| 00:00 | this is this is Elektra, 22 neuroscience, and we continuing talking about |
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| 00:05 | auditory system. And so we discussed anatomy of the inner, the middle |
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| 00:11 | the external air, the external ears a pen and the air canal or |
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| 00:17 | auditorium. Mediators are located in the of years, where you have the |
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| 00:21 | drum, the auditory obstacles that are the oval window and in the inner |
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| 00:26 | you have, of course, the of the cochlea, which is a |
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| 00:30 | of the vestibular cochlea apparatus, and outputs from the cochlear will produce the |
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| 00:35 | portion of this tubular cochlear cranial Eight. Aziz. We discuss the |
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| 00:42 | that sound vibrations, the movement of air molecules and these waves. They're |
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| 00:47 | to come into the external auditory mediators then is going to vibrate the ear |
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| 00:52 | . The ear drum is connected to three obstacles. The values increase in |
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| 00:57 | peas and with increased torque and connectivity these also calls the drum movement, |
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| 01:04 | vibrations could be exaggerated, even to move the oval window that is |
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| 01:10 | onto the cochlea in a year. you were to take the cochlea shown |
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| 01:17 | all looks like a snail. It's the size of a pea. And |
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| 01:22 | you were thio on coil the cochlea would see a certain structure. You |
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| 01:30 | see the Scalia, the stimuli on scholar, the stimulant off Scallon Media |
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| 01:35 | will contain the organ of Corti, hearing of Perata's and the Scalia timpani |
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| 01:41 | the bottom which will contain the round . Now the three chambers have filled |
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| 01:47 | fluid, and the middle chamber will the hair cells, which are the |
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| 01:52 | receptors. And they will trans the mechanical movement of the fluid and |
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| 01:58 | pictorial number into which they're connected into electrochemical signals. Eso you have here |
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| 02:06 | base basically off the cochlea and all all the way to the hillock, |
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| 02:10 | tree MMA and the apex. You see all three of these. Flu |
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| 02:14 | filled chambers. If you look at fluid that is actually contained in these |
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| 02:21 | , the stimuli and the timpani they Paralympic Paralympic is very similar. |
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| 02:28 | What we know is our cerebrospinal which is typically low and and potassium |
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| 02:37 | the outside of the cells and high sodium. So remember that super spinal |
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| 02:43 | is high and sodium on the sodium chloride and then the inside. |
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| 02:50 | is high in potassium, but on outside of Sloan potassium, the seven |
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| 02:53 | Mueller typical in CSF extra cellular, see potassium, about $3.5 million |
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| 03:02 | Enderlin, however, has very high concentrations, in fact, and the |
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| 03:08 | has 150 million Mueller. Concentration of and low sodium transportation. Low sodium |
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| 03:20 | of one million Moloch on dso This this Grady In this, uh, |
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| 03:27 | in off high potassium, there's established active transport the three of us secularist |
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| 03:36 | the filial cells that are producing a , and and transporting a lot of |
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| 03:41 | potassium into the end, a And so the signaling, an activation |
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| 03:46 | the hair sauce is going to be through. Potassium in flex is supposed |
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| 03:51 | look classical, we've learned, and sodium regulation of sodium influx, even |
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| 03:56 | the level of the photo receptors where regulating the influx of sodium moving on |
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| 04:04 | , just like in written. And you recall, we talked about retina |
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| 04:08 | map the retina topic map. We Thio point by point representation. There |
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| 04:14 | a point in the visual field that is represented by receptive fields in the |
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| 04:21 | . That point is represented in the funicular nucleus of the columnist on that |
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| 04:26 | is represented all the way to the visual cortex. In cochlear, you |
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| 04:31 | a tono topic map. In this , it's the map that basically has |
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| 04:38 | tones on it. The base off cochlea and the hair cells that are |
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| 04:46 | at the base of the cochlear are sensitive and processing high frequency sounds. |
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| 04:52 | as you move toward that, apex, this basilar membrane. As |
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| 04:59 | can see, this basilar membrane itself , and it becomes mawr floppy soon |
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| 05:06 | speak. And as it changes its shape, the cells that air hair |
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| 05:13 | that are connected to the territorial to bazaar learned the tutorial membranes well into |
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| 05:18 | bezel number in particular will be processing frequency sounds. And so the analogy |
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| 05:26 | I'd like to give and unfortunately, don't have a good demonstration. But |
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| 05:32 | this may were the analogy that I'd to give is a gymnasts ribbon when |
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| 05:38 | move something really fast this Imagine the to my hand is the dazzle, |
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| 05:46 | membrane of processes, high frequencies, you can see that the higher frequency |
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| 05:52 | move the fastest moves. Look what when the membrane becomes looser. It's |
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| 05:59 | necessarily the exact structure toward this other . What's happening now? Now you |
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| 06:05 | see processing a very fast vibrations by cloth, very close to the hand |
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| 06:11 | much slower fluttering toward what would be apex or the helicopter Prima off the |
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| 06:20 | . Okay, so imagine this as . Use an example of gymnasts ribbon |
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| 06:26 | journalists are moving the rivers that you're really fast, very close Thio where |
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| 06:32 | hand is holding the river. And what happens that where the end of |
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| 06:37 | ribbons is flowing very slow, making wide waves. Okay, so this |
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| 06:43 | basically a frequency and coding, and cells along different extend from the base |
