AEMCA Practice Exam

What does cranial nerve 4 do?

1. Controls rotation of the eye up and down

2. Regulates heart rate

3. Facilitates balance in the inner ear

4. Controls sensation in the arms

The correct answer is: Controls rotation of the eye up and down

Cranial nerve 4, also known as the trochlear nerve, is primarily responsible for innervating the superior oblique muscle of the eye. This muscle plays a crucial role in enabling the downward and inward movement of the eye, which is essential for proper eye coordination, particularly when looking down or reading. Hence, the correct answer highlights its function in controlling the rotation of the eye up and down. The other options pertain to different cranial nerves or functions: regulating heart rate is managed by the vagus nerve, balance is facilitated by the vestibulocochlear nerve within the inner ear, and sensation in the arms is largely governed by the brachial plexus and specific spinal nerves, not cranial nerves. Understanding these distinctions emphasizes the specific role cranial nerve 4 plays in ocular movement.