Which structure in the cochlea contains hair cells that detect sound?

• A. Organ of Corti
• B. Basilar membrane
• C. Auditory nerve
• D. Cochlear nuclei in the brainstem

Answer: (A)

The ability to detect sound is carried by hair cells that reside in the organ of Corti within the cochlea. The organ of Corti sits on the basilar membrane and contains inner and outer hair cells with hair-like projections called stereocilia. When sound sets the basilar membrane in motion, it bends those stereocilia, opening ion channels and converting mechanical energy into electrical signals that the brain can interpret as sound. That makes the organ of Corti the sensory structure that detects sound.

The basilar membrane itself plays a crucial role in separating frequencies by how much it moves at different locations, but it is not where the hair cells reside. The auditory nerve then carries the signals from those hair cells toward the brain, and the cochlear nuclei in the brainstem are higher-processing stations, not the site of sound detection.