GI hormones

Question 1

What must be done to consider a molecule a GI hormone?

Answer 1

1) released after physio stim causing action
2) effects independent of nervous system
3) can be administered exogenously
4) chemically ID’ed

Question 2

what are the 5 GI hormones?

Answer 2

secretin; gastrin; CCK; GIP; motilin

Question 3

What is the source of gastrin?

Answer 3

G cells of gastric antrum

Question 4

source and stimulus of CCK?

Answer 4

I cells of duodenum and jejunum

=> fatty acids; monoglycerides;
=> small peptides and amino acids

Question 5

source and stimulus of secretin ?

Answer 5

S cells of duodenum

=> decrease in duodenal lumen pH

Question 6

source and stimulus of GIP

Answer 6

K cells of duodenum and jejunum

=> glucose, fatty acids, amino acids

Question 7

source and stimulus of motilin

Answer 7

enterochromaffin cells in duodenum and jejunum

=> absence of food for >2hours

Question 8

what stimulates G cells to produce gastrin?

Answer 8

small peptides, amino acids; Ca+ in lumen of stomach
=>vagus via GRP
=> stomach distension
=> inhibited by: H+ in lumen of antrum

Question 9

Actions of gastrin?

Answer 9

• increase HCl secretion by parietal cells
• trophic effects on GI mucosa
• increase pepsinogen secretion by chief cells
• increase histamine secretion by ECL cells

Question 10

actions of CCK

Answer 10

• 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

Question 11

actions of secretin

Answer 11

• increase pancreatic HCO3 secretion (neutralizes H+)
• trophic effect on exocrine pancreas
• increase bile production
• decrease gastric acid secretion

Question 12

actions of GIP

Answer 12

• increase insulin release

* decrease gastric acid secretion

Question 13

action of motilin

Answer 13

initiates MMC motility pattern in stomach and small intestine

Question 14

What are 2 hormonal tumors of the GI tract?

Answer 14

gastrinoma (ZE syndrome);

VIPoma

Question 15

What is ZE syndrome?

Answer 15

non-Beta islet cell pancreatic tumor produces gastrin

=> increase in gastric acid secretion and development of peptic ulcer disease

Question 16

What is VIPoma?

Answer 16

tumor of non-alpha, non-Beta islet cells of pancreas that secretes VIP
=> watery diarrhea

Question 17

What are the paracrine/neurocrine hormones of GI?

Answer 17

somatostatin; histamine; VIP; GRP; pancreatic polypeptide; enteroglucagon

Question 18

Source and stimulus of somatostatin

Answer 18

D cells throughout GI tract

=> decrease in luminal pH

Question 19

Source and stimulus of histamine

Answer 19

Enterochromaffin cells

=> gastrin; ACh

Question 20

Source and stimulus of VIP

Answer 20

neurons in GI tract

=> vagal stimulation; intestinal distension

Question 21

Source and stimulus of GRP

Answer 21

vagal nerve endings;

=> cephalic stimulation; gastric distension

Question 22

Source and stimulus of pancreatic polypeptide

Answer 22

F cells of pancreas & small intestine

=> protein, fat, glucose in lumen

Question 23

Source and stimulus of enteroglucagon

Answer 23

L cells of intestine

Question 24

actions of somatostatin

Answer 24

• 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

Question 25

actions of histamine

Answer 25

* increase gastric acid secretion directly | - potentiates gastrin and vagal stimulation

Question 26

actions of VIP

Answer 26

* relaxation of intestinal smooth muscle, including sphincters * increase pancreatic HCO3 secretion * stimulates intestinal secretion of electrolytes and H20

Question 27

actions of GRP

Answer 27

*stimulates gastrin release from G cells

Question 28

actions of pancreatic polypeptide

Answer 28

-decrease in pancreatic secretion

Question 29

actions of enteroglucagon

Answer 29

- decrease gastric and pancreatic secretions | - increase insulin release