Neural Regulation
Distention of the duodenum by the presence of chyme causes the Enterogastric Reflex. This is initiated by stretch receptors located in the duodenal wall which send nerve impulses to the medulla oblongata where parasympathetic stimulation is inhibited and sympathetic are stimulated. The result: gastric motility is inhibited and there is an increase in contraction of the pyloric sphincter decreasing gastric emptying.
Hormonal Regulation
This part is regulated by 2 major hormones both secreted by the small intestine: Cholecystokinin (CCK) secreted by CCK cells of the small intestine in response to chyme containing partially digested proteins, fatty acids, and triglycerides. CCK stimulates the secretion of bile and pancreatic juice rich in digestive enzymes. There are several other functions of CCK. Acidic chyme entering the duodenum stimulates the release of Secretin from the S cells of the small intestine. This stimulates the flow of pancreatic juice rich in buffer substance to buffer the acidic chyme. Secretin inhibits the secretion of gastric juice (slows the production of acid in the stomach), promotes normal growth and maintenance of the pancreas and enhances the effects of CCK.
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