Question

With reference to the human ear, answer the question that follows:

(i) Give the technical term for the structure found in the inner ear.

(ii) Name the three small bones present in the middle ear. What is the biological term for them collectively?

(iii) Name the part of the ear, associated with (1) static balance (2) hearing (3) dynamic balance.

(iv) Name the nerve which transmits messages from the ear to the brain.

Answer 1

(i) Inner ear:

1. The inner ear is located next to the middle ear.
2. Labyrinth is the technical term for the structure found in the inner ear.
3. It has two parts bony labyrinths and membranous labyrinths.
4. A bony labyrinth is located in a cavity, within the temporal bone.
5. Membranous labyrinths consist of - a vestibule, three semicircular canals, and a cochlea.
6. Sometimes, the inner is considered a membranous labyrinth.
7. The structures found in the inner ear are - (a) Vestibule, (b) semicircular canals, and (c) the Cochlea.

(ii) Ear ossicles or Auditory ossicles:

1. The three bones (malleus, incus, and stapes) are articulated to form a chain for the transmission of sound from the external ear to the inner ear.
2. Auditory ossicles is the collective name of the three bones in the middle ear.

(iii)

Static Equilibrium:

1. Static equilibrium involves the vertical or horizontal movement of the head.
2. Utricle, saccule, and the ampullae of the semicircular canals contain balance receptors (they are very sensitive to the gravity)
3. Displacement of otolith (granular endolymph of vestibule) within the utricle and the saccule maintain the static equilibrium.
4. Static equilibrium or static balance is maintained by utricle and saccule.

Hearing:

1. The cochlea is responsible for hearing. The cochlea is a highly coiled canal of the inner ear. It appears like a snail.
2. The auditory nerve carries impulses from the cochlea to the brain.
3. The auditory nerve is connected to the cochlea.

Dynamic equilibrium:

1. It involves the maintaining of proper head position at the time of rotational movement.
2. When the rotation occurs, the fluid of semicircular canals pushes against the cupula (the conical gelatinous structure). It causes the bending of the cilia of the receptor cells and this creates impulses to the sensory nerve.
3. The dynamic equilibrium is maintained by semicircular canals.

(iv) Auditory nerve:

1. The auditory nerve is the VIII^th cranial nerve. It is a sensory nerve.
2. The audio sensation is transmitted to the brain (cerebrum) by the auditory nerve.
3. The auditory nerve transmits auditory messages from the ear to the brain.