Gastrointestinal regulatory substances

Question 1

Source of gastrin

Answer 1

G cells (antrum of stomach, duodenum)

Question 2

Action of gastrin

Answer 2

• ↑ gastric H+ secretion
• ↑ growth of gastric mucosa
• ↑ gastric motility

Question 3

Regulation of gastrin

Answer 3

• ↑ by stomach distention/ alkalinization, amino acids, peptides, vagal stimulation via gastrin releasing peptide (GRP)
• ↓ by pH

Question 4

Source of somatostatin

Answer 4

D cells (pancreatic islets, GI mucosa)

Question 5

Action of somatostatin

Answer 5

• ↓ gastric and pepsinogen secretion
• ↓ pancreatic and small intestine fluid secretion
• ↓ gallbladder contraction
• ↓ insulin and glucagon release

Question 6

Regulation of somatostatin

Answer 6

• ↑ by acid

- ↓ by vagal stimulation

Question 7

Source of cholecystokinin

Answer 7

I cell (duodenum, jejunum)

Question 8

Action of cholecystokinin

Answer 8

• ↑ pancreatic secretion
• ↑ gallbladder contraction
• ↓ gastric emptying
• ↑ sphincter of Oddi relaxation

Question 9

Regulation of cholecystokinin

Answer 9

↑ by fatty acids and amino acids

Question 10

Source of secretin

Answer 10

S cells (duodenum)

Question 11

Action of secretin

Answer 11

• ↑ pancreatic HCO3- secretion
• ↓ gastric acid secretion
• ↑ bile secretion

Question 12

Regulation of secretin

Answer 12

↑ by acid, fatty acids in lumen of duodenum

Question 13

Sources of glucose-dependent insulinotropic peptide

Answer 13

K cells (duodenum, jejunum)

Question 14

Action of glucose-dependent insulinotropic peptide

Answer 14

• Exocrine: ↓ gastric H+ secretion

- Endocrine: ↑ insulin release

Question 15

Regulation of glucose-dependent insulinotropic peptide

Answer 15

↑ by fatty acids, amino acids and oral glucose

Question 16

Source of motilin

Answer 16

Small intestine

Question 17

Action of motilin

Answer 17

Produces migrating motor complexes (MMCs)

Question 18

Regulation of motilin

Answer 18

↑ in fasting state

Question 19

Sources of vasoactive intestinal peptide

Answer 19

Parasympathetic ganglia in sphincters, gallbladder, and small intestine

Question 20

Action of vasoactive intestinal peptide

Answer 20

• ↑ intestinal water and electrolyte secretion

- ↑ relaxation of intestinal smooth muscle and sphincters

Question 21

Regulation of vasoactive intestinal peptide

Answer 21

• ↑ by distention and vagal stimulation

- ↓ by adrenergic input

Question 22

Action of nitric oxide

Answer 22

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

Question 23

Source of ghrelin

Answer 23

Stomach

Question 24

Action of ghrelin

Answer 24

↑ appetite

Question 25

Regulation of ghrelin

Answer 25

• ↑ in fasting state

- ↓ by food

Question 26

Source of intrinsic factor

Answer 26

Parietal cells (stomach)

Question 27

Action of intrinsic factor

Answer 27

Vitamin B12 binding protein required for B12 uptake in the terminal ileum

Question 28

Source of gastric acid

Answer 28

Parietal cells (stomach)

Question 29

Action of gastric acid

Answer 29

↓ stomach pH

Question 30

Regulation of gastric acid

Answer 30

• ↑ by histamine, ACh, gastrin

- ↓ by somatostatin, glucose-dependent insulionotropic peptide (GIP), prostaglandin, secretin

Question 31

Source of pepsin

Answer 31

Chief cells (stomach)

Question 32

Action of pepsin

Answer 32

Protein digestion

Question 33

Regulation of pepsin

Answer 33

↑ by vagal stimulation and local acid

Question 34

Source of bicarbonate

Answer 34

• Mucosal cells (stomach, duodenum, salivary glands, pancreas)
• Brunner glands (duodenum)

Question 35

Action of bicarbonate

Answer 35

Neutralizes acid

Question 36

Regulation of bicarbonate

Answer 36

↑ by pancreatic and biliary secretion with secretin