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| 06:49 | the cochlea to the apex will be and most being be most responsive. |
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| 06:58 | certain frequencies of sound. So the of sound let's talk about it. |
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| 07:05 | there you have the stay bees that's the oval window. So these little |
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| 07:11 | that are moving the oval window. movement of that oval window is moving |
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| 07:16 | fluid filled chamber and the moving the , and that movement of the fluid |
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| 07:22 | into the movement after dazzler membrane. as the fluid moves, the Basel |
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| 07:30 | membrane displaces. So what you have the organ of Corti or the the |
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| 07:38 | organ is you have two very important . You have the tech Torrey Aled |
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| 07:44 | or the roof Okay, the tech Allnut brain and the textile or |
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| 07:50 | Now rain is connected to the Off the hair cells, you have |
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| 07:58 | rows of outer hair cells and one off inner hair cells that are located |
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| 08:06 | over the inside, uh, middle . So as you can see when |
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| 08:13 | a movement of the fluid, this membrane on which the organ, of |
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| 08:19 | he's sitting and you have the supporting that are supporting that sitting here in |
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| 08:23 | supporting the hair cells, then the . The basilar membrane moves, and |
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| 08:30 | happens is because the dictatorial membrane is to the silly on the hair |
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| 08:35 | It's just sicilia into the direction. left to right, it bends the |
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| 08:41 | hair follicles of the South little cilia one direction. When it moves back |
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| 08:47 | Thio, it's in simulated position. can see again, the cilia has |
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| 08:52 | , and when the basilar membrane moves , the cilia, instead of moving |
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| 08:58 | left to right, is bend from to left. This angle. So |
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| 09:05 | each movement, with each vibration off oval window and the movement off the |
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| 09:13 | , what happens is you have a of the bezel on membrane, which |
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| 09:18 | displaces the hair cells going up one , going down another direction, going |
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| 09:25 | one direction, going down another And this is essentially what happens when |
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| 09:32 | are encoding the receptor potential. If bend the displays, you bend and |
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| 09:38 | sicilia some 10 nanometers to the You change the member and potential, |
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| 09:45 | is the receptor potential. These air receptor cells that will get Mawr D |
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| 09:50 | . Bending this direction 10 nanometers. Even mawr means it's even bigger shift |
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| 09:58 | shift, so you have even greater polarization. Now when you bend back |
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| 10:05 | place the basilar membrane back to its , you don't have any change in |
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| 10:11 | potential And if you displace the silly the opposite direction, you actually get |
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| 10:17 | negative. I'm proposal arising changing So the movement of the silly and |
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| 10:25 | to left represents right Deep polarization left polarization right. Deep polarization left hyper |
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| 10:32 | . So you have the sign you Sinus oId waves coming in those |
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| 10:38 | Our remaining sign you saw it in fluid and the sound pressure that is |
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| 10:43 | oId eventually gets converted into a hair receptor potential that a Sinus oId so |
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| 10:51 | deep polarized membrane up the hyper polarized down deep, polarized, hyper |
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| 10:56 | So this is the encoding of the that happens, and what happens is |
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| 11:02 | conversion of the mechanical movement off the mechanical movement off the bones. Mechanical |
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| 11:08 | off the, uh, membrane and movement of the fluid is now converted |
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| 11:15 | changes in the electrical potential and the potential of these hair cells. So |
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| 11:24 | is another illustration that shows you three of hair cells, and you can |
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| 11:31 | that it's silly of protruding here. , and you can see that these |
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| 11:36 | three rows of outer hair cells and can see that the cilia is embedded |
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| 11:40 | on the territorial membrane. This is Micrografx. Picture the same as your |
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| 11:46 | by the cartoon. Here you have pictorial membrane and you have the stereo |
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| 11:51 | projections from the hair cells that are . So in this number rains every |
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| 11:56 | the number and moves, the cilia to move with it. Uh, |
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| 12:02 | if you have damage to hair the damaged typically happens Cicilia. And |
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| 12:07 | the cilia becomes detached from the dictatorial or it's not properly attached anymore, |
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| 12:14 | there's some damage to hairstyles and you have hearing problems, no notice. |
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| 12:22 | thing is that you have these three of outer hair cells. Then you |
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| 12:28 | the Axiron. Is that the the that are coming to these outer hair |
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| 12:36 | ? And you can see in this even hear that there's a lot more |
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| 12:41 | that's coming from the from the inner salts rather than the outer hair |
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| 12:47 | So we will discuss why that is , and the fact is that most |
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| 12:52 | the information that we get into the pathways comes from the inner hair |
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| 12:57 | But these three rows of outer hair allow us to amplify that information that |
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| 13:04 | being encoded by the inner hair cell allowed Thio amplify the movement of the |
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| 13:09 | . Auriol membrane is well, So does this work These? The |
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| 13:15 | A gated transient receptor potential? A channels. That's what trip stands for |
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| 13:22 | transient receptor potential channels and these channels promotable to potassium. These channels are |
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| 13:32 | along all of the cilia and these channels. Air also connected through tip |
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| 13:39 | . So if you bend the serious into this direction into the right |
