Which cranial nerve is responsible for autonomic control of the heart, lungs, and GI tract?

• A. Oculomotor (III)
• B. Trigeminal (V)
• C. Vagus (X)
• D. Glossopharyngeal (IX)

Answer: (C)

Autonomic control of the heart, lungs, and GI tract is provided by the parasympathetic output of the vagus nerve. It carries preganglionic parasympathetic fibers from the medulla that synapse near or within the target organs, enabling slowing of the heart rate and conduction, bronchoconstriction, and stimulation of digestive activities like motility and secretions. While other cranial nerves have autonomic roles in different regions (such as pupil constriction with the eye, or parasympathetic influence to the salivary glands), none regulate heart, lungs, and the GI tract as their primary function. Thus, the vagus nerve is the one responsible for this autonomic control.