Q.(i) Draw a labelled diagram of internal structure of human ear.

The ear converts sound waves into nerve impulses through outer, middle and inner sections, culminating in the cochlea's Organ of Corti.

(i) Structure (as would be shown in a labelled diagram), three regions:

• Outer ear: pinna (external flap that funnels sound) leading into the auditory canal (external auditory meatus), ending at the tympanic membrane (eardrum).
• Middle ear: an air-filled cavity containing three small bones (ossicles) — malleus (hammer), incus (anvil) and stapes (stirrup) — that connect the eardrum to the oval window of the inner ear; also connected to the throat via the Eustachian tube (pressure equalisation).
• Inner ear: a fluid-filled labyrinth containing the coiled cochlea (hearing) and the vestibular apparatus (semicircular canals + utricle/saccule, for balance). Inside the cochlea lies the Organ of Corti, the actual sound receptor, with hair cells resting on the basilar membrane.

(ii) Mechanism of hearing:

1. The pinna collects and funnels sound waves down the auditory canal to the tympanic membrane, causing it to vibrate.
2. These vibrations are transmitted and mechanically amplified through the chain of ossicles (malleus → incus → stapes) to the oval window of the cochlea.
3. Vibration of the oval window sets up pressure waves in the cochlear fluid (perilymph/endolymph), which travel along the basilar membrane.
4. These waves bend the hair cells of the Organ of Corti resting on the basilar membrane; bending of the hair-cell stereocilia opens ion channels, generating a receptor potential. …