GI hormones Flashcards
(29 cards)
What must be done to consider a molecule a GI hormone?
1) released after physio stim causing action
2) effects independent of nervous system
3) can be administered exogenously
4) chemically ID’ed
what are the 5 GI hormones?
secretin; gastrin; CCK; GIP; motilin
What is the source of gastrin?
G cells of gastric antrum
source and stimulus of CCK?
I cells of duodenum and jejunum
=> fatty acids; monoglycerides;
=> small peptides and amino acids
source and stimulus of secretin ?
S cells of duodenum
=> decrease in duodenal lumen pH
source and stimulus of GIP
K cells of duodenum and jejunum
=> glucose, fatty acids, amino acids
source and stimulus of motilin
enterochromaffin cells in duodenum and jejunum
=> absence of food for >2hours
what stimulates G cells to produce gastrin?
small peptides, amino acids; Ca+ in lumen of stomach
=>vagus via GRP
=> stomach distension
=> inhibited by: H+ in lumen of antrum
Actions of gastrin?
- increase HCl secretion by parietal cells
- trophic effects on GI mucosa
- increase pepsinogen secretion by chief cells
- increase histamine secretion by ECL cells
actions of CCK
- stimulates gallbladder contraction and relaxes sphincter of oddi
- increases pancreatic enzyme secretion
- augments secretin-induced stimulation of pancreatic HCO3
- inhibits gastric emptying
- trophic effect on exocrine pancreas/gallbladder
actions of secretin
- increase pancreatic HCO3 secretion (neutralizes H+)
- trophic effect on exocrine pancreas
- increase bile production
- decrease gastric acid secretion
actions of GIP
- increase insulin release
* decrease gastric acid secretion
action of motilin
initiates MMC motility pattern in stomach and small intestine
What are 2 hormonal tumors of the GI tract?
gastrinoma (ZE syndrome);
VIPoma
What is ZE syndrome?
non-Beta islet cell pancreatic tumor produces gastrin
=> increase in gastric acid secretion and development of peptic ulcer disease
What is VIPoma?
tumor of non-alpha, non-Beta islet cells of pancreas that secretes VIP
=> watery diarrhea
What are the paracrine/neurocrine hormones of GI?
somatostatin; histamine; VIP; GRP; pancreatic polypeptide; enteroglucagon
Source and stimulus of somatostatin
D cells throughout GI tract
=> decrease in luminal pH
Source and stimulus of histamine
Enterochromaffin cells
=> gastrin; ACh
Source and stimulus of VIP
neurons in GI tract
=> vagal stimulation; intestinal distension
Source and stimulus of GRP
vagal nerve endings;
=> cephalic stimulation; gastric distension
Source and stimulus of pancreatic polypeptide
F cells of pancreas & small intestine
=> protein, fat, glucose in lumen
Source and stimulus of enteroglucagon
L cells of intestine
actions of somatostatin
- decrease gallbladder contraction; pancreatic secretion
- decrease gastric acid & pepsinogen secretion
- decrease small intestinal fluid secretion
- decrease ACh release from myenteric plexus & decreases motility
- decrease alpha-cell release of glucagon and Beta-cell release of insulin in pancreatic islet cells