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| 13:44 | you open one channel, and as bend the cilia, it pulls on |
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| 13:51 | tippling, and as it pulls on stippling, it opens up more potassium |
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| 13:55 | , um, or potassium comes in it opens up Maura adjacent stereo |
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| 14:00 | potassium channels or more. Potassium is in, and as potash in comes |
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| 14:05 | from the ambulance, remember that we that this is unlike the regulation of |
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| 14:12 | , and this is unlike the typical fluid. So we have high Miller |
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| 14:18 | , concentrations of potassium and the Elim on potassium enters into the hair |
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| 14:24 | and deep polarizes. Um this deep in the hair cells opens voltage, |
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| 14:30 | calcium channels and influx of calcium. , of course, is necessary |
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| 14:36 | in addition to deep polarization in calcium release the neurotransmitters from these hair cells |
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| 14:45 | the spiral ganglion Nure i'ts. so again, this is the connection |
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| 14:55 | is coming into okay, Don't There's no axon that's coming out off |
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| 15:00 | hair cells. It's the connections that coming from spiral spiral ganglion cells and |
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| 15:08 | accents that they have connected to these cells. Uh, so in a |
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| 15:14 | , this is like a peripheral Axiron goes and gets connected to the outer |
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| 15:19 | inner hair sauce. These air the so the spiral ganglion cells and these |
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| 15:24 | the central accents that well done project the auditory processing pathways. Now, |
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| 15:32 | thing to notice is if you bend stereo, Sylvia, one direction you |
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| 15:37 | influx of potassium. You have deep calcium, and you have more neurotransmitter |
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| 15:42 | . But if you move this Sarah in the opposite direction, you cut |
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| 15:47 | the influx of potassium and deep I'm cut off. Yeah, |
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| 15:51 | and therefore you hyper polarized the cells and you cut off the neurotransmitter release |
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| 15:58 | swell. So outreach aerosols outer hair . Also special because they have these |
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| 16:09 | proteins, these motor proteins that are in the actual plasma membrane off the |
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| 16:18 | hair cells. And by that this this this motor proteins. They're |
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| 16:24 | of like springs. They can They can get, get smaller and |
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| 16:32 | , and they can expand these air motor proteins. And if you have |
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| 16:38 | movement in the other direction and depending the silly and the other direction, |
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| 16:44 | have the compression of these motor And so, by expanding and compressing |
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| 16:50 | motor proteins without her hair cells, is the amplifying the movement of the |
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| 16:57 | the membrane with respect to the tech alone membrane. This is when it's |
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| 17:03 | normal. Respond with cochlear amplifier, then you can actually dampen the activity |
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| 17:09 | you can see that you can dampen . And outer hair cells would be |
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| 17:13 | for this amplification through the very specialized motor protein structures here, essentially making |
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| 17:21 | that the roof really moves stronger so the inner hair cells from which most |
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| 17:26 | information is communicated to the central pathways really passing that information on properly and |
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| 17:34 | it thio the highest fidelity. So our spiral ganglion cell. And now |
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| 17:41 | we're gonna do is we're gonna apply knowledge of anatomy. And the way |
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| 17:45 | you read this diagram here on the is you look at the level of |
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| 17:51 | each cut is made here on the brain structure. So this first cut |
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| 17:57 | here made a to the level of ventral cochlear nucleus. Okay, in |
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| 18:05 | olive right here, number one number is made at mid brain, where |
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| 18:11 | have the inferior curriculums that's involved in information processing. Number three cut here |
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| 18:20 | the cross section or coronal section through brain that exposes the auditory topless coming |
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| 18:30 | the follow most of them to the cortex. So let's walk through this |
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| 18:36 | pathway, and it's a little Remember, it was a retina thalamus |
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| 18:42 | . This is different. This is KLIA, auditory nerve fibers, the |
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| 18:48 | , Coakley and our fibers from spiral cells, not from retina Jinich. |
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| 18:55 | , DJ Nicholas houses a spiral ganglion . It's from spiral ganglion cells projecting |
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| 19:04 | the ventral cochlear nucleus located here and crossing over into the superior olive. |
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| 19:15 | crossing it over hear some sounds remains one side another, another pathway here |
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| 19:23 | over at the level of the Stop from their projections from the superior |
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| 19:32 | through the pathway that's called lateral meniscus in to the inferior curricula. |
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| 19:40 | Inferior curricula asses a part of corporate Gemini The four body uh um nuclei |
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| 19:51 | empirical IQ. Youlus is concerned with information processing. You may recall that |
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| 19:58 | we talked about the visual information we talked about the superior curricula so |
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| 20:04 | curricula superior. Inferior calculus is part the corporate Quadra Gemini. But for |
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| 20:08 | auditor information processing information goes through and curricula us before guests to the medial |
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| 20:16 | Hewlett nucleus, M G in or Hewlett nucleus is medial thio. The |
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| 20:24 | judicial in nucleus was processes the visual and then from the media. Logical |
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| 20:30 | nucleus, which processes the auditor The primary the pathways goes into the |
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| 20:38 | auditory cortex, located in the temporal , so this is quite different than |
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| 20:46 | more complex here and goes through brain vision didn't go through brain stem vision |
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| 20:54 | . I thala mus cortex here we're about here. Brainstem, midbrain, |
