":"It\u0027s a binocular because we\u0027re not seeing them exactly from the same place."},{"Start":"05:01.655 ","End":"05:11.645","Text":"The optic nerves transmit the information to the brain where we can process it,"},{"Start":"05:11.645 ","End":"05:16.655","Text":"largely through the thalamus."},{"Start":"05:16.655 ","End":"05:19.820","Text":"You remember the thalamus is a routing station pretty much for"},{"Start":"05:19.820 ","End":"05:24.145","Text":"all sensory impulses except for smell, olfaction."},{"Start":"05:24.145 ","End":"05:27.260","Text":"You\u0027ll recall that from previous videos."},{"Start":"05:27.440 ","End":"05:32.345","Text":"Then the signals leave the thalamus and go"},{"Start":"05:32.345 ","End":"05:37.070","Text":"via this lateral geniculate nucleus the thalamus,"},{"Start":"05:37.070 ","End":"05:40.610","Text":"this area where there are lots of cells of"},{"Start":"05:40.610 ","End":"05:47.200","Text":"these sensory cells back into the right and left visual cortex is for processing."},{"Start":"05:47.200 ","End":"05:49.580","Text":"That\u0027s the original processing but then there\u0027s"},{"Start":"05:49.580 ","End":"05:53.899","Text":"a higher level of processing in 2 different,"},{"Start":"05:53.899 ","End":"05:55.385","Text":"what we call streams."},{"Start":"05:55.385 ","End":"06:03.305","Text":"There\u0027s the magnocellular and parvocellular that are in different parts of the brain."},{"Start":"06:03.305 ","End":"06:12.400","Text":"The magnocellular in a general sense it answers where did I see something?"},{"Start":"06:12.400 ","End":"06:15.455","Text":"Where did I see a particular image?"},{"Start":"06:15.455 ","End":"06:21.644","Text":"That\u0027ll be large fast and that doesn\u0027t give color information."},{"Start":"06:21.644 ","End":"06:24.080","Text":"On the other hand, the parvocellular,"},{"Start":"06:24.080 ","End":"06:28.690","Text":"the small cell pathway answers the question of what did I see?"},{"Start":"06:28.690 ","End":"06:32.270","Text":"This carries information about details,"},{"Start":"06:32.270 ","End":"06:33.615","Text":"about how small,"},{"Start":"06:33.615 ","End":"06:37.445","Text":"how slow and what the color was of what I saw."},{"Start":"06:37.445 ","End":"06:45.360","Text":"It\u0027s the integration of these two things that allows us to process an image."}],"ID":30031}],"Thumbnail":null,"ID":284108},{"Name":"Exercises","TopicPlaylistFirstVideoID":0,"Duration":null,"Videos":[{"Watched":false,"Name":"Exercise 1","Duration":"47s","ChapterTopicVideoID":28488,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.875","Text":"Where does perception occur?"},{"Start":"00:04.875 ","End":"00:06.825","Text":"Does it occur in the spinal cord,"},{"Start":"00:06.825 ","End":"00:09.750","Text":"the cerebral cortex, receptors,"},{"Start":"00:09.750 ","End":"00:11.325","Text":"or in the thalamus?"},{"Start":"00:11.325 ","End":"00:13.080","Text":"Perception."},{"Start":"00:13.080 ","End":"00:15.195","Text":"Well, let\u0027s see."},{"Start":"00:15.195 ","End":"00:19.050","Text":"It\u0027s clearly not in the spinal cord."},{"Start":"00:19.050 ","End":"00:20.820","Text":"We don\u0027t perceive things there."},{"Start":"00:20.820 ","End":"00:23.730","Text":"We don\u0027t perceive them in the receptors."},{"Start":"00:23.730 ","End":"00:26.730","Text":"We receive the signals there and certainly not in the thalamus."},{"Start":"00:26.730 ","End":"00:28.380","Text":"It\u0027s in the cerebral cortex."},{"Start":"00:28.380 ","End":"00:33.315","Text":"Remember, we get some stimulus which is received."},{"Start":"00:33.315 ","End":"00:37.545","Text":"Then there\u0027s some transduction which moves that stimulus"},{"Start":"00:37.545 ","End":"00:42.405","Text":"to a nerve cell and then it is perceived in the brain."},{"Start":"00:42.405 ","End":"00:47.160","Text":"Our answer is the cerebral cortex in the brain."}],"ID":29972},{"Watched":false,"Name":"Exercise 2","Duration":"58s","ChapterTopicVideoID":28489,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:09.442","Text":"If a person\u0027s cold receptors no longer convert cold stimuli into sensory signals,"},{"Start":"00:09.442 ","End":"00:13.425","Text":"that person has a problem with which process?"},{"Start":"00:13.425 ","End":"00:16.200","Text":"Is it reception, transmission, perception,"},{"Start":"00:16.200 ","End":"00:18.270","Text":"or transduction?"},{"Start":"00:18.270 ","End":"00:20.475","Text":"Well, let\u0027s see."},{"Start":"00:20.475 ","End":"00:25.230","Text":"We\u0027re clearly not talking about reception because the question x asks"},{"Start":"00:25.230 ","End":"00:30.105","Text":"the question about converting the cold stimuli into sensory signals."},{"Start":"00:30.105 ","End":"00:35.160","Text":"It\u0027s not the transmission because it\u0027s not the transmission through the nerves."},{"Start":"00:35.160 ","End":"00:36.570","Text":"It\u0027s not the perception,"},{"Start":"00:36.570 ","End":"00:38.760","Text":"that happens in the brain."},{"Start":"00:38.760 ","End":"00:41.010","Text":"It\u0027s got to be transduction."},{"Start":"00:41.010 ","End":"00:45.740","Text":"Remember, transduction is this process that occurs inside the cell,"},{"Start":"00:45.740 ","End":"00:54.230","Text":"which is between the signal being received by the receptor and the cell response."