REGULATION OF DIGESTION

By: Safana Sadiq

The digestive system is controlled by both: Nerves, and

Hormones

Autonomic Nervous System

SNS PNS

Neuronal control of digestion

Digestive system activity

Digestive system activity

Sympathetic nerves that regulate digestion are:

The greater splanchnic nerves

The lumbar splanchnic nerves, and

The sacral splanchnic nerves

The parasympathetic nerve that regulates

digestion are the vagus nerves.

Hormones that control digestion are:

Gastrin

Secretin

Cholecystokinin

Glucose insulinotropic peptide (GIP)

Stimulates gastric juice secretion

Stimulates smooth muscle contraction

Relaxation of pyloric sphincter

Effects of gastrin

Stimulates bicarbonate secretion

Stimulates bile production

Inhibits gastric juice secretions and gastric motility

Effects of secretin

Stimulates bile release

Stimulates pancreatic juice secretion

Relaxation of the hepatopancreatic ampulla and opening of hepatopancreatic sphincter

Effects of cholecystokinin

Stimulates the pancreas to begin release of

insulin

Effects of GIP

Cephalic phase

Gastric phase

Intestinal phase

The 3 phases of digestive regulation

Neuronal response:

Stimuli that arouse digestion relayed to hypothalamus

Nerve impulse initiated in vagus nerve

Impulse innervates nerve network of GI tract

Contraction of sm ms & secretion of gastric juice promoted

Cephalic Phase

The stimuli that initiates gastric phase includes:

Distension of the stomach

Low acidity

Presence of peptides

Gastric Phase

Neural response: gastric juice secretion &

smooth muscle contraction promoted

Hormonal response: gastrin production promoted

General effect: stomach and small intestine prepare for digestion of chyme , and gastric emptying is promoted

Gastric Phase

Neural response:

gastric secretion & gastric motility are inhibited Intestinal secretion, sm ms contraction, bile &

pancreatic juice production are promoted

Intestinal Phase

Hormonal response: production of secretin,

CCK & GIP is promoted

General effects : gastric emptying is retarded to allow adequate time for digestion in the SI. And intestinal digestion and motility are promoted.

Intestinal Phase

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Reference