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| 21:02 | and then cortex. Important things to is inferior. Caligula stalks to superior |
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| 21:10 | . Us. Do you remember the of superior Caligula? See, category |
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| 21:16 | , fast eye movements. So if heard something you'd wanna almost reflexively there |
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| 21:22 | a loud sound that is processed by Oculus at the level of the brain |
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| 21:28 | . This is your reflex. This the movement of the ice that is |
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| 21:35 | . Okay, It happens. At level of the brain cell is visual |
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| 21:38 | that goes into brainstem to superior Auditorium put that goes in fear |
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| 21:42 | They both talk to each other. is not you processing. Listening to |
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| 21:48 | Art Symphony's and looking at the paintings , uh, famous artists. It's |
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| 22:03 | , voluntary listening and moving your psychotic eye movements and some basic rudimentary |
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| 22:09 | information processing brain sim neuron sends feedback the outer hair salts. Whoa, |
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| 22:20 | stem neuron sends feedback to the outer cells. Wow. So you have |
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| 22:31 | cortex, remember? We have the cortical from cortex to Solomon's. You |
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| 22:36 | auditory cortex that talks Thio, MGM talks to empirical Oculus and the brain |
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| 22:47 | . Okay, brain stem communicates back the outer hair cells. We didn't |
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| 22:55 | that individual system. There was nothing was communicating information doctored the photo |
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| 23:04 | Once the information exited out of the , there was no input going back |
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| 23:09 | the retina to contact the photo And in this case, you have |
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| 23:15 | hair cells that you have a feedback . So you get sent back from |
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| 23:20 | to outer hair cells. So at level of the brain stem, you |
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| 23:25 | some sort of a rudimentary regulation off sensory input, potentially gating, potentially |
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| 23:33 | the game off the sound, amplifying or dampening the sound outside at the |
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| 23:42 | again at the cochlear nucleus. these initial projections the sounds are either |
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| 23:51 | coming just from one eye. But all the other nuclei Sapir, |
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| 23:56 | olive and then fear curricula us. sound is by aural. So the |
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| 24:01 | and superior olives and inferior calculus uh, the information there's crossed over |
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| 24:07 | get information is coming from both So this is really interesting. You |
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| 24:16 | , we talked about the somatic sensory mean, we talked about the visual |
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| 24:20 | , a sort of a canonical central information processing system for vision and anatomy |
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| 24:30 | the projections on the connectivity of that . And you can see that there |
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| 24:36 | definitely big similarities. But the projections are also quite different. Let's discuss |
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| 24:44 | tonal topic maps a little bit. we already talked about that at the |
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| 24:48 | . You have high frequencies off the and that the banks to process low |
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| 24:56 | . And guess what? If you at the spiral ganglion cells atone a |
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| 25:00 | map what cells are connected to what ? Hair cells and inner hair cells |
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| 25:07 | the spiral ganglion, if they're connected 16 kilohertz, will carry that 16 |
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| 25:12 | information all the way through the auditory into the cochlear nucleus and all the |
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| 25:19 | here that has shown passing through all way into the primary auditory cortex. |
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| 25:26 | in the visual world, we had ocular dominance left, right, left |
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| 25:31 | . But here we actually an orientation for the signals in the primary visual |
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| 25:38 | . Now we have here frequency selectivity basically, if you were record from |
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| 25:45 | in the primary auditory cortex. In area, there will be most responsive |
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| 25:49 | low frequency sounds and in this area will be most responsive to high frequency |
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| 25:54 | . So this point by point in case, it's not point by point |
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| 25:59 | field. It's not actually the auditory . You see it in outside world |
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| 26:04 | localization of sound. It's the auditory . It is based on the frequency |
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| 26:10 | with certain hair cells receptor cells on along the pathway to the primary auditor |
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| 26:18 | processing that specificity for certain frequencies is in the way you can think of |
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| 26:25 | . This is the receptive field properties the auditory neurons because they're not |
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| 26:30 | they're receptive fields and what their their are in processing the frequencies of |
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| 26:40 | We are pretty good at sound and there are some things that we |
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| 26:46 | every day that help us localize, pretty fast. If you have good |
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| 26:51 | , sound comes in waves, so know that if it comes from the |
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| 26:57 | direction over the other, let's say sound is coming from the right, |
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| 27:00 | waves air coming. It's gonna hit right here first. If the sound |
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| 27:05 | coming from the front. It hits front first, the side of your |
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| 27:11 | 0.3 milliseconds later and your ear 0.6 later. But you're if you're facing |
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| 27:18 | directly in front of you, then ears will be hit at the same |
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| 27:24 | . And behind you you will form is called the sound shadow. So |
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| 27:28 | will shadow some of that sound as sound waves of traveling through the |
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| 27:33 | If the sound is coming from the , you will have sound chat on |
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| 27:37 | left and you will know it's coming The right is gonna be louder and |
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| 27:41 | going to come in there fast and gonna be quieter and it's going to |
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| 27:44 | in here second in this direction. of course it could come in different |
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| 27:49 | . And so this this this first all, the sound itself in the |
