The facial motor nucleus is associated with which function?

• A. Muscles of facial expression
• B. Muscles of mastication
• C. Eye movements
• D. Pharyngeal constrictors

Answer: (A)

This question tests which group of muscles the facial motor nucleus controls. The facial motor nucleus is the motor nucleus of the facial nerve (cranial nerve VII) and it sends lower motor neuron fibers to all the muscles of facial expression. That means it innervates muscles like the frontalis (forehead), orbicularis oculi (around the eye), and muscles around the mouth, enabling facial expressions and movements of the face.

Other motor groups map to different functions: muscles of mastication are driven by the trigeminal motor nucleus, eye movements by the oculomotor, trochlear, and abducens nuclei, and the pharyngeal constrictors are controlled by nuclei associated with the glossopharyngeal and vagus nerves. So the facial motor nucleus best aligns with muscles of facial expression.