},{"Start":"00:54.230 ","End":"00:58.110","Text":"It\u0027s a signal transduction pathway."}],"ID":29973},{"Watched":false,"Name":"Exercise 3","Duration":"36s","ChapterTopicVideoID":28490,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.465","Text":"After somatosensory transduction."},{"Start":"00:03.465 ","End":"00:06.270","Text":"After transduction, the signal,"},{"Start":"00:06.270 ","End":"00:08.985","Text":"the sensory signal travels through"},{"Start":"00:08.985 ","End":"00:14.955","Text":"the brain and travels to the brain as what kind of a signal?"},{"Start":"00:14.955 ","End":"00:18.405","Text":"Well, it\u0027s got to be electrical because it goes through nerves, right?"},{"Start":"00:18.405 ","End":"00:20.040","Text":"It can\u0027t be pressure,"},{"Start":"00:20.040 ","End":"00:21.825","Text":"it can\u0027t be optical,"},{"Start":"00:21.825 ","End":"00:24.060","Text":"and it can\u0027t be thermal."},{"Start":"00:24.060 ","End":"00:26.595","Text":"It\u0027s got to be electrical."},{"Start":"00:26.595 ","End":"00:28.020","Text":"The stimulus, for instance,"},{"Start":"00:28.020 ","End":"00:29.820","Text":"comes to the skin."},{"Start":"00:29.820 ","End":"00:33.060","Text":"Here\u0027s a blowup of it and goes to the brain through"},{"Start":"00:33.060 ","End":"00:37.120","Text":"this electrical signal that goes through the nerves."}],"ID":29974},{"Watched":false,"Name":"Exercise 4","Duration":"1m 24s","ChapterTopicVideoID":28491,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.100","Text":"Many people experience motion sickness while traveling in a car."},{"Start":"00:05.100 ","End":"00:13.995","Text":"This sensation results from contradictory inputs that arise from which of these 2 senses?"},{"Start":"00:13.995 ","End":"00:20.280","Text":"Well, when you\u0027re in a car, clearly you\u0027re going to have your eyes open,"},{"Start":"00:20.280 ","End":"00:24.375","Text":"and you\u0027re going to be feeling how the car moves."},{"Start":"00:24.375 ","End":"00:29.219","Text":"Which of these are those feelings?"},{"Start":"00:29.219 ","End":"00:33.960","Text":"Is it proprioception and kinesthesia?"},{"Start":"00:33.960 ","End":"00:37.470","Text":"Is it somatosensation and equilibrium?"},{"Start":"00:37.470 ","End":"00:40.750","Text":"Gustation and vibration?"},{"Start":"00:40.750 ","End":"00:43.645","Text":"Or vision and the vestibular system?"},{"Start":"00:43.645 ","End":"00:48.315","Text":"Well, we said that it has to do with eyes clearly,"},{"Start":"00:48.315 ","End":"00:53.134","Text":"and you remember the vestibular system is the system that"},{"Start":"00:53.134 ","End":"00:59.265","Text":"we understand where we are in space and our movement through space."},{"Start":"00:59.265 ","End":"01:03.660","Text":"D is definitely going to be the answer."},{"Start":"01:03.760 ","End":"01:11.525","Text":"Clearly, it\u0027s D and you\u0027ll remember this static equilibrium,"},{"Start":"01:11.525 ","End":"01:20.880","Text":"which is what gives us this feeling of location in vestibular sensation."}],"ID":29975},{"Watched":false,"Name":"Exercise 5","Duration":"1m 45s","ChapterTopicVideoID":28492,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:09.150","Text":"Which of the following are found only in some kind of skin and detect skin deflection?"},{"Start":"00:09.150 ","End":"00:12.900","Text":"Skin deflection, so what does that going to mean?"},{"Start":"00:12.900 ","End":"00:16.905","Text":"It\u0027s going to mean that our skin is touched"},{"Start":"00:16.905 ","End":"00:21.885","Text":"lightly and displaced may be slightly but just touched lightly."},{"Start":"00:21.885 ","End":"00:24.195","Text":"Would it be Meissner\u0027s corpuscles,"},{"Start":"00:24.195 ","End":"00:28.950","Text":"Merkel\u0027s disks, would it be hair receptors or Krause end bulbs?"},{"Start":"00:28.950 ","End":"00:32.510","Text":"Let\u0027s remember what each of these things are."},{"Start":"00:32.510 ","End":"00:35.975","Text":"The Merkel\u0027s disks, if you remember,"},{"Start":"00:35.975 ","End":"00:38.150","Text":"are densely distributed, where?"},{"Start":"00:38.150 ","End":"00:43.190","Text":"In the fingertips, so that\u0027s an area which has a high density"},{"Start":"00:43.190 ","End":"00:49.245","Text":"and it responds to light touch,"},{"Start":"00:49.245 ","End":"00:50.945","Text":"that\u0027s important for us to remember."},{"Start":"00:50.945 ","End":"00:54.500","Text":"The Meissner corpuscles, on the other hand, yes,"},{"Start":"00:54.500 ","End":"00:57.500","Text":"are also found in the fingertips and so on but they"},{"Start":"00:57.500 ","End":"01:02.435","Text":"respond to fine touch and to pressure."},{"Start":"01:02.435 ","End":"01:04.760","Text":"It could be either of these 2,"},{"Start":"01:04.760 ","End":"01:08.585","Text":"but we\u0027re talking about the flexion so maybe it\u0027s this light touch."},{"Start":"01:08.585 ","End":"01:12.525","Text":"The Ruffini endings detect skin stretch,"},{"Start":"01:12.525 ","End":"01:14.115","Text":"we\u0027re not talking about stretch,"},{"Start":"01:14.115 ","End":"01:18.230","Text":"the Pacinian corpuscles sense deep pressure,"},{"Start":"01:18.230 ","End":"01:20.540","Text":"that\u0027s not what we\u0027re talking about"},{"Start":"01:20.540 ","End":"01:23.450","Text":"and these Krause end bulbs have something to do with temperature."