What is the function of the nucleus ambiguus?

• A. Somatic motor - active/voluntary movement
• B. Autonomic parasympathetic
• C. Visceral sensory
• D. Proprioception

Answer: (A)

Nucleus ambiguus contains motor neurons that innervate the striated muscles of the pharynx, larynx, and upper esophagus through cranial nerves IX and X. These muscles are involved in swallowing and vocalization, and they are under voluntary control. That makes the nucleus ambiguus primarily a somatic motor (active/voluntary) system.

It isn’t autonomic parasympathetic, because the parasympathetic outflows to the heart, glands, and smooth muscle come from other nuclei (like the dorsal motor nucleus of the vagus and the inferior salivatory nucleus). It also isn’t a sensory center, since it does not carry visceral sensory information or proprioceptive input—that information goes to different sensory nuclei and pathways.