The medial olivocochlear bundle provides efferent innervation primarily to which cells of the organ of Corti, and what is the functional consequence of activating these fibres?

• A Outer hair cells, reducing cochlear amplifier gain and improving discrimination in noise ✓
• B Inner hair cells, increasing auditory afferent firing rate
• C Inner hair cells, producing electromotility of the basilar membrane
• D Outer hair cells, generating the endocochlear potential

Explanation

Medial olivocochlear fibres synapse directly on outer hair cells, causing them to shorten and reduce basilar membrane motion, which protects against acoustic trauma and sharpens signal detection in background noise. Inner hair cells receive almost all afferent innervation but only sparse lateral efferent input. The endocochlear potential is generated by the stria vascularis, not by hair cells, eliminating option D.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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