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| 27:54 | and anatomy in the in the penny structured in such a way that it |
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| 27:59 | allows us thio drive and angular late sound waves and direct them into the |
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| 28:06 | auditory in the eighties. And because have different angles of sound and |
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| 28:12 | shadows of different angles. Now you localize the sound with your eyes closed |
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| 28:17 | well. Which direction to sound is from? No, let's look at |
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| 28:23 | an example of how you can say the signal is coming from the right |
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| 28:29 | from the left on how this is in the system. So let's say |
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| 28:34 | sound from left side. It's coming the left side and increased activity in |
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| 28:39 | left cochlear nucleus activities then sent to superior Olive. Yeah, sounds from |
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| 28:49 | in the left and the superior Now what you have is accents from |
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| 28:53 | cochlear nucleus. They have action and as these accents arrived in the |
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| 28:59 | olive and you have ah tona topic . But you also have the connectivity |
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| 29:05 | . This action potential will head on juan synapse with some delay on your |
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| 29:10 | , too, and with some delay your on three as the sound here |
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| 29:16 | can see on the left is the wave crosses over your head and now |
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| 29:21 | on the other side. That's when have activation of accents from the right |
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| 29:27 | nucleus, which for Jackson to superior and What happens is the two acts |
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| 29:34 | acts on actual potentials from these different they will meet and the connection number |
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| 29:43 | on your own. Number three. you will know in this map where |
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| 29:48 | sound is coming from because 12 is be already active. And all of |
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| 29:53 | sudden simultaneously, you're gonna have activation the starting your own. So both |
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| 29:58 | reach Oliver Neuron three at the same . Although the impulse started on the |
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| 30:03 | side much sooner, it activated some on the way in Summation of synaptic |
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| 30:10 | here will generate an action potential from you can. It's either the deep |
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| 30:19 | . So the action potential. So this the fact that you activated here |
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| 30:25 | activated an action potential in neuron three significant enough deep polarization. Now you |
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| 30:30 | that the sound was coming from but that just encoding the map. |
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| 30:35 | this is how you can localize. sound is basically by different sound |
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| 30:40 | Here's a different times, and through map of connectivity, informing the brain |
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| 30:48 | where the sound is coming from by sequentially synopsis of neurons that could converge |
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| 30:55 | different parts if it was coming from right first of with converge on one |
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| 30:59 | of three. So let's talk about impairments, actually, and we have |
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| 31:12 | common hearing impairments that are divided into hearing impairments and sensory neural area |
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| 31:20 | Conduction hearing impairments has anything to do conducting the sound to the cochlear, |
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| 31:28 | , conduction impairment, calcification of rupture of air drum ear infections, |
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| 31:39 | , air wax abnormal air wax production will prevent the sound to be |
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| 31:45 | So anything that kind of dampens the . Sensory neuro refers thio damage to |
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| 31:53 | cells and the damage to hear sauce be permanent, and the most common |
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| 32:00 | of damaged hair cells is referred to tinnitus. And people can say, |
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| 32:05 | , my ears were ringing. And know what? When your ears are |
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| 32:10 | , you can hear it, and can hear my ears ringing because I |
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| 32:15 | have tinnitus and I'll tell you how happened to me. So you go |
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| 32:20 | your concert when you listen to loud and it's kind of loud. And |
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| 32:25 | if you go and expose yourself to loud sound, you come home and |
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| 32:32 | hearing his damp and you can hear while you say my ears were plugged |
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| 32:38 | like flying. And so the following you wake up. Oh, my |
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| 32:41 | are still a little bit plug. then maybe a day later, you're |
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| 32:44 | of a year and comes back to . And even during that period, |
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| 32:50 | your years applaud, you also may hearing a little bit of kind of |
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| 32:54 | ringing or whistling. And that goes . So for me, tinnitus started |
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| 33:02 | I wanted to concert on the group my friends decided to come closer to |
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| 33:07 | speakers to mean, and Chaka Khan on stage and the music equipment was |
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| 33:17 | off and even commented. I set high pitches so turned out, it's |
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| 33:22 | unbalanced sound. We stood there trying catch up with our friends for maybe |
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| 33:29 | minutes. It was so loud and Lee loud by the speaker said, |
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| 33:33 | actually left and I had plugged ears night, and then I woke up |
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| 33:39 | the morning and my ears were plugged I had drinking. It's okay in |
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| 33:45 | evening, my ears were plugged and still had ringing following morning, my |
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| 33:50 | were plugged and I still had So I went thio doctor, and |
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| 33:56 | took a hearing test. I Yeah, you lost some hearing in |
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| 34:01 | of your years. I said, , I lost it, but it's |
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| 34:06 | come back and maybe your test is and well, the doctor said, |
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| 34:12 | , but it's it's rare and I how you feel. But you're likely |
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| 34:17 | to gain that hearing back and may have persistent tinnitus senators. Okay, |
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| 34:26 | I said, I don't believe I'm going to come back in 23 |
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| 34:29 | and you're gonna test me and you're to see that my hearing is |
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| 34:33 | And of course, I went back weeks and they took a test |
