What is the function of the tip of the hair cell in utricle?
Correct Answer: Receptor membrane Depolarization
Description: ANSWER: (B) Receptor membrane depolarization REF: Guyton 12th Ed Pg 675 Hair cells are present in the utricle and saccule. Each hair cell has 50-70 small cilia called stereocilia and a large cilium called the kinocilium. The kinocilium is always located to one side and the stereocilia become progressively shorter toward the other side of the cell. Minute filamentous attachments almost invisible even to the electron microscope connect the tip of each stereocilium to the next longer stereocilium and finally to the kinocilium Because of these attachments, when the stereocilia and kinocilium bend in the direction of the kinocilium, the filamentous attachments tug in sequence on the stereocilia pulling them outward from the cell body. This opens hundreds of fluid channels in the neuronal cell membrane around the bases of the stereocilia and these channels are capable of conducting large amounts of positive ions. The positive ions pour into the cell from the surrounding endolymphatic fluid causing receptor membrane depolarization. Conversely bending of the stereocilia in the opposite direction can cause receptor hyperpolarization.
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