Which cranial nerve impacts digestion through parasympathetic control?

The vagus nerve, which is cranial nerve ten, plays a vital role in the autonomic nervous system, particularly in parasympathetic control of bodily functions. It innervates a broad range of organs, including the heart, lungs, and digestive tract. Specifically, the vagus nerve is responsible for stimulating digestive processes such as the release of digestive enzymes, gastric motility, and regulating the rate of gastric emptying. Its parasympathetic action promotes rest and digest functions, contrasting with the sympathetic nervous system’s fight-or-flight response.

In contrast, while the olfactory, facial, and optic nerves have their own essential functions related to smell, taste, and vision respectively, they do not have a direct role in the control of digestion or the parasympathetic nervous system. The olfactory nerve is involved in the sense of smell, the facial nerve primarily handles taste sensation and facial expressions, and the optic nerve is responsible for vision. Thus, the vagus nerve is the clear choice as it directly influences digestive health and function through its extensive parasympathetic connections.