Emergency Medical Technician (EMT) Intermediate Practice Exam

Which nerve is responsible for the movement of the eyeballs and upper eyelid?

1. Trochlear nerve

2. Optic nerve

3. Oculomotor nerve

4. Abducens nerve

The correct answer is: Oculomotor nerve

The movement of the eyeballs and the upper eyelid is primarily controlled by the oculomotor nerve. This cranial nerve is responsible for several key functions, including innervating most of the extraocular muscles that allow the eye to move in various directions. It also innervates the levator palpebrae superioris muscle, which is responsible for lifting the upper eyelid, facilitating its movement. In contrast, the trochlear and abducens nerves are primarily responsible for specific eye movements but do not control the upper eyelid. The trochlear nerve specifically innervates the superior oblique muscle, allowing the eye to move downward and outward. The abducens nerve innervates the lateral rectus muscle, enabling lateral movement of the eyeball. The optic nerve, on the other hand, is primarily responsible for transmitting visual information from the retina to the brain and does not control any movements. Thus, the oculomotor nerve is correctly identified as the cranial nerve responsible for both moving the eyeballs and controlling the upper eyelid.