},{"Start":"01:23.450 ","End":"01:25.295","Text":"We\u0027re not talking about that either."},{"Start":"01:25.295 ","End":"01:29.900","Text":"In that case, the answer is Merkel\u0027s disks,"},{"Start":"01:29.900 ","End":"01:33.285","Text":"which affect glabrous skin."},{"Start":"01:33.285 ","End":"01:35.975","Text":"Glabrous means that it has no hair."},{"Start":"01:35.975 ","End":"01:39.020","Text":"The other answers all had hairy so that"},{"Start":"01:39.020 ","End":"01:42.875","Text":"certainly means that we must be talking about Merkel\u0027s disk."},{"Start":"01:42.875 ","End":"01:45.030","Text":"That\u0027s the correct answer."}],"ID":29976},{"Watched":false,"Name":"Exercise 6","Duration":"1m 13s","ChapterTopicVideoID":28493,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.000","Text":"If you were to burn your epidermis,"},{"Start":"00:03.000 ","End":"00:04.680","Text":"that\u0027s the skin on the outside,"},{"Start":"00:04.680 ","End":"00:08.625","Text":"what receptor type would you most likely burn?"},{"Start":"00:08.625 ","End":"00:11.240","Text":"Free nerve endings, Ruffini endings,"},{"Start":"00:11.240 ","End":"00:13.880","Text":"Pacinian corpuscle, and hair receptors."},{"Start":"00:13.880 ","End":"00:17.085","Text":"We should go back to our figure."},{"Start":"00:17.085 ","End":"00:20.070","Text":"Remember what each of these things are."},{"Start":"00:20.070 ","End":"00:24.480","Text":"Remember the Merkel\u0027s discs and the Meissner\u0027s corpuscles,"},{"Start":"00:24.480 ","End":"00:27.420","Text":"the Ruffini endings, the Pacinian corpuscles,"},{"Start":"00:27.420 ","End":"00:29.880","Text":"and the Krause end bulbs."},{"Start":"00:29.880 ","End":"00:33.210","Text":"Our question then was,"},{"Start":"00:33.210 ","End":"00:35.895","Text":"which would you most likely burn?"},{"Start":"00:35.895 ","End":"00:38.790","Text":"The free nerve endings,"},{"Start":"00:38.790 ","End":"00:41.445","Text":"possibly the Ruffini endings."},{"Start":"00:41.445 ","End":"00:45.590","Text":"We\u0027re looking here for what would burn our epidermis,"},{"Start":"00:45.590 ","End":"00:48.530","Text":"the outside of the skin."},{"Start":"00:48.530 ","End":"00:54.145","Text":"We need something which is as close to the outside of the skin as possible."},{"Start":"00:54.145 ","End":"00:56.355","Text":"Let\u0027s look at our figure."},{"Start":"00:56.355 ","End":"01:02.120","Text":"As you can see, what\u0027s closest really to the skin,"},{"Start":"01:02.120 ","End":"01:03.150","Text":"to the epidermis,"},{"Start":"01:03.150 ","End":"01:07.445","Text":"the exterior of the skin are the free nerve endings."},{"Start":"01:07.445 ","End":"01:10.460","Text":"That\u0027s what our answer will be."},{"Start":"01:10.460 ","End":"01:13.380","Text":"Free nerve endings."}],"ID":29977},{"Watched":false,"Name":"Exercise 7","Duration":"1m 6s","ChapterTopicVideoID":28494,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.230","Text":"Many diabetic patients are warned by their doctors to test"},{"Start":"00:04.230 ","End":"00:09.640","Text":"their glucose levels by pricking the sides of their fingers,"},{"Start":"00:09.830 ","End":"00:12.135","Text":"rather than the pads,"},{"Start":"00:12.135 ","End":"00:15.750","Text":"that tops of the fingers or the bottoms of the fingers where you touch things."},{"Start":"00:15.750 ","End":"00:20.699","Text":"Pricking the sides avoids stimulating which receptor?"},{"Start":"00:20.699 ","End":"00:26.460","Text":"Again, we\u0027ve got these various parts of the dermis that are under"},{"Start":"00:26.460 ","End":"00:33.850","Text":"the skin and we want to know which of them we don\u0027t want to stimulate."},{"Start":"00:33.850 ","End":"00:38.220","Text":"Let\u0027s remember again what there is under the skin"},{"Start":"00:38.220 ","End":"00:43.485","Text":"that\u0027s close to the surface that we don\u0027t want to prick."},{"Start":"00:43.485 ","End":"00:45.650","Text":"The Merkel disks are up there."},{"Start":"00:45.650 ","End":"00:48.380","Text":"The Meissner corpuscles are up there,"},{"Start":"00:48.380 ","End":"00:51.050","Text":"other ones are lower."},{"Start":"00:51.050 ","End":"00:55.700","Text":"It\u0027s going to be 1 of those 2. Let\u0027s see."},{"Start":"00:55.700 ","End":"00:59.450","Text":"It\u0027s not going to be the Ruffini endings, those are deeper."},{"Start":"00:59.450 ","End":"01:01.850","Text":"The Nociceptors\u0027 really deep."},{"Start":"01:01.850 ","End":"01:05.940","Text":"It\u0027s got to be the Meissner corpuscles."}],"ID":29978},{"Watched":false,"Name":"Exercise 8","Duration":"1m 6s","ChapterTopicVideoID":28495,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.575","Text":"Which of the following has the most taste receptors?"},{"Start":"00:04.575 ","End":"00:08.250","Text":"We\u0027re talking about taste receptors here on the tongue."},{"Start":"00:08.250 ","End":"00:11.835","Text":"These are different papillae on the tongue, and we\u0027re asked,"},{"Start":"00:11.835 ","End":"00:18.045","Text":"which has the most taste receptors?"},{"Start":"00:18.045 ","End":"00:21.540","Text":"It\u0027s none, any of the first 3."},{"Start":"00:21.540 ","End":"00:23.910","Text":"It\u0027s the filiform papillae."