Which cranial nerves have primarily motor function?

• A. V, VII, IX, X
• B. III, IV, VI, XI, XII
• C. I, II
• D. II, III

Answer: (B)

Cranial nerves that are primarily motor are those whose main job is to move muscles rather than carry sensory information. The ones that fit this description are the nerves that move the eyes and those that control neck and tongue muscles: the oculomotor, trochlear, abducens, accessory, and hypoglossal nerves.

The oculomotor nerve drives most of the eye’s movements and eyelid elevation, and it also constricts the pupil. The trochlear nerve controls the superior oblique muscle, and the abducens nerve moves the lateral rectus. The accessory nerve supplies the sternocleidomastoid and trapezius muscles to move the head and shoulders, while the hypoglossal nerve moves the tongue.

Other cranial nerves have significant sensory roles or mixed functions. Purely sensory ones include the olfactory and optic nerves, while several nerves are mixed, carrying both motor and sensory (and sometimes autonomic) components, such as the trigeminal, facial, glossopharyngeal, and vagus nerves.

So, the nerves with primarily motor function are the oculomotor, trochlear, abducens, accessory, and hypoglossal nerves.