Auditory structure - part 2 | Processing the Environment | MCAT | Khan Academy

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[@Alaa1992ish]

Kinocilia are not found in the cochlea, they are only found in the vestibular system (semicircular canals, utricle, saccule).

[@caitygart]

In my class notes we have it as that they're a part of hearing and connected with the stereocilia...but in frogs. It looks like he may have gotten confused a bit with frog hearing.

[@nathanimalable]

Thanks! these help a lot. I study the topic first and then watch one of your videos and it always helps

[@WaelAKamel]

Very helpful and educating, thanks a lot for the effort and the easy explanation.

[@ggonsg]

Soooo helpful as I do my presentation tonight for class!!!

[@krishnakrishnareddy9718]

u are helping us SO is much your teaching is so good thanks so much

[@krishnakrishnareddy9718]

u are very helpful for us because u reaching is fully understand thanks so SO so so so so so SO much grate job

[@jiageng1997]

3:15 Only the longest hair is called kinocilium. Otherwise they are just called cilia.

[@roshan459]

Stereo cilia

[@abdulaziz.9471]

very helpful

[@Sam-ir6iu]

Great vid

[@allieneureither5637]

Stereocilia, not kinocilia! kinocilia are only found in the vestib system

[@sriram-ss8uu]

no biggest stereocilia is called kinocilia

[@caitygart]

@@sriram-ss8uu They're found in frogs, but not humans, as part of the hearing system. :) I think that is where the mistake lies.

[@monday2471]

4:56 hair cells don't fire action potentials

[@ABCD-ie5xo]

I concur. The hair cells fire a graded potential - releasing a transmitter which synapses and activates the spiral ganglion cell, transmitting its action potential to the auditory nerve (vestibulocochlear) (CN VIII)

[@shaheenmalick5999]

Depolarization of hair cell causes release of neurotransmitter, not an action potential right?

[@alexandriadixon4878]

You need an action potential to release a neurotransmitter

[@juliandevouassoux6860]

Nartharaen Greenleaf not necessarily, you need calcium to release a neurotransmitter... the movement of the stereocillium in some directions opens some mechanically gated k+ channels and the influx of k+ into the cell (because of the high concentration of K+ in the endolymph) depolarizates it. That depolarization opens the voltage gated Ca2+ channels, and the calcium enters into the cell and trigger the release of neurotransmitters at the basal end of the cell, where are the fibbers of the cochlear nerve. The opening of voltage gated k+ at the basal part of the cell results in repolarization (the k+ goes out because of the low concentration of k+ in the perilymph)

[@juliandevouassoux6860]

Nartharaen Greenleaf it's all electrotonic, or graded, potentials (at the hair cells)

[@Sam-ir6iu]

Why would k+ and calcium fire an action potential? And not sodium

[@aftonet]

K+ depolarizes the cell because of the high concentration of K+ in the endolymph compared to the intracellular levels in the hair cells and the perilymph. Calcium facilitates the fusion of vesicles containing the neurotransmittors(glutamate in this case) and therefore chemical signal transmission to the auditory nerve. See Purve's Neuroscience for more information.

[@shivamsoni9763]

Why cochlea is sensitive to low frequency?? Please help me if anybody know it.

[@ABCD-ie5xo]

The range of human hearing is 20 Hz - 20,000 Hz. We can hear frequencies in that range, with no hearing loss.

[@caitygart]

The cochlea processes different frequencies in different parts. Near the base you process high frequencies, whereas as you travel up the apex, you hear lower and lower frequencies. Cheers!

[@Avoug]

I thought potassium was more concentrated inside the cell. Do you mean sodium?

[@valim.4101]

these hair cells are in a special kind of fluid called endolymph fluid which has an unusually high concentration of potassium, so it actually reverses the driving force and causes potassium to move INTO the cell instead of out like normal

[@aks4781]

Y

[@mikamikamikaxxx]

wait, then whats the differnce between kinocilium and stereocilium?

[@alexandriadixon4878]

I tried making sense of this from in my book, because I stumbled here too, I think the individual filaments is actually the stereocilia - which when there is a force (the fluid) the stereocilia gets bent toward the kinocilium - which my book says there's only one on a hair cell; and the pushing of the stereocilia toward it causes the cell to depolarize and then, well I haven't gotten to that part yet :)

[@aftonet]

Nartharaen Greenleaf Actually, the kinocilia are not present in adult mammals according to Purve's Neuroscience 4th edition.

[@alexandriadixon4878]

aftonet whether or not they're in adult mammals, they are in humans

[@aftonet]

Nartharaen Greenleaf Not according to the litterature; in humans, and other mammals, they regress and are not present after birth. They are present in fish and frogs, which were the model animals for a long time regarding the cochlear and vestibular systems.

[@alexandriadixon4878]

I'm not entirely sure what you're trying to say with "they regress" - regress doesn't mean they disappear, it means they go back to their previous state. Kinocilium is actively apart of the formation of hair bundles - a process which moves the kinocilium. Once the hair bundle is formed, in MANY mammals (MANY, not ALL), the kinocilium regresses - which means it goes back the place it was in before. In fish and frogs the kinocilium stays in the hair bundle - the reason for that is so they can detect the movement of the water around their bodies. Aquatic mammals will probably have this, which is why I said MANY instead of all (I'm not yelling, I just don't know how to do italics to emphasize). But mammals like us, who don't live in the water, don't have that need therefore the kinocilium moves back out of the hair bundle (or, regresses).