Why would the transduction process in hair cells fail if the stereocilia as well as the hair cell bodies were surrounded by perilymph?
Endolymph, which is similar to intracellular fluid, surrounds stereocilia and hair cell bodies. It has a high K+ concentration and a low Na+ concentration. The high K+ concentration is responsible for a K+ equilibrium potential of 0 mV. As a result, when K+ channels open, hair cells depolarize, moving toward the equilibrium potential of K+, which is 0 mV. In contrast, neurons, which have a K+ equilibrium potential of –80 mV, hyperpolarize when K+ channels open. Perilymph has an ionic concentration similar to CSF, which is low K+ and high Na+. If perilymph surrounds the stereocilia and hair cell bodies, hair cells will not depolarize when K+ channels open.