Question

What are the four lobes and what nerve impulses are they most associated with?

There are three cranial nerves that serve the muscles of the eye. What are they? Identify each, and describe how they work.

Answer 1

LOBES OF BRAIN:​​​​​​

1. Frontal lobe
2. Parietal lobe
3. Temporal lobe
4. Occipital lobe

1.Frontal lobe:

Lies anterior to central sulcus and above posterior ramus of lateral sulcus.

It contributes the motor areas which send motor nerve impulses to entire body.

2.Parietal lobe:

Lies behind central sulcus and infront of upper part of first imaginary line. Below it is bounded by posterior ramus of lateral sulcus and second imaginary line.

It is associated with sensory areas which receive sensory nerve impulses from entire body.

3.Temporal lobe:

Lies below posterior ramus of lateral sulcus and second imaginary line.

This lobe is also known as auditory cortex as it receives auditory impulses from the ear.

4.Occipital lobe:

Lies behind vertical line joining parieto-occipital sulcus and pre-occipital notch.

This lobe is also known as visual cortex as it receives visual impulses from the eyes.

CRANIAL NERVES SUPPLYING EXTRAOCULAR MUSCLES OF EYE:

1.Oculomotor nerve (third cranial nerve)

2.Trochlear nerve (fourth cranial nerve)

3.Abducent nerve (sixth cranial nerve)

1. Oculomotor nerve arises from cerebral peduncle medial aspect and supplies superior rectus, inferior rectus, inferior oblique and medial rectus muscles which are involved in movements of eye ball.

In addition, it also supplies levator palpebrae superioris, dilator pupillae, constrictor pupillae and ciliary muscle.

2. Trochlear nerve arises from dorsal aspect of midbrain and supplies superior oblique muscle which is the only depressor of eye ball during adduction.

3. Abducent nerve arises at ponto-medullary junction above the pyramid of medulla and it supplies lateral rectus muscle of eyeball which causes abduction of eyeball.