Alimentary and Digestive System Practice Test

In gastric motility, control unfolds in three sequential phases that coordinate digestion: preparation, active digestion, and regulation as chyme moves into the intestine. The cephalic phase is driven by the vagus nerve in response to sight, smell, or thought of food, priming the stomach for action. The gastric phase begins once food is present in the stomach; distension and peptide stimuli trigger gastrin release, which together with the direct vagal and local reflex pathways increases gastric secretions and motility to mix and propel contents. The intestinal phase then slows gastric activity to prevent overload, with hormones like secretin and cholecystokinin acting to dampen motility and acid secretion as chyme enters the duodenum.

This combination—cephalic preparation via vagal input, gastric enhancement driven by distension and gastrin, and intestinal inhibition via secretin/CCK—is why the statement describing these three phases is the best answer. The other descriptions misstate how the phases are initiated or regulated, especially the idea that the intestinal phase has no effect and that the cephalic phase is driven exclusively by acids or hormones.