@julieo4 I am so glad that cochlear implants have helped you and thank you for sharing your story. It is amazing when you can solve a problem with a medical breakthrough! We may be using different terminology to say the same thing. I found some documentation that explains the details about hearing and how it works, and some research into repairing hearing loss with stem cells.

I was speaking about the hair cells as being nerve endings on the cellular level and are the first cell that receives the mechanical sound waves and converts them to an electric impulse and passing that directly to the cochlear nerve. They call them sensory receptors, and because they actually generate an electric signal that crosses a synapse to the cochlear nerve, I think of them as nerve endings or at least specialized nerve cells. Classification can change in time so I don't know if they are thought of differently now. Of course those nerve cells connect to other nerve cells and so on until it forms the path way that carries hearing impulses to the brain. Nerve cells have a very long extension called an axon and that communicates with tree like branches of an adjacent nerve cell called dendrites. The nerve impulse has to transmit across the space between the nerve cells with the help of chemical neurotransmitters to send an electric signal to the brain and that happens very quickly and the hair cells also generate neurotransmitters. The hair cells can be damaged and stop functioning and can be shattered by loud noises. The video below explains how the ear actually amplifies the sound coming into it. A cochlear implant can bridge the problem area of damaged hair cells and communicate with nerve cells further up the line.

Here is a drawing I found that explains the cellular biology of the hair cells.
https://content.byui.edu/file/a236934c-3c60-4fe9-90aa-d343b3e3a640/1/module12/images/Cochlea2.png

A textbook description of hearing
https://open.oregonstate.education/aandp/chapter/15-3-hearing/

and a video showing physically how hearing happens
https://www.youtube.com/watch?v=GGqfRvCkt-w

There is also some exciting hope on the horizon for regeneration of hair cells with stem cells to repair hearing loss.
Here is an article from Harvard and excerpts from the article.

Excerpts:

"The cells that collect sound information from the environment and send it to the brain are called hair cells. We are born with about 11,000 hair cells in each ear, and they need to last. We experience the slow progression of hearing loss as these fragile cells die due to excessive noises, exposure to certain drugs, and aging. As hair cells die, nearby brain cells that once carried sound information to the audio processing part of the brain also expire."

"Regeneration of Hair Cells
HSCI scientists have discovered which stem cells can become hair cells as well as the molecules that bring about this change. Using this information, our researchers are developing techniques to grow hair cells in the laboratory and implant them into the ear.

Stem cells can also be used to screen for drugs that could stimulate the regeneration of hair cells. This method has already produced drugs capable of partially restoring hearing in deaf rats. The next steps are identifying the right mixture of drugs that will regenerate the largest number of hair cells and assessing ways that these drugs can be delivered to the ear. The success in rodent models will eventually lead to drug tests in human stem cells."

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