The hair cells of the organ of Corti are arranged with inner and outer hair cells separated by pillar cells. The outer hair cells differ from inner hair cells by which property that is crucial for cochlear amplification?

• A Outer hair cells are solely responsible for sound transduction to the auditory nerve
• B Outer hair cells contain more afferent nerve endings than inner hair cells
• C Outer hair cells respond only to high frequencies above 4 kHz
• D Outer hair cells are electromotile — they change length in response to membrane potential changes (prestin-mediated) ✓

Explanation

Outer hair cells (OHCs) possess electromotility mediated by the motor protein prestin in their lateral wall. When depolarized, OHCs shorten; when hyperpolarized, they elongate — producing mechanical amplification of basilar membrane vibration at the appropriate frequency location. This active process ('cochlear amplifier') enhances sensitivity and frequency selectivity by ~40–60 dB. In contrast, the inner hair cells (IHCs) are the main sensory transducers — they receive ~95% of afferent nerve fibers — while OHCs receive mostly efferent innervation (from the olivocochlear bundle).

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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