},{"Start":"00:23.910 ","End":"00:31.410","Text":"If you remember, the filiform papillae that are on the surface of the tongue,"},{"Start":"00:31.410 ","End":"00:37.880","Text":"and the front of the tongue have no taste cells,"},{"Start":"00:37.880 ","End":"00:42.320","Text":"and they just help move the substances on the tongue."},{"Start":"00:42.320 ","End":"00:45.010","Text":"Fungiform contain 1-8,"},{"Start":"00:45.010 ","End":"00:48.285","Text":"the circumvallate have more,"},{"Start":"00:48.285 ","End":"00:53.000","Text":"but the foliate papillae that are located in the folds along"},{"Start":"00:53.000 ","End":"00:59.640","Text":"the edges here contain many taste buds within their folds."},{"Start":"00:59.640 ","End":"01:06.930","Text":"Those are the ones that have the most taste receptors."}],"ID":29979},{"Watched":false,"Name":"Exercise 9","Duration":"44s","ChapterTopicVideoID":28496,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:07.470","Text":"How many different taste molecules do taste cells each detect?"},{"Start":"00:07.470 ","End":"00:12.705","Text":"We\u0027re talking about each cell and how many each of them can detect."},{"Start":"00:12.705 ","End":"00:17.430","Text":"1, 5, 10 or does it depend on the spot on the tongue?"},{"Start":"00:17.430 ","End":"00:21.700","Text":"This we have to remember, it\u0027s 1."},{"Start":"00:21.830 ","End":"00:30.000","Text":"Remember this figure in which in humans there are 5 primary tastes,"},{"Start":"00:30.000 ","End":"00:40.325","Text":"but each taste has only 1 corresponding receptor, that is cell."},{"Start":"00:40.325 ","End":"00:44.610","Text":"The answer for this is going to be 1."}],"ID":29980},{"Watched":false,"Name":"Exercise 10","Duration":"1m 4s","ChapterTopicVideoID":28497,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.505","Text":"Salty foods activate the taste cells, how?"},{"Start":"00:05.505 ","End":"00:08.370","Text":"By exciting the taste directly,"},{"Start":"00:08.370 ","End":"00:10.440","Text":"the taste cell salt."},{"Start":"00:10.440 ","End":"00:15.120","Text":"Exciting the taste cell directly by causing hydrogen ions to enter the cell,"},{"Start":"00:15.120 ","End":"00:18.750","Text":"by causing sodium ions or sodium channels to close,"},{"Start":"00:18.750 ","End":"00:24.345","Text":"by binding directly to the receptors, salty foods."},{"Start":"00:24.345 ","End":"00:27.480","Text":"This we just need to remember, actually,"},{"Start":"00:27.480 ","End":"00:32.430","Text":"it\u0027s going to be exciting the taste cell directly."},{"Start":"00:32.430 ","End":"00:37.110","Text":"If you remember, salty taste then provides sodium ions"},{"Start":"00:37.110 ","End":"00:42.495","Text":"that enter the taste neurons and excite them directly because,"},{"Start":"00:42.495 ","End":"00:46.190","Text":"if you remember, it\u0027s the sodium channels which"},{"Start":"00:46.190 ","End":"00:50.975","Text":"change the polarization of the cell of nerve cells."},{"Start":"00:50.975 ","End":"00:54.500","Text":"In this case, it\u0027s the sodium ions from the salt that"},{"Start":"00:54.500 ","End":"00:58.340","Text":"enter the taste neurons directly and excite them."},{"Start":"00:58.340 ","End":"01:04.860","Text":"The answer to our question is going to be exciting the taste cell directly."}],"ID":29981},{"Watched":false,"Name":"Exercise 11","Duration":"1m 32s","ChapterTopicVideoID":28498,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:03.675","Text":"All sensory signals except,"},{"Start":"00:03.675 ","End":"00:05.970","Text":"which of these,"},{"Start":"00:05.970 ","End":"00:09.570","Text":"except traveled to the, what?"},{"Start":"00:09.570 ","End":"00:13.470","Text":"In the brain before the cerebral cortex."},{"Start":"00:13.470 ","End":"00:15.440","Text":"Now notice in to the what,"},{"Start":"00:15.440 ","End":"00:16.530","Text":"we\u0027ve got 2 choices."},{"Start":"00:16.530 ","End":"00:20.115","Text":"We\u0027ve got thalamus or cranial nerves."},{"Start":"00:20.115 ","End":"00:25.250","Text":"All sensory signals except which of these travel to"},{"Start":"00:25.250 ","End":"00:31.805","Text":"the thalamus or cranial nerves in the brain before the cerebral cortex."},{"Start":"00:31.805 ","End":"00:33.575","Text":"Well, let\u0027s see."},{"Start":"00:33.575 ","End":"00:37.355","Text":"It\u0027s going to be thalamus, if you remember,"},{"Start":"00:37.355 ","End":"00:44.390","Text":"because that\u0027s a place that almost all sensory signals go through."},{"Start":"00:44.390 ","End":"00:46.055","Text":"What\u0027s the exception?"},{"Start":"00:46.055 ","End":"00:48.175","Text":"Well, it\u0027s smell,"},{"Start":"00:48.175 ","End":"00:50.760","Text":"it\u0027s olfaction, if you remember,"},{"Start":"00:50.760 ","End":"00:52.820","Text":"so we\u0027ll cross off the other ones."},{"Start":"00:52.820 ","End":"00:56.360","Text":"I\u0027ll remind you with these 2 figures, in the thalamus,"},{"Start":"00:56.360 ","End":"01:01.174","Text":"here, the taste sensations go through the thalamus."},{"Start":"01:01.174 ","End":"01:04.510","Text":"That\u0027s going to be the answer."},{"Start":"01:04.510 ","End":"01:08.360","Text":"In the case of vision, as you can see,"},{"Start":"01:08.360 ","End":"01:17.820","Text":"there is also the nucleus of the thalamus here through which the vision usually goes."