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.
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)
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)
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.
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
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!
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 :)
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.
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).
Kinocilia are not found in the cochlea, they are only found in the vestibular system (semicircular canals, utricle, saccule).
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.
3:15 Only the longest hair is called kinocilium. Otherwise they are just called cilia.
Stereo cilia
Thanks! these help a lot. I study the topic first and then watch one of your videos and it always helps
Very helpful and educating, thanks a lot for the effort and the easy explanation.
4:56 hair cells don't fire action potentials
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)
Stereocilia, not kinocilia! kinocilia are only found in the vestib system
no biggest stereocilia is called kinocilia
@@sriram-ss8uu They're found in frogs, but not humans, as part of the hearing system. :) I think that is where the mistake lies.
Soooo helpful as I do my presentation tonight for class!!!
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Depolarization of hair cell causes release of neurotransmitter, not an action potential right?
You need an action potential to release a neurotransmitter
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)
Nartharaen Greenleaf it's all electrotonic, or graded, potentials (at the hair cells)
Great vid
very helpful
Why would k+ and calcium fire an action potential? And not sodium
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.
I thought potassium was more concentrated inside the cell. Do you mean sodium?
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
Why cochlea is sensitive to low frequency??
Please help me if anybody know it.
The range of human hearing is 20 Hz - 20,000 Hz. We can hear frequencies in that range, with no hearing loss.
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!
wait, then whats the differnce between kinocilium and stereocilium?
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 :)
Nartharaen Greenleaf Actually, the kinocilia are not present in adult mammals according to Purve's Neuroscience 4th edition.
aftonet whether or not they're in adult mammals, they are in humans
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.
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).
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