git hormones

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GIT HORMONES
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OVERVIEW OF GIT HORMONES
We will discuss the following hormones:
-
-
Gastrin
Secretin
CCK
Motilin
Somatostatin
GIP
VIP
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GASTRIN

Produced by G-cells in the stomach.
Functions:
1)
Stimulates the release of
Pepsinogen in the stomach.
HCL
and
2)
Increases gastric motility.
3)
Increases ileal motility.
4)
Relaxes Ileocecal Sphincter.
5)
Induces mass movements in colon [help the
contents moving through GIT on arrival of
new meal in the stomach].
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SECRETIN
It is released from small intestine when stomach
acidic contents come to duodenum.
Functions:
1)
It inhibits gastric emptying to delay the acid
contents of stomach to enter in the duodenum.
2)
It inhibits gastric secretion.
3)
It acts on pancreatic duct to produce large
volume of watery, alkaline NaHCO3 secretion.
4)
It stimulates the secretion of NaHCO3 rich bile
in the liver by acting on the bile ducts.
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CCK (Cholecystokinin)
CCK is released from the duodenum in
response mainly to fat, to a lesser extent to
protein products.
Functions:
1)
Inhibition
stomach
of
motility
and
secretion
of
2)
Stimulates pancreatic acinar cells to secrete
pancreatic enzymes [amylase, lipase,
Trypsinogen, Chymotrypsinogen].
3)
Causes contraction of gall-bladder and
relaxation of sphincter of Oddi.
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MOTILIN
It
is
a
polypeptide
and
secreted
by
Entrochromaffin cells and Mo cells in the
stomach, small intestine and colon.
Functions:
1)
Causes contraction of smooth muscles in
the stomach and intestine.
2)
Increases during inter-digestive state and
controls GIT motility between the meals.
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SOMATOSTATIN

Secreted by D-Cells in pancreatic islets and
by similar D-cells in GIT mucosa.
Functions:
1)
Inhibits secretion of Gastrin, VIP, GIP,
Secretin and Motilin.
2)
Somatostatin secretion is stimulated by
acid in the lumen of intestine.
3)
It acts in a paracrine fashion.
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GIP
[Glucose Dependent Insulinotorphic Peptide]
GIP is released from the duodenum.
Functions:
1) GIP causes release of insulin
(=Insulinotorphic). Insulin causes
uptake and storage of glucose.
2) GIP was called Gastric Inhibitory
Peptide [this role is minimum].

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VIP
[Vasoactive Intestinal Peptide]

VIP is found in nerves in the GIT. VIP is also
found in the brain, blood & autonomic nerves.
Functions:
1)
VIP stimulates intestinal
electrolytes and water.
secretion
of
2)
Relaxation of intestinal smooth muscle
including sphincters.
3)
Inhibition of gastric acid secretion.
4)
VIP potentiates the action of acetylcholine in
salivary glands.
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Ghrelin
 Ghrelin
is secreted by endocrine cells
in the stomach, especially when one is
hungry.
 Ghrelin acts on the hypothalamus to
stimulate feeding. This action
counteracts the inhibition of feeding by
leptin.
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PeptideYY (PYY)
It is released by cells in the intestine after
meals.
 It is a potent feeding inhibitor.
 The amount secreted increases with the
number of calories ingested and especially
when these are derived from proteins rather
than carbohydrates or fats.
 PYY acts on the hypothalamus to suppress
appetite.
 It increases pancreatic exocrine secretion &
bile.

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REFERENCES
Human physiology by Lauralee Sherwood,
seventh edition
 Text book physiology by Guyton &Hall,11th edition
 Text book of physiology by Linda .s contanzo,third
edition

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