},{"Start":"01:17.820 ","End":"01:24.020","Text":"Therefore, our answer is going to be that all sensory signals except olfaction,"},{"Start":"01:24.020 ","End":"01:30.150","Text":"traveled to the thalamus in the brain before the cerebral cortex."}],"ID":29982},{"Watched":false,"Name":"Exercise 12","Duration":"1m 23s","ChapterTopicVideoID":28499,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.190","Text":"How is the ability to recognize the umami taste?"},{"Start":"00:05.190 ","End":"00:08.415","Text":"The umami taste. It\u0027s one of the tastes like a salty taste."},{"Start":"00:08.415 ","End":"00:10.935","Text":"How is that an evolutionary advantage?"},{"Start":"00:10.935 ","End":"00:14.655","Text":"It identifies healthy foods that are low in salt and sugar."},{"Start":"00:14.655 ","End":"00:17.775","Text":"It enhances the flavor of bland foods."},{"Start":"00:17.775 ","End":"00:22.455","Text":"It identifies foods that might contain essential amino acids."},{"Start":"00:22.455 ","End":"00:26.100","Text":"What does that mean? Amino acids, remember protein."},{"Start":"00:26.100 ","End":"00:30.750","Text":"It identifies foods that help maintain electrolyte balance."},{"Start":"00:30.750 ","End":"00:33.435","Text":"Well, so let\u0027s see."},{"Start":"00:33.435 ","End":"00:38.745","Text":"It\u0027s has nothing to do with salt and sugar."},{"Start":"00:38.745 ","End":"00:41.370","Text":"It has nothing to do with bland foods."},{"Start":"00:41.370 ","End":"00:44.450","Text":"It does have to do however, with proteins."},{"Start":"00:44.450 ","End":"00:48.445","Text":"If remember, the umami substances in food,"},{"Start":"00:48.445 ","End":"00:50.060","Text":"in this figure over here,"},{"Start":"00:50.060 ","End":"00:53.930","Text":"the primary tastes detected by humans are these sweet,"},{"Start":"00:53.930 ","End":"00:56.900","Text":"sour, bitter, salty, and umami."},{"Start":"00:56.900 ","End":"01:03.440","Text":"The umami receptors typically respond to glutamates."},{"Start":"01:03.440 ","End":"01:07.610","Text":"Glutamates, glutamates, all these are glutamates."},{"Start":"01:07.610 ","End":"01:10.280","Text":"What\u0027s in common with all of those things?"},{"Start":"01:10.280 ","End":"01:13.940","Text":"They all are foods that tend to be high in protein."},{"Start":"01:13.940 ","End":"01:17.780","Text":"So our answer then is going to be C. Umami"},{"Start":"01:17.780 ","End":"01:22.770","Text":"identifies foods that might contain essential amino acids."}],"ID":29983},{"Watched":false,"Name":"Exercise 13","Duration":"1m 17s","ChapterTopicVideoID":28500,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:08.055","Text":"In sound, pitch is measured in what of these different units,"},{"Start":"00:08.055 ","End":"00:12.705","Text":"and volume is measured in which of these units?"},{"Start":"00:12.705 ","End":"00:15.270","Text":"Well, if you remember, volume,"},{"Start":"00:15.270 ","End":"00:18.975","Text":"how loud things are certainly measured in decibels."},{"Start":"00:18.975 ","End":"00:22.560","Text":"Here\u0027s decibels and decibels."},{"Start":"00:22.560 ","End":"00:26.880","Text":"In sound, pitch is measured,"},{"Start":"00:26.880 ","End":"00:33.060","Text":"is it going to be by nanometers or is it going to be hertz?"},{"Start":"00:33.060 ","End":"00:36.810","Text":"Well, what I remember is that it\u0027s hertz."},{"Start":"00:36.810 ","End":"00:41.700","Text":"Our answer is going to be d. Let\u0027s see if that\u0027s right."},{"Start":"00:41.700 ","End":"00:45.275","Text":"Well, sure enough, here it is."},{"Start":"00:45.275 ","End":"00:49.745","Text":"Remember, decibels are the amplitude of the wave,"},{"Start":"00:49.745 ","End":"00:52.670","Text":"so that\u0027s how loud something is."},{"Start":"00:52.670 ","End":"00:57.875","Text":"High amplitude is loud sound and measured in decibels and the frequency of sounds."},{"Start":"00:57.875 ","End":"01:00.180","Text":"Remember that the pitches which humans can hear,"},{"Start":"01:00.940 ","End":"01:08.190","Text":"the frequencies which humans can hear are in a particular auditory field,"},{"Start":"01:08.190 ","End":"01:11.500","Text":"and that is measured in hertz."},{"Start":"01:11.500 ","End":"01:16.750","Text":"Hertz and decibels are our answers."}],"ID":29984},{"Watched":false,"Name":"Exercise 14","Duration":"59s","ChapterTopicVideoID":28501,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.805","Text":"Auditory hair cells are indirectly anchored where?"},{"Start":"00:05.805 ","End":"00:08.250","Text":"Are they in the basilar membrane,"},{"Start":"00:08.250 ","End":"00:11.220","Text":"oval window, tectorial membrane,"},{"Start":"00:11.220 ","End":"00:13.020","Text":"or in the ossicles?"},{"Start":"00:13.020 ","End":"00:15.806","Text":"Well, we\u0027re talking here about hearing, yes,"},{"Start":"00:15.806 ","End":"00:19.275","Text":"and they are indirectly anchored where?"},{"Start":"00:19.275 ","End":"00:25.245","Text":"Well, let\u0027s remember what this looked like."},{"Start":"00:25.245 ","End":"00:27.735","Text":"If you remember, there is"},{"Start":"00:27.735 ","End":"00:34.080","Text":"the basilar membrane and connected toward are the supporting cells and to them,"},{"Start":"00:34.080 ","End":"00:37.590","Text":"there are hair cells that are attached."