Why does potassium influx depolarize cochlear hair cells, unlike most other excitable human cells?
Answer and explanation
Correct answer: C. Endolymph surrounding stereocilia has an exceptionally high potassium concentration
The scala media contains endolymph, secreted by the stria vascularis, with an exceptionally high K+ concentration (~150 mM) and a positive endocochlear potential (+80 mV). The electrochemical gradient for K+ into hair cells is steep, so opening apical K+ channels causes rapid inward K+ flux and depolarization.
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