Advanced Health Assessment Practice Exam

What actions are controlled by cranial nerve III?

1. Pupil dilation and eye movement

2. Facial sensations and movements

3. Eyelid raising and pupil constriction

4. Hearing and balance

The correct answer is: Eyelid raising and pupil constriction

Cranial nerve III, also known as the oculomotor nerve, is primarily responsible for a variety of functions related to eye movement and the regulation of pupil size. Specifically, it controls the movement of most of the eye muscles, which include those responsible for elevating the eyelid, moving the eye in different directions, and facilitating pupillary constriction. The ability to raise the eyelid is an important function in maintaining an open and functional visual field. Additionally, this nerve plays a crucial role in accommodating the lens for near vision through its control over cilary muscle contraction, which also contributes to pupil constriction. The other options pertain to functions that are controlled by different cranial nerves. Options related to facial sensations and movements refer to cranial nerve V (trigeminal nerve) and cranial nerve VII (facial nerve), respectively. Hearing and balance are functions associated with cranial nerve VIII (vestibulocochlear nerve). Pupil dilation involves the sympathetic nervous system and is mediated by different pathways, thus is not under the control of cranial nerve III. Therefore, focusing on eyelid raising and pupil constriction accurately captures the key functions of cranial nerve III.