Describe the regulations of the cephlic gasrtic and the intestinal phase of gastric secretion?

Question

Describe the regulations of the cephlic gasrtic and the intestinal phase of gastric secretion?

Answer 1

The cephalic phase consists of reflexes initiated by sensory receptors in the head.  (Thoughts of food, smell, taste) The cephalic phase stimulates gastric secretion and motility.

The gastric phase begins when food enters the stomach.  When the stomach walls are distended or when pH increases because proteins have entered the stomach and buffered some of the stomach acid, the stretch receptors and chemoreceptors are activated resulting in waves of peristalsis and continual flow of gastric juice.

   Chemoreceptors and stretch receptors stimulate the ANS to release acetylcholine which stimulates the release of gastrin by G cells.  Gastrin stimulates growth of the gastric glands and secretion of large amounts of gastric juice. It also strengthens contraction of the lower esophageal sphincter, increases motility of the stomach, and relaxes the pyloric and ileocecal sphincters.   Acetylcholine released by parasympathetic fibers and gastrin secreted by G cells stimulate parietal cells to secrete more HCl when histamine is present.

The intestinal phase is due to activation of receptors in the small intestine.  When partially digested food enters the small intestine, it triggers the enterogastric reflex and the secretion of gastric inhibitory peptide (GIP), secretin, and cholecystokinin (CCK) by the intestinal mucosa. The effect is inhibition of gastric secretion.

Answer 2

Cephalic- occurs before food enters the digestive system. thought/sight of food triggers Vagus nerve to increase production of saliva by salivary glands.

Intestinal- occurs when food leaves the stomach thru pyloric valve and enters the duodenum. the presence of chyme stimulates the production of intestinal gastrin to digest the food.