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| 34:38 | Sorry, buddy, you're hearing is bad. How is that ringing? |
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| 34:42 | said it's bad. So they gave some steroid medications and wasn't helping that |
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| 34:49 | with it at all. And then exacerbates the tinnitus years. Really ringing |
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| 34:56 | makes it ring. So what is ringing? This is you killed some |
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| 35:01 | cells. You destroyed some cilia and your pictorial number and is loose and |
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| 35:06 | essentially vibrating almost all of the times you lost the proper structure underneath this |
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| 35:12 | ringing is it's a loss of hearing partial loss of hearing we It's a |
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| 35:19 | frequency hearing that gets affected, close to the base and the sounds |
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| 35:25 | actually process the auditory. The vocal voices are at the at the corner |
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| 35:35 | the bend of the cochlear. So get preserved actually the longest if you |
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| 35:39 | ah, damage Thio co created to to the hair cells into the |
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| 35:44 | Just anatomy itself protects us from losing range that allows us to understand the |
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| 35:53 | language. Um, now, if have permanent hearing loss and then it's |
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| 36:01 | significant, then you may have a option off cochlear implants and cochlear |
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| 36:08 | and it's something that is shown So you have ah, skin. |
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| 36:16 | then on the surface of the skin you have receiving antennas and these receiving |
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| 36:23 | are connected to basically you have microphones a receiver circuitry and the sound processing |
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| 36:31 | then each one of these electrodes you a long sort of you in sort |
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| 36:40 | a long electrode into this coiled Okay, insert that and along |
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| 36:50 | uh, insert, you have many electrodes. And so you make sure |
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| 36:56 | the high frequency sound coming from and by the receiver here is activating the |
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| 37:05 | frequency cells. In this case, hair cells air lost. So what |
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| 37:13 | doing is you're stimulating the spiral ganglion , so if you damage the hair |
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| 37:19 | , their hair cells do not You do not gain your hearing back |
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| 37:24 | a while. Miraculously, just the . Usually with age, the hair |
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| 37:29 | age and you have for for a . So if you're missing the hair |
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| 37:36 | , you have damage to the Of course you are. You can |
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| 37:41 | . Then you have these electrodes and have hundreds of these electrodes micro electrodes |
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| 37:49 | are part of this insert here that process the sound and will segregate the |
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| 37:55 | based on the frequencies and will stimulate frequency spiral ganglion south close to the |
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| 38:01 | on low frequency. The response to ganglion south, close to the helical |
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| 38:08 | and the apex of the cocorium. , so, again, this is |
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| 38:14 | sensory neural damage is damage to the . Damage to the hair sauce. |
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| 38:21 | , uh, this is a way combating that damage through the cochlea |
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| 38:31 | In this case, we're going to the barn owl, and we will |
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| 38:36 | what a sophisticated sonar and what a sound localization system the barn halls |
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| 38:45 | So enjoy this, uh, short . About 2.5 minutes. 34 |
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| 38:53 | Almost. It turns into the empty . The noise of wind and snowfall |
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| 39:02 | filtered out, its rustling that the is interested in a false alarm, |
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| 39:14 | it doesn't have to wait. Long deep under the snow, a lemming |
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| 39:21 | a high frequency Russell on around The penalty for rustling is death |
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| 39:29 | The signals are too weak for our , but this hour has the ultimate |
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| 39:35 | . It's face acts like a satellite . Dish is formed by a ring |
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| 39:42 | stiff feathers. They collect and channel inwards. Eyes look central, but |
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| 39:52 | dish actually focuses on the ears. on the side of the tiny skull |
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| 39:57 | to the eyes with the dish is by a lane of bristles giving stereo |
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| 40:09 | . It's like having a giant cupped behind each year. Yeah, photo |
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| 40:25 | able must tune it receiver the dishes . The eyes automatically follow too |
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| 40:35 | then back again. The lemming is being totally reckless. Sound dish and |
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| 40:46 | are now focused. From this point , it won't look away until the |
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| 40:53 | is in its talents. Resort Els approach is absolutely silent. |
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| 41:11 | velvety feathers have serrated edges that simply the here as a result, nor |
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| 41:17 | flaps interfere with the lemmings. Transmission remains focused at all times, even |
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| 41:30 | it has to fly around obstacles beneath carpet of snow. A stationary target |
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| 41:47 | easy Thio, but it's not just simple dive. Bomb attack head stays |
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| 41:59 | on until the lie last moment. the talons air raised into the line |
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| 42:04 | the sound booth. Claws on each are extended to above and two |
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| 42:15 | perfect for catching cylindrical dream lemmings. is up. Even if the lemming |
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| 42:23 | moving, the owl can compensate. owl hovers. It checks signal |
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| 42:31 | Body twists on the talents of When you're dealing with senses, this |
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| 42:43 | specialized physical defenses like snow can be . E finally figured how do exit |
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| 43:01 | . Okay, this is the beginning the discussion on somatic sensory system. |
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| 43:09 | funny images you see here on the is called the homunculus. And the |
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| 43:14 | why it has such abnormally exaggerated arms lips, especially in some other parts |
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| 43:19 | the body, is this is a like representation of how much of your |
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| 43:25 | sensory cortex is dedicated to which organs the body a lot of fine movement |
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| 43:30 | motor control. A lot of sense and touching comes from the hands of |
