The inner-ear structure that converts sound vibrations into nerve impulses is the?

• A. Ear
• B. Semicircular canals
• C. Cochlea
• D. Auditory nerve

Answer: (C)

The function being tested is how sound energy is turned into neural signals, a job carried out by the cochlea in the inner ear. When sound waves reach the inner ear, they cause movement of fluid inside the cochlea. This motion bends the hair cells of the organ of Corti, which are the sensory receptors for hearing. The bending opens ion channels, generating electrical signals and releasing neurotransmitters that stimulate the auditory nerve fibers. Those neural impulses are what travel to the brain to be interpreted as sound. The auditory nerve itself transmits these impulses but does not convert the vibrations into signals. The semicircular canals are involved in balance, not hearing, and “ear” is too broad a term for the specific structure responsible for transduction.