Question

How does ear convert sound waves into neural impulses, which are sensed and processed by the brain enabling us to recognise a sound ?

Answer 1

Part 1: Introduction of ear and its functions
The ear is a sensory organ responsible for hearing and maintenance of balance (dynamic as well as static).

• It responds to sound waves and hence gives the sense of hearing.
• Organ of corti (organ of hearing) and vestibular apparatus (balance maintaining organ), it detects the sound waves and postural changes respectively.
• It then transfers this information to the higher centers of the brain to be processed.
• Hence the brain perceives the sound waves, changes in posture while at rest or while moving.

Part 2: Mechanism of Hearing

1. The pinna of the external ear collects sound waves which pass through the external auditory meatus all the way to the eardrum.
2. These vibrations are passed from the eardrum to the malleus, incus and stapes of the middle ear which causes an increase in the frequency of the vibrations.
3. The vibrations furthermore are passed to the cochlea of the inner ear through the oval window.
4. These vibrations in the endolymph of the cochlea cause vibrations to be induced in the basilar membrane, which in turn cause the sensory hair of the organ of corti to vibrate.
5. The receptor hair cells force themselves against the tectorial membrane, converting sound energy to a nerve impulse or action potential.
6. This nerve impulse is transmitted to the auditory cortex of the brain, where the impulse is evaluated and analyzed causing the sound to be recognized.