GI - Physiology (GI Regulatory substances)

Question 1

What cells are the source of cholecystokinin? Where in the GI system are these cells found?

Answer 1

I cells (duodenum, jejunum)

Question 2

What cells are the source of gastrin? Where in the GI system are these cells found?

Answer 2

G cells (antrum of stomach)

Question 3

What cells are the source of glucose-dependent insulinotropic peptide? Where in the GI system are these cells found?

Answer 3

K cells (duodenum, jejunum)

Question 4

Where in the GI system is Motilin found?

Answer 4

Small intestine

Question 5

What cells are the source of secretin? Where in the GI system are these cells found?

Answer 5

S cells (duodenum)

Question 6

What cells are the source of somatostatin? Where in the GI system are these cells found?

Answer 6

D cells (pancreatic islets, GI mucosa)

Question 7

In what general structure(s) is Vasoactive intestinal polypeptide (VIP) found? Give 3 areas in the body in which it is found in this (these) structure(s).

Answer 7

Parasympathetic ganglia in sphincters, gallbladder, and small intestine

Question 8

What are the 4 actions of cholecystokinin (CCK)?

Answer 8

(1) Increase pancreatic secretion (2) Increase gallbladder contraction (3) Decrease gastric emptying (4) Increase sphincter of Oddi relaxation

Question 9

What 2 factors regulate cholecystokinin, and how?

Answer 9

Increased by fatty acids, amino acids

Question 10

What does CCK act on to cause pancreatic secretion?

Answer 10

CCK acts on neural muscarinic pathways to cause pancreatic secretion

Question 11

What are the 3 actions of gastrin?

Answer 11

(1) Increase gastric H+ secretion (2) Increase growth of gastric mucosa (3) Increase gastric motility

Question 12

What regulation factors increase versus decrease gastrin? Note: There are 4 factors for increasing gastrin.

Answer 12

INCREASE: by stomach distention/alkalinization, amino acids, peptides, vagal stimulation; DECREASE: by stomach pH < 1.5

Question 13

In what syndrome is gastrin markedly elevated?

Answer 13

Markedly elevated in Zolinger-Ellison syndrome

Question 14

Chronic use of what medication increases gastrin? What other 2 substances are potent stimulators of gastrin?

Answer 14

Increased by chronic PPI use; Phenylalanine and Tryptophan are potent stimulators

Question 15

What are the 2 categories of action by glucose-dependent insulinotropic peptide? What occurs in each category?

Answer 15

EXOCRINE: decrease gastrin H+ secretion; ENDOCRINE: increase insulin release

Question 16

What 3 factors regulate glucose-dependent insulinotropic peptide, and how?

Answer 16

Increased by fatty acids, amino acids, oral glucose

Question 17

What is another name for glucose-dependent insulinotropic peptide?

Answer 17

Also known as gastric inhibitory peptide (GIP)

Question 18

Compare the use of oral versus IV glucose in response to GIP secretion.

Answer 18

An oral glucose load is used more rapidly than the equivalent given by IV due to GIP secretion

Question 19

What is the action of motilin?

Answer 19

Produces migrating motor complexes (MMCs)

Question 20

What is the regulation of motilin?

Answer 20

Increased in fasting state

Question 21

Give an example of a motilin receptor agonists. How are such drugs used?

Answer 21

Motilin receptor agonists (e.g., erythromycin) are used to stimulate intestinal paralysis

Question 22

What are the 3 actions of secretin?

Answer 22

(1) Increase pancreatic HCO3- secretion (2) Decrease gastric acid secretion (3) Increase bile secretion

Question 23

What factors regulate secretin, and how?

Answer 23

Increased by acid, fatty acids in lumen of duodenum

Question 24

What effect does increased HCO3- due to secretin have, and what does this allow?

Answer 24

Increased HCO3- neutralizes gastric acid in duodenum, allowing pancreatic enzymes to function

Question 25

What are the 4 actions of somatostatin?

Answer 25

(1) Decrease gastric acid and pepsinogen secretion (2) Decrease pancreatic and small intestine fluid secretion (3) Decrease gallbladder contraction (3) Decrease insulin and glucagon release

Question 26

What 2 factors regulate somatostatin, and how?

Answer 26

Increased by acid; Decreased by vagal stimulation

Question 27

Give 2 descriptors to explain the kind of hormone that somatostatin is and/or the effects that it has.

Answer 27

(1) Inhibitory hormone (2) Antigrowth hormone effects (inhibits digestion and absorption of substances needed for growth)

Question 28

What is the action of nitric oxide in the GI tract? Where in particular is it noted for acting?

Answer 28

Increase smooth muscle relaxation, including lower esophageal sphincter (LES)

Question 29

In what condition is loss of NO secretion implicated?

Answer 29

Loss of NO secretion is implication in increased LeS tone of achalasia

Question 30

What are the 2 actions of Vasoactive intestinal polypeptide (VIP)?

Answer 30

(1) Increase intestinal water and electrolyte secretion (2) Increase relaxation of intestinal smooth muscle and sphincters

Question 31

What factors increase versus decrease VIP?

Answer 31

Increased by distention and vagal stimulation; Decreased by adrenergic input

Question 32

What is a VIPoma?

Answer 32

VIPoma - non-alpha, non-beta islet cell pancreatic tumor that secretes VIP

Question 33

What are the symptoms of a VIPoma?

Answer 33

copius Watery Diarrhea, Hypokalemia, and Achlorhydria (WDHA syndrome)