Gastrin is released by the stomach due to distension and the presence of foods. Histamine is released locally by ECL cells. Both increase gastric acid secretions. Somatostatin, released in the pyloric antrum, decreases gastric acid secretions. It has both local and systemic effects. Motilin stimulates GI motility.
Lipids and carbohydrates in the duodenum stimulate secretion of CCK (cholecystokinin) and GIP/GLP-1. CCK stimulates the pancreas to produce digestive enzymes, the liver to produce bile, and the gallbladder to secrete bile. GIP and GLP-1 stimulate insulin release in preparation for an anticipated surge of blood glucose. Decreased pH in the duodenum, as a result of the incoming acidic chyme, stimulates secretin release. Secretin inhibits secretion of gastric acid and stimulates pancreatic bicarbonate secretion.
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