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Gastrointestinal Physio
Hormones, Motility, Cell types
43
Physiology
Professional
04/20/2011

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Cards

Term
Gastrin
Definition

Increases H+ secretion by parietal cells

Stimulates growth of gastric mucosa by stimulating synthesis of RNA and new protein

Term
G cells
Definition
Secrete Gastrin, located in gastric antrum
Term
Signals that stimulate Gastrin secretion
Definition

small peptides and amino acids in stomach lumen - phenylalanine and tryptophan

Distention of the stomach

Vagal stimulation by gastrin-releasing peptide (GRP)

Term
Somatostatin
Definition
Inhibits Gastrin Release
Term
Zollinger-Ellison syndrome
Definition
gastrinoma, occurs when gastrin is secreted by non-beta-cell tumors of the pancreas
Term
CCK
Definition

stimulates contraction of bladder and relaxation of sphincter of Oddi

stimulates pancreatic enzyme secretion

potentiates secretin-induced stimulation of pancreatic HCO3- secretion

Stimulates growth of the exocrine pancreas

Inhibits gastric emptying to allow more time for intestinal digestion and absorption

Term
CCK Secretion stimulation
Definition

released from I cells of the duodenal and jejunal mucosa

Small peptides and amino acids

Fatty acids and monoglycerides

Triglycerides DO NOT stimulate secretion

Term
Secretin
Definition

actions are coordinated to reduce the amount of H+ in the lumen of the small intestine

Stimulates pancreatic HCO3- secretion and increases growth of exocrine pancreas

Stimulates HCO3- and H2O secretion by the liver, and increases bile production

Inhibits H+ secretion by gastric parietal cells

Term
Secretin stimulation
Definition

released by S cells of the Duodenum in response to:

H+ in the lumen of the duodenum

Fatty acids in the lumen of the duodenum

Term
GIP
Definition

Stimulates insulin release from pancreas

Inhibits H+ secretion by gastric parietal cells

Term
GIP stimulation
Definition

secreted by duodenum and jejunum

only GI hormone that is released in response to fat, protein, and carbohydrate

stimulated by fatty acids, amino acids, and orally administered glucose

Term
Paracrines
Definition

released from endocrine cells 

diffuse over short distances to act on target cells located in the GI tract

Somatostatin and Histamine

Term
Somatostatin
Definition

secreted by cells throught GI tract in response to H+ in lumen. 

Inhibited by vagal stimulation

inhibits the release of all GI hormones

inhibits gastric H+ secretion

Term
Histamine
Definition

secreted by mast (ECL) cells 

increases gastric H+ secretion

Term
Neurocrines
Definition

synthesized in neurons of the GI tract, moved by axonal transport down the axon and released by action potentials in the nerves

diffuse across synaptic cleft to target cell

vasoactive intestinal peptide (VIP), GRP (bombesin), and enkephalins

Term
VIP
Definition

produces relaxation of the GI smooth muscle, including LES

stimulates pancreatic HCO3- secretion and inhibits gastric H+ secretion

 

Term
GRP (bombesin)
Definition

released from vagus nerves that innervate the G cells

stimulates gastrin release from G cells

Term
Enkephalins (met-enkephalin and leu-enkephalin)
Definition

secreted from nerves in the mucosa and smooth muscle 

stimulate contraction of GI smooth muscle

inhibit intestinal secretion of fluid and electrolytes

Term
Achalasia
Definition
when LES does not relax during swallowing and food accumulates in esophagus
Term
Parietal Cells
Definition

Body (fundus)

Secrete HCl and Intrinsic Factor

Term
Parietal Cell stimulation
Definition

Gastrin

Vagal stimulation (ACh)

Histamine

Term
Chief Cells
Definition

Body (fundus)

Secrete Pepsinogen (converted to pepsin at low pH)

Term
Chief Cell Stimulation
Definition
Vagal Stimulation (ACh)
Term
G Cell
Definition

Antrum

Secrete Gastrin

Term
G cell stimulation
Definition

Vagal stimulation (via GRP)

Small peptides

Inhibited by somatostatin

Inhibited by H+ in stomach

Term
Mucous cells
Definition

Antrum

Secrete mucous and pepsinogen

Term
Mucous cell stimulation
Definition
Vagal stimulation (ACh)
Term
ACh Receptor on Parietal Cell
Definition

M3

Blocked by atropine

Term
Gastrin receptor on parietal cell
Definition

CCKb

second messenger is IP3/Ca2+

Term
Histamine Receptor on parietal cell
Definition

H2

coupled to adenylyl cyclase via Gs protein

second messenger is cAMP

Cimetidine inhibits binding to H2 receptor

Term
Somatostatin action
Definition

direct pathway binds to receptor on parietal cell coupled with adenylyl cyclase via Gi protein decreasing cAMP levels antagonizing histamine

indirect pathway inhibits release of histamine and gastrin

Term
Drugs that block H+ secretion
Definition

Atropine - muscarinic receptors blocked

Cimetidine - blocks H2 receptors

Omeprazole - proton pump inhibitor

Term
composition of Pancreatic secretions
Definition

Isotonic

High flow rates Na+ and HCO3-

low flow rates Na+ and Cl-

Term
cystic fibrosis
Definition

disorder of pancreatic secretion

defect in CFTR channels

associated with a deficiency in pancreatic enzyme causing malabsorption and steatorrhea

Term
Primary Bile Acids
Definition

Cholic acid

chenodeoxycholic acid

Term
Secondary Bile Acids
Definition

Deoxycholic acid

Lithocholic acid

Term
Lactase degrades Lactose to
Definition
glucose and galactose
Term
Trehalase degrades trehalose to
Definition
glucose
Term
sucrase degrades sucrose to
Definition
glucose and fructose
Term
Enterokinase
Definition
brush border enzyme that activates trypsinogen to trypsin
Term
Trypsin
Definition

converts chymotrypsinogen

proelastase

procaboxypeptidase A and B

Trypsinogen to trypsin

Term
Pancreatic Lipases
Definition

cholesterol ester hydrolase

phospholipase A2

Term
Causes of steatorrhea - malabsorption of lipids
Definition

pancreatic diseas

hypersecretion of gastrin

ileal resection

bacterial overgrowth

decreased number of intestinal cells

failure to synthesize apoprotein B

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