The different chambers of the ear each have a role in conversion of sound energy into action potential firing in auditory axons. Auditory sensory transduction depends on:

Question

BlackTom AI · Accepted Answer

Mechano-sensitive potassium channels that depolarize modified epithelial cells in the inner ear.

Sound-driven motion of the basilar membrane deflects the stereocilia bundle on the apical surface of cochlear hair cells. The relevant concepts are: hair-cell anatomy (stereocilia on the apical pole, basolateral membrane with Ca2+-gated release machinery), ionic composition of the fluids (endolymph bathing the apical surface is rich in K+ and has a positive potential ~+80 mV relative to hair-cell interior), and mechanotransduction (tension on tip links gates mechano-sensitive channels).

Step-by-step reasoning:
1. A pressure wave causes the basilar membrane to move, shearing the tectorial membrane and bending stereocilia on hair cells.
2. Tip links between adjacent stereocilia (located at the apical surface, not the basolateral surface) become tensioned; this mechanical tension directly opens mechano-sensitive channels at the tips of the stereocilia.
3. Because endolymph has high K+ and a positive potential, opening these channels allows K+ to flow INTO the hair cell (electrochemical gradient favors inward K+ current), producing depolarization of the hair-cell membrane.
4. Depolarization opens voltage-gated Ca2+ channels on the basolateral membrane, Ca2+ influx triggers vesicular release of glutamate onto auditory afferent fibers, and action potentials are generated in auditory axons.

Why the correct answer is correct: the primary transduction current in cochlear hair cells is carried by mechano-sensitive channels that permit K+ influx from endolymph, thereby depolarizing the modified epithelial (hair) cells and initiating neurotransmitter release to auditory neurons.

Why the other options are incorrect:
- "Tip-links that connect the cilia at the basolateral surface of inner hair cells": tip links do gate channels, but they connect stereocilia at the apical surface, not the basolateral surface — the option is anatomically wrong.
- "Cyclic nucleotide-activated cation channels that lie in the apical surface of outer hair cells": cyclic nucleotide-gated channels are key in olfactory and photoreceptor transduction, not the primary mechanism in cochlear hair cells; outer hair cells are mainly amplifier/motor cells, not the primary afferent transducers.
- "Stretch-sensitive potassium channels that hyperpolarize hair cells when opened and depolarize them when closed": actual mechanotransduction channels depolarize hair cells when opened (they allow inward K+); the described behavior is opposite to the physiological mechanism.

This explanation confirms the provided correct answer: Mechano-sensitive potassium channels that depolarize modified epithelial cells in the inner ear.

The different chambers of the ear each have a role in conversion of sound energy into action potential firing in auditory axons. Auditory sensory transduction depends on:单项选择题

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