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| 43:36 | and lips and movements and years and sexual organs and arousal. But not |
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| 43:43 | much space is dedicated to torso, actually dedicates a lot of space anatomical |
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| 43:48 | the human body so that a sensory processes, uh, somatic sensations, |
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| 43:56 | stimuli of pressure appropriate exceptional position of and muscles with respect. Thio the |
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| 44:06 | world where the muscle, how the and joints are activated. Distension of |
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| 44:13 | , temperature of limbs and brain so have temperature receptors. You have chemo |
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| 44:19 | , and you have pain. Receptors are part of this amount of sensory |
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| 44:24 | receptors in this case are unique. widely distributed throughout the body, so |
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| 44:29 | we talked about receptors individual system. was indirect mint when we talked about |
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| 44:36 | in the auditory system that was in cocorium. What we're talking about. |
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| 44:40 | for somatic sensations air all over our and face and head, mostly processing |
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| 44:51 | senses to touch, temperature, pain appropriate exception. It is important to |
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| 45:00 | and remind ourselves some basic anatomy of skin here, which consists of the |
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| 45:07 | or the service layer of the skin the Durmus, or the deeper layer |
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| 45:10 | the skin that is now connected to fatty tissue. And we have, |
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| 45:17 | , two types of skin. We glamorous skin and we have hair |
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| 45:22 | We'll see. Harris Skin is illustrated , and you have the hair |
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| 45:29 | the hair roots here and what you're . These is different. Nerve endings |
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| 45:37 | different receptors that are gathering the information the skin. You have free nerve |
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| 45:45 | . You have Pechiney, um, puzzles. You have Ruffini sendings. |
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| 45:51 | have Meisner score apostles and they're distributed the dermis, a different extent of |
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| 45:59 | dermis and the relationship to the skin to the hair follicles and heroines. |
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| 46:07 | is the largest organ of our You cannot survive with our skin. |
|
| 46:16 | cannot live without a skin. Significant of skin due to Barnes, |
|
| 46:24 | can be deadly. Skin is, , not only very large or the |
|
| 46:33 | organized the body. It is the expensive organ in our body. It |
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| 46:44 | the organ on which we spend a of money. We use shampoos and |
|
| 46:55 | , hair dyes, moisturizers and so and so forth. Hyaluronic acid, |
|
| 47:07 | , CVD, whatever. Everything. e, vitamin C and tyrannical |
|
| 47:17 | Anti aging, anti inflammatory healing Whoa. Talking about hand sanitizers. |
|
| 47:31 | , so the microbes live on the to massive massive industry tattoos, a |
|
| 47:41 | removal. It's all there. so just think about skin that, |
|
| 47:49 | know, we look at it as superficial thing for beauty a lot of |
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| 47:54 | or looks, but indeed, it a very important organ that's connected to |
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| 47:59 | lot of nerve endings. And, , modern day society pays a lot |
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| 48:05 | attention. Thio what is being fed the skin and through the skin. |
|
| 48:14 | , when we talk about receptive fields , it's really easy. It was |
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| 48:20 | to understand receptive field properties off the cells and retina GM and primary visual |
|
| 48:29 | . Here, the receptive field is actual receptive field on the surface of |
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| 48:34 | skin. So you have the Meisner . Apostles remember, we have these |
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| 48:39 | score puzzles here and there. They have small endings here, and |
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| 48:45 | they have small, receptive fields. you'll have miser score puzzles, especially |
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| 48:50 | located at the thin that index It's a finger that you use the |
|
| 48:55 | . If you look Pechiney Encore possible fields are much larger because they're actually |
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| 49:00 | larger core puzzle itself in the in ending that is, processing that |
|
| 49:08 | And so you have this What is , uh, two points discrimination test |
|
| 49:17 | can take to objects you can take , uh, pants. You can |
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| 49:24 | two fingers and you can touch your , and you can move those fingers |
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| 49:30 | closer the closer, the closer, closer. And you can still say |
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| 49:33 | it's two fingers. You can do same tests on the course of loves |
|
| 49:38 | eyes and somebody will touch you and say You're touching me with two |
|
| 49:42 | two fingers, two fingers. If spread. But if it comes |
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| 49:46 | I can't tell if it's two fingers one. Okay, special if the |
|
| 49:50 | is small, so you have very , receptive fields at the level of |
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| 49:55 | torso. 42 millimeters wide at the that is not very sensitive, even |
|
| 50:02 | . And then you have very small find receptive fields that are located in |
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| 50:07 | in the index finger and, of , located in the face and the |
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| 50:11 | the mouth of lip region. So not only receptive field size that's important |
|
| 50:19 | also the adaptation and how they react the somatic stimuli you have. |
|
| 50:26 | Uh uh, those Air miser score , opportunity, um, core |
|
| 50:32 | And you have slow adapting on these Merkel's discs and roof finis endings. |
|
| 50:39 | means that with rapid adaptation, Meisner apostle as soon as you stimulate the |
|
| 50:45 | . It produces a lot of action , and it adapts to that very |
|
| 50:49 | . Samos petunia and carrot possible. with Merkel's disk or Ravinia endings, |
|
| 50:55 | somatic stimulation activist Merkel's This is actually of slower, so you will still |
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| 51:03 | producing action potential. Aspiring away during stimulus, not only during the initial |
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| 51:09 | , so to speak. But also the actual continuous touch, you will |
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| 51:15 | a continuous number of action potentials. think about Adaptation is something that you |
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| 51:24 | every day, somatic adaptation. A example is if you buy a new |
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| 51:32 | on new government and you put it , and at first, when you |
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| 51:36 | it on, maybe it steals a bit uncomfortable. You adjusted and you |
|
| 51:40 | it for a couple of seconds, then it goes away. So you |
|
| 51:43 | quite a bit of the adaptation of , uh, somatic sensory nerve |
|
| 51:50 | Otherwise, and if you have abnormal sensations, you may be irritated by |
|
| 51:57 | a shirt the whole day is may you just just not adapt and just |
|
| 52:03 | you. And that is a certain that happened with hypersensitivity and with the |
|
| 52:10 | of adaptation. So why use fingertips Braille reading? Because you will have |
|
| 52:17 | high density of the receptors and the with the smallest receptive fields To discern |
|
| 52:23 | highest degree off spatial resolution. You small, receptive fields. You have |
