Describe the three phases of gastric regulation. Be sure to include the appropriate local, neural and hormonal responses for each phase

Answer 1

The first phase is the cephalic phase. It begins with the thoughts, sight, or smell of food. This phase is directed by the CNS and increases vagus nerve stimulation of the submucosal neural plexus. This increases mucus, acid and gastrin production. The next phase, the gastric phase, begins when food enters the stomach and both stretch receptors and chemoreceptors are stimulated. A local response increases histamine release. The neural response increases activity of the myenteric and submucosal neural plexus to increase motility and secretions. The hormonal response is mediated by the release of gastrin to increase motility and secretions. The final phase, the intestinal phase, begins as chyme enters the duodenum. Distension of the duodenum stimulates stretch receptors to begin the enterogastric reflex which limits the amount of chyme that enters the duodenum. The hormonal response includes release of CCK, GIP and secretin to increase bile release and pancreatic juice release for intestinal digestion and to limit gastrin release.