Which phase of gastric motility is triggered by anticipation of food and what neural pathway mediates it?

• A. Cephalic phase is mediated by sympathetic input
• B. Cephalic phase (vagal activity) prepares the stomach; gastric phase (gastrin and distension) increases activity; intestinal phase (secretin/CCK) dampens gastric activity.
• C. Cephalic phase triggered by acid only
• D. Cephalic phase unaffected by neural input

Answer: (B)

Anticipation of food triggers the cephalic phase, a neural drive that uses the parasympathetic system via the vagus nerve to the stomach. This vagal activity primes the stomach by increasing motility and stimulating secretion, so the stomach is ready for digestion. As the stomach fills, the gastric phase takes over, driven by distension and gastrin release from G cells, which further enhances contractions and acid secretion. When chyme enters the small intestine, the intestinal phase comes into play, with hormones like secretin and cholecystokinin dampening gastric activity to modulate digestion. The sympathetic pathway would inhibit GI activity, not drive it, and the cephalic phase is not triggered by acid or entirely independent of neural input.