|
| 52:32 | rain tissue that's devoted according to the , Uh, and there is special |
|
| 52:39 | mechanisms that are also associated with with resolution discrimination that are that are potentially |
|
| 52:47 | of the actual touch but is connected higher cognitive centers in a way, |
|
| 52:55 | we have these major primary affairs. already learned these primary appearance that are |
|
| 53:03 | in this dorsal root ganglion cells entering the dorsal spinal cord. We have |
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| 53:10 | appropriate sectors on you have group one that are the largest in diameter and |
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| 53:17 | the fastest and conductivity because they're so and they're my eliminated group to fibers |
|
| 53:25 | mechanical receptors of the skin. They're to 12 micro meters in diameter, |
|
| 53:33 | they are a little bit slower than . Very large appropriates after fibers for |
|
| 53:40 | skeletal muscles, the pain and temperature by the smallest type three fibers that |
|
| 53:51 | the smallest in diameter, the slowest processing that information. And then you |
|
| 53:57 | a mile in ated uh, He's Ah, Alfa Alfa A data |
|
| 54:07 | delta, and then you have C to refer to them or group four |
|
| 54:12 | that are on the myelin native, they process temperature, pain and |
|
| 54:19 | They're the smallest in diameter there the in there because they're in myelin |
|
| 54:24 | They're also don't have very much off tile power, so to speak. |
|
| 54:31 | is the best example that I um, into understanding the speed, |
|
| 54:37 | of the transmission and the speed of reaction of these different fibers? And |
|
| 54:43 | go to one of my favorite stories Dr House E I. I watch |
|
| 54:53 | episodes off this syriza, and I say that I'm like a huge fan |
|
| 54:58 | that serious. But I was listening an interview with Dr House, and |
|
| 55:04 | said that when he was a he had this strange, um, |
|
| 55:12 | or affliction off. How long will be able to hold his hand in |
|
| 55:19 | bucket off eyes? Uh, you , for issues own that that was |
|
| 55:27 | thrills By trying to guess, push limits of how he's going to react |
|
| 55:34 | really eyes called water temperature to with hand and the reason why I bring |
|
| 55:42 | sub. So maybe you'll remember Dr . Maybe you'll remember bucket of |
|
| 55:48 | Maybe you'll remember your own experience of to grab something from the cooler, |
|
| 55:53 | finding. And then, after some actually withdrawing your hand because he's getting |
|
| 56:02 | . So let's imagine a situation where have water, very cold water with |
|
| 56:10 | , and we're gonna take our We're gonna close our eyes. We're |
|
| 56:14 | try to bring this hand into the of ice. And as we bring |
|
| 56:18 | hand into the bucket of eyes, appropriate exception is going to inform us |
|
| 56:23 | the bending of the muscles off the . Okay, where it's located, |
|
| 56:29 | mechanical receptors. When you touch the off the water, it's a different |
|
| 56:35 | . There's ice mechanic receptors are gonna you. You're touching something different. |
|
| 56:42 | some time, that different is going seem cold to you. And after |
|
| 56:48 | longer time, if you manage to your hand on that ice water, |
|
| 56:52 | will start feeling pain not just the temperature but paying from that ice water |
|
| 56:58 | which you're likely to withdraw your hand tried to warm it up. So |
|
| 57:05 | only thing that we haven't mentioned here each. But this whole progression should |
|
| 57:12 | you first is appropriate exception. Then am I touching? Mechanical, Then |
|
| 57:16 | it Ah, hot object or called it's called, can I keep my |
|
| 57:21 | until it gets so painful? The fibers get activated. And then if |
|
| 57:25 | irritate your skin, long and I be subjected to long enough of the |
|
| 57:29 | change or another stimulate, maybe even nauseous stimuli. You will feel hitch |
|
| 57:35 | inches of persistent activation of these on myelin native fibers. Uh, that |
|
| 57:41 | activated. Uh, Thio essentially send signal onto the higher processing center. |
|
| 57:49 | please remember the example off the four . It's easy, biggest, fastest |
|
| 57:56 | they have this located. Appropriate I cannot receptors what I touched |
|
| 58:03 | What? What? What? I'm pain. I'm feeling pain and then |
|
| 58:08 | is a modern native fibers. So , uh, we're about thio. |
|
| 58:18 | mawr most amount of sensory system. I see that I have actually fallen |
|
| 58:24 | some of the material on the somatic system. And what I would like |
|
| 58:31 | do is just walk you through this cord and Dermot Tone anatomy, and |
|
| 58:37 | going to take a break and we'll up the amount of sensory system the |
|
| 58:43 | writer. So if you recall we divisions off the vertebra and the spinal |
|
| 58:49 | into the cervical, thoracic, lumbar sacral spinal cord and each one off |
|
| 58:55 | spinal nerves. That air coming in between each one of the segments has |
|
| 59:00 | own zone on the skin, it's derma Tone, So German tone is |
|
| 59:08 | that's innovated by these sensory dorsal root fibers, or one side by single |
|
| 59:16 | segment. So everything on the back the head on the skin when you |
|
| 59:21 | this process by C. One C on the next C three. C |
|
| 59:26 | c 567 If you touch this this process just by C one on |
|
| 59:33 | right, this side See one on left, these Air Derma Tom's and |
|
| 59:38 | precise connectivity. And if you took the whole human anatomy here, then |
|
| 59:44 | drew the Dermot Tones. Are correspondent use spinal nerve? This is exactly |
|
| 59:50 | drawing that you would have, where have the most lower sacral spinal nerves |
|
| 59:56 | out of the spinal cord. Supplying most lower extremities as well is |
|
| 60:01 | uh, sexual organs here and, , uh, muscles and the gluteal |
|
| 60:12 | and where you have, of the Urus IQ is gonna be all |
|
| 60:16 | the thorax and cervical is gonna be , the upper limbs and the back |
|
| 60:22 | the head. This is a Dermot . This is another examples of derma |
|
| 60:29 | , and Dermot tones are relevant, it's relevant. Thio what we see |
|
| 60:36 | in the form of the disorder called and if you heard of shingles. |
|
| 60:42 | maybe you have even seen vaccinations for for shingles being advertised in the pharmacies |
|
| 60:52 | his shingles. So shingles happens as a child, if you were |
|
| 61:01 | with herpes zoster virus, which commonly known as chicken pox virus. So |
|
| 61:09 | happens after a week or so? get covered with red. It's your |
|
| 61:16 | on your skin can occur in different . It can be distributed on the |
|
| 61:22 | and could be in your arms and usually recover. And what happens to |
|
| 61:28 | virus from the periphery from the Antero Greatly. It travels into the |
|
| 61:37 | cord, and it stays dormant in single in the spinal cord. It |
|
| 61:49 | dormant. Okay, it stays dormant the primary sensor neurons, but |
|
| 61:55 | What does that mean? That means after some 30 40 50 years. |
|
| 62:02 | virus may get reactivated for a lot people. They never hear from this |
|
| 62:07 | again. But in some cases the revives, and it basically starts wreaking |
|
| 62:15 | on somatic sensory system. The result this is shingles. You can see |
|
| 62:22 | a single derma tome on the lower back of this person into the |
|
| 62:27 | here. And these shingles here is labeling one single Dermot tome. So |
|
| 62:33 | these herpes zoster virus reappears and reactivates the dust on just one single spinal |
|
| 62:47 | on one side, it's essentially like mapping of this Dermot own along the |
|
| 62:54 | that belongs to that particular spinal court on the dorsal root ganglion. So |
|
| 63:00 | being dormant now, it's retrograde goes back into the skin and cause |
|
| 63:06 | these massive rashes, invitation and And so when people say that all |
|
| 63:13 | is it just in its shingles is a niche right? Imagine you have |
|
| 63:18 | massive. It's just going across your in different parts. You cannot touch |
|
| 63:23 | very sensitive to clothing. You cannot . It's painful. It's not just |
|
| 63:29 | itch. It actually can be burning sensation from shingles. Uh, so |
|
| 63:34 | good news is that there is vaccination shingles now, virus reactivates Onley in |
|
| 63:42 | dorsal root ganglion. And this is way of nodding these derma tones. |
|
| 63:48 | we'll take a break. And when come back, we'll walk you through |
|
| 63:53 | , um, central doc ways off some out of sensor information. |
|
| 64:00 | look at the homunculus and the Look at the Samata topping rodents. |
|
| 64:06 | if we have time, we'll watch Chandra video. But if we |
|
| 64:10 | we'll come back and watch it after break. Mhm. So I'm gonna |
|
| 64:18 | here |
|