},{"Start":"00:37.590 ","End":"00:42.730","Text":"The answer then is going to be the basilar membrane because"},{"Start":"00:42.730 ","End":"00:49.028","Text":"the basilar membrane has supporting cells which are indirectly,"},{"Start":"00:49.028 ","End":"00:52.226","Text":"they are bound to the hair cells,"},{"Start":"00:52.226 ","End":"00:56.510","Text":"so the hair cells are indirectly bound therefore to the basilar membrane."},{"Start":"00:56.510 ","End":"00:59.430","Text":"Our answer is going to be a."}],"ID":29985},{"Watched":false,"Name":"Exercise 15","Duration":"1m 5s","ChapterTopicVideoID":28502,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:04.275","Text":"Which of the following are found both in the auditory system,"},{"Start":"00:04.275 ","End":"00:05.940","Text":"the hearing system, yes,"},{"Start":"00:05.940 ","End":"00:07.560","Text":"and the vestibular system?"},{"Start":"00:07.560 ","End":"00:10.500","Text":"Remember, the vestibular system is a system that helps us"},{"Start":"00:10.500 ","End":"00:14.685","Text":"understand where we are in space."},{"Start":"00:14.685 ","End":"00:19.575","Text":"Which of the following are found in both auditory system and the vestibular system?"},{"Start":"00:19.575 ","End":"00:22.335","Text":"Is it the basilar membrane, hair cells,"},{"Start":"00:22.335 ","End":"00:26.340","Text":"semicircular canals, or ossicles?"},{"Start":"00:26.340 ","End":"00:29.190","Text":"We have to remember what each of these is."},{"Start":"00:29.190 ","End":"00:31.380","Text":"It\u0027s not going to be the basilar membrane."},{"Start":"00:31.380 ","End":"00:32.570","Text":"That, if you remember,"},{"Start":"00:32.570 ","End":"00:35.180","Text":"we found really in the auditory system."},{"Start":"00:35.180 ","End":"00:42.350","Text":"The semicircular canals we find in the vestibular system are the ossicles."},{"Start":"00:42.350 ","End":"00:44.785","Text":"It\u0027s the hair cells."},{"Start":"00:44.785 ","End":"00:50.420","Text":"Here, again are the hair cells that are found in the auditory system."},{"Start":"00:50.420 ","End":"00:56.300","Text":"Here are the hair cells that are found in the vestibular system."},{"Start":"00:56.300 ","End":"00:59.390","Text":"Our answer is going to be B,"},{"Start":"00:59.390 ","End":"01:00.470","Text":"the hair cells,"},{"Start":"01:00.470 ","End":"01:05.790","Text":"that are found both in the auditory system and the vestibular system."}],"ID":29986},{"Watched":false,"Name":"Exercise 16","Duration":"2m 20s","ChapterTopicVideoID":28503,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.020 ","End":"00:05.280","Text":"In this question, we\u0027re going to be talking about a particular disorder"},{"Start":"00:05.280 ","End":"00:10.890","Text":"called benign paroxysmal positional vertigo."},{"Start":"00:10.890 ","End":"00:15.150","Text":"This disorder is where some of the calcium carbonate crystals in"},{"Start":"00:15.150 ","End":"00:19.305","Text":"the utricle migrate into the semicircular canals."},{"Start":"00:19.305 ","End":"00:22.455","Text":"Why does this condition cause periods of dizziness?"},{"Start":"00:22.455 ","End":"00:29.655","Text":"Well, we have to remember what the utricle is."},{"Start":"00:29.655 ","End":"00:33.180","Text":"What happens, what are the crystals that are in them,"},{"Start":"00:33.180 ","End":"00:34.755","Text":"and what do they give us?"},{"Start":"00:34.755 ","End":"00:37.665","Text":"They\u0027re in the semicircular canals."},{"Start":"00:37.665 ","End":"00:40.680","Text":"Why would this cause dizziness?"},{"Start":"00:40.680 ","End":"00:42.320","Text":"In dizziness, of course,"},{"Start":"00:42.320 ","End":"00:46.820","Text":"we\u0027re going to have a vestibular problem in which we\u0027re not going to"},{"Start":"00:46.820 ","End":"00:51.865","Text":"understand exactly the position that we\u0027re in or that we\u0027re moving."},{"Start":"00:51.865 ","End":"00:55.100","Text":"In this condition, is it that the hair cells and"},{"Start":"00:55.100 ","End":"00:58.160","Text":"the semicircular canals will be constantly activated?"},{"Start":"00:58.160 ","End":"01:00.410","Text":"Remember, what we\u0027re asking here is"},{"Start":"01:00.410 ","End":"01:07.460","Text":"that some of these calcium carbonate crystals migrate into the semicircular canals."},{"Start":"01:07.460 ","End":"01:11.315","Text":"The hair cells in the semicircular canals will be constantly activated."},{"Start":"01:11.315 ","End":"01:16.295","Text":"The hair cells in the semicircular canals will now be stimulated by gravity."},{"Start":"01:16.295 ","End":"01:20.060","Text":"Remember what the calcium carbonate crystals do."},{"Start":"01:20.060 ","End":"01:23.060","Text":"The utricle no longer recognize acceleration."},{"Start":"01:23.060 ","End":"01:28.200","Text":"There\u0027ll be too much volume in the semicircular canals for them to detect motion."},{"Start":"01:28.250 ","End":"01:32.635","Text":"It\u0027s not the first, they\u0027re not constantly activated."},{"Start":"01:32.635 ","End":"01:37.085","Text":"Clearly, only some of them we were asked here."},{"Start":"01:37.085 ","End":"01:40.400","Text":"Yes, some of them migrate."