Gastric Secretion

Question 1

What is function of the fundus of the stomach?

Answer 1

Storage

Question 2

What is the function of the body of the stomach?

Answer 2

Storage
Production of:
Mucus, HCl, Pepsinogen, Intrinsic Factor

Question 3

What is the function of the antrum of the stomach?

Answer 3

Mixing and grinding

Production of gastrin

Question 4

How is the antrum equipped for grinding of food?

Answer 4

Thicker/more powerful muscularis

Question 5

How is gastrin produced?

Answer 5

G-cells

Question 6

What is the function of mucus in the stomach?

Answer 6

Prevent autodigestion of the stomach by HCl

Question 7

What is the cellular composition of gastric glands?

Answer 7

Mucus neck cells
Chief Cells
Parietal cells

Question 8

What do neck cells produce?

Answer 8

Precursors to surface mucous cells

Question 9

Where is pepsinogen produced?

Answer 9

Chief cells

Question 10

What do parietal cells produce?

Answer 10

HCl

Intrinsic factor

Question 11

How is H2CO3 produced in the parietal cells of the stomach?

Answer 11

CO2 pulled from blood

Combined with water and Carbionic Anhydrase to form H2CO3

Question 12

What is the fate of H2CO3?

Answer 12

Very unstable
Dissociates to:
HCO3
H

Question 13

What is the fate of dissociated protons?

Answer 13

Active loading from the parietal cell into the lumen via proton pumps

Question 14

How do Proton pumps work?

Answer 14

One H exchanged for 1 K using H-K ATPase

Question 15

What is the fate of dissociated carbonate?

Answer 15

Pumped out of the parietal cells into the blood in exchange for Cl

Question 16

What is the effect of the Cl entering the cell from the blood?

Answer 16

Cl passively flows from the parietal cell into the lumen, creating an osmotic gradient which water follows into the lumen

Question 17

What is the source of CO2 for the production of protons?

Answer 17

Metabolic waste

Question 18

How does Gastrin effect protein pumps?

Answer 18

Gastrin -> Ca release -> Stimulation of protein kinase -> increased protein pump activity

Question 19

How does acetylcholine effect protein pumps?

Answer 19

Gastrin -> Ca release -> Stimulation of protein kinase -> increased protein pump activity

Question 20

How does Histamine effect protein pumps?

Answer 20

Gs coupled reactor converts ATP –> cAMP which triggers protein kinase and increases PP activity

Question 21

How do prostaglandins effect protein pumps?

Answer 21

Activate G-inhibitory proteins and stop the conversion of ATP –> cAMP, reducing protein kinase activity .’. reducing PP activity

Question 22

Which gastric acid secretion mechanism is neurocrine?

Answer 22

Vagus/local reflexes

Question 23

Which gastric acid secretion mechanism is endocrine?

Answer 23

gastrin

Question 24

Which gastric acid secretion mechanism is paracrine?

Answer 24

Histamine

Question 25

What is the cephalic phase of Gastric acid secretion?

Answer 25

Seeing/smelling/tasting food causing vagal stimulation

Question 26

How does vagus stimulation effect gastric acid secretion?

Answer 26

Increased ACh | Stimulation of G-cells: increase of gastrin

Question 27

What is the effect of Gastrin and ACh on ECL cells?

Answer 27

Triggers histamine release

Question 28

How does the distension of the stomach stimulate gastric acid production?

Answer 28

Distension of the stomach stimulates Vagal/Enteric reflexes - triggering ACh release

Question 29

How do peptides in the lumen stimulate gastric acid production?

Answer 29

Stimulation of G-cells to release gastrin

Question 30

How do gastrin and ACh stimulate gastric acid production?

Answer 30

Stimulation of ECL cells which release Histamine

Question 31

How does stopping eating effect gastric acid secretion?

Answer 31

Inhibition due to reduced vagal activity

Question 32

What is the effect of pH falling on gastric acid secretion?

Answer 32

Inhibitory - Gastrin secretion is reduced

Question 33

Acid in the duodenum triggers what?

Answer 33

Enterogastric reflex | Secretin release

Question 34

The Enterogastric reflex and Secretin release trigger what?

Answer 34

Decreased Gastrin secretion | Decreased gastrin effect on parietal cells

Question 35

Fat or CHO in duodenum trigger what?

Answer 35

GIP release

Question 36

GIP triggers what?

Answer 36

Reduced gastrin secretion | Reduced parietal HCl secretion

Question 37

What are enterogastrones?

Answer 37

Hormones released from gland cells in duodenal mucosa Secretin CCK GIP

Question 38

When are enterogastrones released?

Answer 38

Response to acid, hypertonic sltn, FAs or CHOs in the duodenum

Question 39

What is the role of enterogastrones?

Answer 39

Prevent further acid build up in the duodenum

Question 40

How do enterogastrones slow acid build up?

Answer 40

Inhibit gastric abit | Contract pyloric sphincter (slow emptying)

Question 41

Pepsinogen is converted into pepsin when?

Answer 41

pH < 3 | Presense of other pepsin

Question 42

How is pepsin neutralised?

Answer 42

Neutral pH

Question 43

What is the role of pepsin?

Answer 43

Cleaves peptide bonds (endopeptidase)