Which sequence correctly describes the pathway by which sound becomes a neural impulse?

• A. Sound waves are funneled to the ear; ear drum vibrates; ossicles vibrate; vibration passes to the round window; organ of Corti converts to a neural impulse; auditory nerve carries to the brain.
• B. Sound waves are funneled to the ear; ossicles vibrate; ear drum vibrates; round window vibrates; the auditory nerve carries signals to the brain.
• C. Sound waves are funneled to the ear; eardrum vibrates; ossicles vibrate; vibration passes to the round window; organ of Corti converts to a neural impulse; auditory nerve carries to the brain.
• D. The brain interprets sound without any peripheral steps.

Answer: (C)

The sequence follows how a sound wave becomes a neural signal: sound waves are collected by the outer ear and funneled toward the eardrum, causing the eardrum to vibrate. This mechanical energy is then transmitted and amplified by the small middle-ear bones (ossicles). The vibration moves the fluids in the inner ear through the window on the cochlear side, with the round window providing a pressure release as the fluid shifts. The movement of the cochlear fluids sets the basilar membrane in motion, bending the hair cells in the organ of Corti. Those hair cells convert the mechanical energy into neural impulses, which are carried by the auditory nerve to the brain for interpretation. The brain alone cannot interpret sound without these peripheral steps.