},{"Start":"01:40.400 ","End":"01:45.140","Text":"The utricle will still be able to recognize acceleration and it\u0027s not"},{"Start":"01:45.140 ","End":"01:49.565","Text":"that too much of the volume in the semicircular canals."},{"Start":"01:49.565 ","End":"01:53.435","Text":"There\u0027ll be too much in the volume there to detect motion, if you remember,"},{"Start":"01:53.435 ","End":"01:58.790","Text":"that these crystals change or move in"},{"Start":"01:58.790 ","End":"02:05.305","Text":"a particular direction relative to the way the head is positioned."},{"Start":"02:05.305 ","End":"02:10.010","Text":"The hair cells in the semicircular canals will now be stimulated by"},{"Start":"02:10.010 ","End":"02:15.260","Text":"gravity because we\u0027d now have those crystals in the canals."},{"Start":"02:15.260 ","End":"02:19.950","Text":"So B is going to be our answer."}],"ID":29987},{"Watched":false,"Name":"Exercise 17","Duration":"1m 30s","ChapterTopicVideoID":28504,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.050 ","End":"00:05.655","Text":"Why do people over 55 often need reading glasses?"},{"Start":"00:05.655 ","End":"00:12.615","Text":"Remember, this has something to do with how the lens is not as flexible in older people."},{"Start":"00:12.615 ","End":"00:15.570","Text":"Their cornea no longer focuses correctly."},{"Start":"00:15.570 ","End":"00:18.990","Text":"Their lens no longer focuses correctly."},{"Start":"00:18.990 ","End":"00:23.160","Text":"Well, that makes sense. Remember, the lens is the one that got stiff."},{"Start":"00:23.160 ","End":"00:25.200","Text":"Their eyeball has elongated with age,"},{"Start":"00:25.200 ","End":"00:28.455","Text":"causing images to focus in front of their retina."},{"Start":"00:28.455 ","End":"00:33.240","Text":"Well, reading glasses means that we\u0027re going to be seeing"},{"Start":"00:33.240 ","End":"00:39.380","Text":"things clearly in the distance and not close-up."},{"Start":"00:39.380 ","End":"00:44.420","Text":"You will remember, soon, we\u0027ll see the image that will remind you that"},{"Start":"00:44.420 ","End":"00:48.740","Text":"the problem is that older people can\u0027t focus on their retina."},{"Start":"00:48.740 ","End":"00:51.655","Text":"Instead, they focus behind the retina, not in front."},{"Start":"00:51.655 ","End":"00:53.540","Text":"Their retina has thinned with age,"},{"Start":"00:53.540 ","End":"00:54.800","Text":"making vision more difficult."},{"Start":"00:54.800 ","End":"00:57.970","Text":"Well, that\u0027s not the issue that we\u0027re talking about here."},{"Start":"00:57.970 ","End":"01:00.885","Text":"Let\u0027s see. It\u0027s not the first,"},{"Start":"01:00.885 ","End":"01:02.880","Text":"it\u0027s not the third,"},{"Start":"01:02.880 ","End":"01:04.725","Text":"and it\u0027s not the fourth."},{"Start":"01:04.725 ","End":"01:08.265","Text":"The lens can\u0027t focus correctly."},{"Start":"01:08.265 ","End":"01:12.035","Text":"What we usually get is presbyopia,"},{"Start":"01:12.035 ","End":"01:18.155","Text":"which means that the focus is beyond the retina and that occurs with age."},{"Start":"01:18.155 ","End":"01:19.939","Text":"We have the loss of flexibility."},{"Start":"01:19.939 ","End":"01:23.150","Text":"The lens and the images in a distance are clear,"},{"Start":"01:23.150 ","End":"01:25.850","Text":"but the images nearby are blurry."},{"Start":"01:25.850 ","End":"01:30.120","Text":"That\u0027s why the third answer was wrong."}],"ID":29988},{"Watched":false,"Name":"Exercise 18","Duration":"1m 47s","ChapterTopicVideoID":28505,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:06.695","Text":"Why is it easier to see images at night using peripheral rather than central vision?"},{"Start":"00:06.695 ","End":"00:09.840","Text":"Remember there were rods and cones."},{"Start":"00:09.840 ","End":"00:13.170","Text":"You remember that it was the cones that gave us"},{"Start":"00:13.170 ","End":"00:16.200","Text":"the detailed vision in the center of our eye,"},{"Start":"00:16.200 ","End":"00:19.530","Text":"and the rods were more on the periphery."},{"Start":"00:19.530 ","End":"00:23.820","Text":"Why is it easier to see images at night using peripheral vision?"},{"Start":"00:23.820 ","End":"00:28.455","Text":"Remember, they require less light. Let\u0027s see."},{"Start":"00:28.455 ","End":"00:29.895","Text":"Remembering those things,"},{"Start":"00:29.895 ","End":"00:31.530","Text":"let\u0027s look at these answers."},{"Start":"00:31.530 ","End":"00:35.340","Text":"Cones are denser in the periphery of the retina. That\u0027s wrong."},{"Start":"00:35.340 ","End":"00:39.690","Text":"The cones are denser in the center of the retina."},{"Start":"00:39.690 ","End":"00:44.660","Text":"Let\u0027s get rid of that. Bipolar cells are denser in the periphery of the retina."},{"Start":"00:44.660 ","End":"00:46.920","Text":"Well, that\u0027s not true either."},{"Start":"00:46.920 ","End":"00:49.570","Text":"Let\u0027s get rid of that."},{"Start":"00:49.570 ","End":"00:53.300","Text":"Rods are denser in the periphery of the retina."},{"Start":"00:53.300 ","End":"00:57.350","Text":"Well, yes, rods are the ones that we\u0027re seeing images at night."},{"Start":"00:57.350 ","End":"01:00.110","Text":"We don\u0027t have any rods really in the center of our retina,"},{"Start":"01:00.110 ","End":"01:01.985","Text":"so that looks like it could be right."