4. GIT Function 2

Question 1

What factors inhibit acid secretion?

Answer 1

Enterogastric reflex

Presence of acid, fat and protein in duodenum

Question 2

What is the enterogastric refex?

Answer 2

Distension of the duodenum results in reduced gastric motility and stomach emptying

Question 3

What does presence of fatty acids and amino acids in the duodenum cause?

Answer 3

Secretion of cholecystokinin

Question 4

What does presence of acid in the duodenum cause?

Answer 4

Secretion of secretin

Question 5

What drugs can inhibit acid secretion?

Answer 5

Histamine H2 antagonists

Proton pump inhibitors

Question 6

What usually happens when histamine acts of a H2 receptor?

Answer 6

Stimulates adenylate cyclase
Increases cAMP production
Increases H+ secretion

Question 7

What is the effect of histamine H2 antagonists?

Answer 7

Reduces histamine and gastrin-stimulated acid secretion

Question 8

Name a H2 antagonist?

Answer 8

Cimetidine

Question 9

What is the action of proton pump inhibitors?

Answer 9

Irreversibly inhibits H+/K+ ATPase

Inhibits basal and stimulated acid secretion

Question 10

Name a proton pump inhibitor

Answer 10

Omeprazole

Question 11

What is CCK stimulated by?

Answer 11

Increased levels of fatty acids and amino acids in the duodenum
Activation of sensory afferents and effector nerves with the neurotransmitter CCK releasing peptide

Question 12

What are the functions of CCK?

Answer 12

Inhibits gastric motility and acid secretion by activating CCKa receptors on D cells of pancreas and stomach to release somatostatin
Trophic to endocrine pancreas to increase secretion of pancreatic enzymes
Causes contraction of the gall bladder and relaxation of the sphincter of Oddi

Question 13

What is secretin release stimulated by?

Answer 13

Presence of acid in duodenum

Activation of sensory afferents and effector nerves with neurotransmitter Secretin Releasing Peptide

Question 14

What are the functions of secretin?

Answer 14

Inhibits gastric motility and acid secretion
Stimulates pancreatic duct cells to produce HCO3-
Stimulates liver to secrete bile
Inhibits gastric emptying

Question 15

Which pancreatic cells produce enzymes?

Answer 15

Acinar cells

Question 16

Which pancratic cells produce HCO3- and water?

Answer 16

Ductal epithelial cells

Question 17

What is the neural control of pancreatic secretions?

Answer 17

Vagus, enteric reflexes, ACh

Question 18

What is the hormonal control of pancreatic secretion?

Answer 18

Gastrin, CCK, secretin

Question 19

What are the 3 phases of pancreatic secretion?

Answer 19

Cephalic/reflex phase
Gastric phase
Intestinal phase

Question 20

What is the control of the cephalic phase?

Answer 20

ACh from Vagus

Question 21

What happens during the cephalic and gastric phases?

Answer 21

Release of a low volume of enzymes from acinar cells

Low volume aqueous NaHCO3- from ductal cells

Question 22

What is the control of the gastric phase?

Answer 22

Short reflexes stimulated by stretch and chemoreceptors

Gastrin (presence of peptides and AAs in chyme)

Question 23

What is the control of the intestinal phase?

Answer 23

Enterogastric reflexes
CCK (presence of FAs and AAs)
Secretin (acid)

Question 24

What happens during the intestinal phase?

Answer 24

Increased enzyme production in acinar cells
Secretion of HCO3- and water from epithelial duct cells
Increased cAMP (active anionic transport)
Acid is neutralised

Question 25

Describe the steps in bile secretion

Answer 25

1. Vagus nerve stimulates bile production by the liver 2. FAs and AAs in chyme stimulate CCK Acid stimulates secretin 3. CCK causes contraction of the gall bladder 4. Secretin causes secretion of bile from the liver

Question 26

Where are Brunner's glands?

Answer 26

Submucosal layer of the duodenum

Question 27

What is the function of Brunner's glands?

Answer 27

Secrete alkaline mucous to protect from acid

Question 28

What increases mucous secretion by Brunner's glands?

Answer 28

Enteric reflex (distension) Vagal stimulation CCK and secretin

Question 29

Which hormones play a role in GI motility?

Answer 29

Motilin Serotonin (5-HT) Gastric Inhibitory Polypeptide Somatostatin

Question 30

What is motilin?

Answer 30

Peptide from the mucosa of the upper GI

Question 31

What is the role of motilin?

Answer 31

Causes contractions of the stomach when fasting to signal hunger Helps clear intestine of foreign bodies

Question 32

What is the migrating motor complex?

Answer 32

Waves of contraction of the small intestine every 1.5-2 hours in the absence of food

Question 33

What is 5-HT released from?

Answer 33

Enterochromaffin cells

Question 34

What does overstimulation of 5-HT3 receptors cause?

Answer 34

Nausea and vomiting

Question 35

Name a drug that blocks 5-HT3 receptors on sensory fibres

Answer 35

Ondansetron

Question 36

Where is GIP released from?

Answer 36

Duodenal mucosa

Question 37

What is GIP released in response to?

Answer 37

Food in intestine

Question 38

What is the function of GIP?

Answer 38

Inhibits acid secretion | Stimulates insulin production by pancreas