What does the oculomotor nucleus control?

• A. Eyeball/eye movement
• B. Facial expression
• C. Tongue movement
• D. Shoulder elevation

Answer: (A)

The oculomotor nucleus specializes in moving the eye and lifting the eyelid. It provides motor signals to most of the extraocular muscles that turn the eyeball (medial, superior, and inferior rectus, and inferior oblique) as well as to the levator palpebrae superioris, which raises the upper eyelid. This is why it directly controls eyeball movement and eyelid elevation.

In addition, the oculomotor nerve carries parasympathetic fibers that help constrict the pupil and adjust the lens, but those preganglionic fibers originate from a separate nucleus (not the oculomotor nucleus itself). The other options are controlled by different nerves: facial expression by the facial nerve, tongue movement by the hypoglossal nerve, and shoulder elevation by the spinal accessory nerve.