},{"Start":"01:01.985 ","End":"01:05.840","Text":"D, the optic nerve exits at the periphery of the retina."},{"Start":"01:05.840 ","End":"01:09.165","Text":"Well, that\u0027s pretty irrelevant even if it were true."},{"Start":"01:09.165 ","End":"01:13.220","Text":"Clearly, the answer is that in peripheral vision,"},{"Start":"01:13.220 ","End":"01:19.810","Text":"remember we see things that are on the sides of our direct vision area."},{"Start":"01:19.810 ","End":"01:23.265","Text":"In those, we have,"},{"Start":"01:23.265 ","End":"01:29.050","Text":"the vision is produced by rods which are located at the retina edges."},{"Start":"01:29.050 ","End":"01:31.820","Text":"That\u0027s going to be our answer."},{"Start":"01:31.820 ","End":"01:36.230","Text":"Remembering that peripheral vision is not as sharp as a central vision,"},{"Start":"01:36.230 ","End":"01:39.760","Text":"but it is more sensitive to light and motion."},{"Start":"01:39.760 ","End":"01:46.320","Text":"Our answer is going to be that rods are denser in the periphery of the retina."}],"ID":29989},{"Watched":false,"Name":"Exercise 19","Duration":"47s","ChapterTopicVideoID":28486,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:05.100","Text":"A person catching a ball must coordinates her head and eyes."},{"Start":"00:05.100 ","End":"00:09.195","Text":"What part of the brain is helping her to do this?"},{"Start":"00:09.195 ","End":"00:13.500","Text":"That\u0027s coordination between her head and eyes."},{"Start":"00:13.500 ","End":"00:15.855","Text":"Her head, so that\u0027s going to be vestibular things,"},{"Start":"00:15.855 ","End":"00:19.200","Text":"and her eyes, that\u0027s what her vision."},{"Start":"00:19.200 ","End":"00:23.835","Text":"So which of these must they coordinate?"},{"Start":"00:23.835 ","End":"00:26.565","Text":"Well, is it going to be hypothalamus, pineal gland,"},{"Start":"00:26.565 ","End":"00:29.880","Text":"thalamus, or superior colliculus?"},{"Start":"00:29.880 ","End":"00:33.960","Text":"Well, this is something we just have to know in order to get the correct answer."},{"Start":"00:33.960 ","End":"00:36.120","Text":"It\u0027s not any of the first 3,"},{"Start":"00:36.120 ","End":"00:39.315","Text":"it is the superior colliculus."},{"Start":"00:39.315 ","End":"00:43.790","Text":"This is actually a question that we didn\u0027t cover in our videos,"},{"Start":"00:43.790 ","End":"00:48.030","Text":"but it\u0027s something that you might want to learn on your own."}],"ID":29990},{"Watched":false,"Name":"Exercise 20","Duration":"1m 19s","ChapterTopicVideoID":28487,"CourseChapterTopicPlaylistID":284109,"HasSubtitles":true,"ThumbnailPath":null,"UploadDate":null,"DurationForVideoObject":null,"Description":null,"MetaTitle":null,"MetaDescription":null,"Canonical":null,"VideoComments":[],"Subtitles":[{"Start":"00:00.000 ","End":"00:02.880","Text":"The satellite is launched into space,"},{"Start":"00:02.880 ","End":"00:06.855","Text":"but explodes after exiting the Earth\u0027s atmosphere."},{"Start":"00:06.855 ","End":"00:09.690","Text":"It has exited the earth\u0027s atmosphere."},{"Start":"00:09.690 ","End":"00:12.840","Text":"Which statement accurately reflects the observations"},{"Start":"00:12.840 ","End":"00:16.665","Text":"made by an astronaut on a spacewalk,"},{"Start":"00:16.665 ","End":"00:19.695","Text":"he\u0027s out there outside the Earth\u0027s atmosphere,"},{"Start":"00:19.695 ","End":"00:23.565","Text":"outside the International Space Station during the explosion?"},{"Start":"00:23.565 ","End":"00:27.900","Text":"Would the astronauts see the explosion but not hear it?"},{"Start":"00:27.900 ","End":"00:30.120","Text":"The astronaut will not sense the explosion,"},{"Start":"00:30.120 ","End":"00:33.284","Text":"the astronaut will see the explosion and then hear the boom?"},{"Start":"00:33.284 ","End":"00:37.455","Text":"The astronaut will feel the concussive force of the explosion,"},{"Start":"00:37.455 ","End":"00:39.330","Text":"but will not see it."},{"Start":"00:39.330 ","End":"00:41.880","Text":"This is a question about sound, really."},{"Start":"00:41.880 ","End":"00:46.355","Text":"If you remember, sound has to go through a medium."},{"Start":"00:46.355 ","End":"00:50.000","Text":"Yes. The answer is that the astronaut would see"},{"Start":"00:50.000 ","End":"00:53.900","Text":"the explosion but would not hear a boom. Why is that?"},{"Start":"00:53.900 ","End":"01:00.410","Text":"Because sound waves are mechanical pressure waves that move through a medium."},{"Start":"01:00.410 ","End":"01:02.536","Text":"We\u0027re more outside the Earth\u0027s atmosphere,"},{"Start":"01:02.536 ","End":"01:03.938","Text":"we have no medium,"},{"Start":"01:03.938 ","End":"01:06.110","Text":"such as air or water."},{"Start":"01:06.110 ","End":"01:08.990","Text":"Therefore, the astronaut would see the explosion,"},{"Start":"01:08.990 ","End":"01:10.400","Text":"he\u0027d had no trouble seeing it,"},{"Start":"01:10.400 ","End":"01:13.670","Text":"but he wouldn\u0027t hear or feel anything because there\u0027s"},{"Start":"01:13.670 ","End":"01:19.290","Text":"no medium through which the shock waves or the sound waves would go."}],"ID":29991}],"Thumbnail":null,"ID":284109}]

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