What membrane sits above the basilar membrane and serves as a shelf against which the cilia of auditory hair cells move?

• A. Nociceptors
• B. EPSP
• C. Tectorial membrane
• D. IPSP

Answer: (C)

The main concept here is how mechanical vibration from sound is turned into a neural signal in the inner ear. The membrane that sits above the basilar membrane is the tectorial membrane, a gelatinous shelf over the organ of Corti. As the basilar membrane vibrates in response to sound, the organ of Corti moves relative to the tectorial membrane, causing the stereocilia of the hair cells to bend. This deflection opens mechanically gated ion channels at the tips of the stereocilia, leading to receptor potentials and neurotransmitter release onto auditory nerve fibers. The tectorial membrane’s position and contact with the hair bundles enable that precise bending, especially for the outer hair cells whose stereocilia are embedded in it, enhancing sensitivity to sound. In short, the tectorial membrane provides the mechanical interface that the hair cells use to convert motion into electrical signals.