Question

In a man, if the abducens nerve is injured then which one of the following functions will be affected?
(a) Movement of the eyeball
(b) Swallowing
(c) Movement of the tongue
(d) Movement of the neck

Answer 1

In humans, the abducens nerve (or abducens nerve) is the sixth cranial nerve (CNVI) responsible for outward gaze, which regulates the action of the lateral rectus muscle.

Complete answer:
- The human abduction nerve is derived from the embryonic pons' basal plate. The outward gaze of the eye is due to this muscle.
- Abducens nerve is an efferent somatic nerve.
- The abducens nerve is a cranial nerve originating from the ventral surface of the medulla oblongata. It is present in the eyeball's lateral rectus muscle.
- It is a motor nerve and it regulates the eyeball's movement.
- Therefore, if a man's abducens nerve is damaged, the eyeball movement will be affected.

Additional information:
- The most frequently affected oculomotor nerve in adults is the sixth cranial nerve.
- A major risk factor for abducens nerve palsy is poorly regulated diabetes mellitus.
- The abducens nerve has the longest intracranial path of any cranial nerve. Ipsilateral eye abduction is largely responsible for it.
- The failure of the abducens nerve to send signals to the lateral rectus results in the abducens nerve paralysis, resulting in the inability to abduct the eye and horizontal diplopia.
- Horizontal diplopia patients complain that two images are side by side.
- Medial rectus contraction (adduction or medial movement) pushes the eye towards the nose. Lateral rectus contraction forces the eye (abduction or lateral movement) away from the nose.
So, the correct answer is ‘(a) Movement of eyeball’.

Note:
- At the intersection of the pons and medulla, the abducens nerve leaves the brainstem, medial to the facial nerve. From this location, it runs upward and forwards to meet the eye.