Question

The part of the ear which distinguishes different pitches of sound is

• A. Auditory nerve
• B. Semicircular canal
• C. Organ of corti
• D. Scala media

Answer 1

The correct option is C Organ of corti

Sound waves enter the external auditory canal and cause the tympanic membrane to vibrate. These vibrations are amplified by ear ossicles and are transmitted through oval window to basilar membrane. Vibrations of basilar membrane stimulate the hair cells (mechanoreceptors) of the organ of Corti and nerve impulse is carried to brain. Auditory nerve serves to pass the nerve impulse, generated in hair cells, to brain irrespective of the pitch of the sound.

The three semicircular canals lie at a right angle to each other in vestibular apparatus of the inner ear and are filled with endolymph; this arrangement senses the change in movement (acceleration or deceleration) or position. Semicircular canals are organs of balance, not associated with hearing. Organ of Corti is located in cochlear canal/cochlear duct/scala media and has hair cells on its basilar membrane. Depending upon the pitch (the frequency of sound waves), resonance waves in cochlear fluid cause the particular section of basilar membrane to vibrate. High-frequency sound is detected by hair cells present at the base of cochlea whereas low-frequency sound is detected by hair cells present at the apex of the cochlea.

Therefore, the correct answer is option C.