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GASTROINTESTINAL PHYSIOLOGY > Gastric Secretion > Flashcards

Gastric Secretion Flashcards

1
Q

What is function of the fundus of the stomach?

A

Storage

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2
Q

What is the function of the body of the stomach?

A

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

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3
Q

What is the function of the antrum of the stomach?

A

Mixing and grinding

Production of gastrin

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4
Q

How is the antrum equipped for grinding of food?

A

Thicker/more powerful muscularis

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5
Q

How is gastrin produced?

A

G-cells

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6
Q

What is the function of mucus in the stomach?

A

Prevent autodigestion of the stomach by HCl

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7
Q

What is the cellular composition of gastric glands?

A

Mucus neck cells
Chief Cells
Parietal cells

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8
Q

What do neck cells produce?

A

Precursors to surface mucous cells

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9
Q

Where is pepsinogen produced?

A

Chief cells

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10
Q

What do parietal cells produce?

A

HCl

Intrinsic factor

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11
Q

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

A

CO2 pulled from blood

Combined with water and Carbionic Anhydrase to form H2CO3

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12
Q

What is the fate of H2CO3?

A

Very unstable
Dissociates to:
HCO3
H

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13
Q

What is the fate of dissociated protons?

A

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

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14
Q

How do Proton pumps work?

A

One H exchanged for 1 K using H-K ATPase

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15
Q

What is the fate of dissociated carbonate?

A

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

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16
Q

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

A

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

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17
Q

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

A

Metabolic waste

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18
Q

How does Gastrin effect protein pumps?

A

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

19
Q

How does acetylcholine effect protein pumps?

A

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

20
Q

How does Histamine effect protein pumps?

A

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

21
Q

How do prostaglandins effect protein pumps?

A

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

22
Q

Which gastric acid secretion mechanism is neurocrine?

A

Vagus/local reflexes

23
Q

Which gastric acid secretion mechanism is endocrine?

A

gastrin

24
Q

Which gastric acid secretion mechanism is paracrine?

A

Histamine

25
Q

What is the cephalic phase of Gastric acid secretion?

A

Seeing/smelling/tasting food causing vagal stimulation

26
Q

How does vagus stimulation effect gastric acid secretion?

A

Increased ACh

Stimulation of G-cells: increase of gastrin

27
Q

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

A

Triggers histamine release

28
Q

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

A

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

29
Q

How do peptides in the lumen stimulate gastric acid production?

A

Stimulation of G-cells to release gastrin

30
Q

How do gastrin and ACh stimulate gastric acid production?

A

Stimulation of ECL cells which release Histamine

31
Q

How does stopping eating effect gastric acid secretion?

A

Inhibition due to reduced vagal activity

32
Q

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

A

Inhibitory - Gastrin secretion is reduced

33
Q

Acid in the duodenum triggers what?

A

Enterogastric reflex

Secretin release

34
Q

The Enterogastric reflex and Secretin release trigger what?

A

Decreased Gastrin secretion

Decreased gastrin effect on parietal cells

35
Q

Fat or CHO in duodenum trigger what?

A

GIP release

36
Q

GIP triggers what?

A

Reduced gastrin secretion

Reduced parietal HCl secretion

37
Q

What are enterogastrones?

A

Hormones released from gland cells in duodenal mucosa
Secretin
CCK
GIP

38
Q

When are enterogastrones released?

A

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

39
Q

What is the role of enterogastrones?

A

Prevent further acid build up in the duodenum

40
Q

How do enterogastrones slow acid build up?

A

Inhibit gastric abit

Contract pyloric sphincter (slow emptying)

41
Q

Pepsinogen is converted into pepsin when?

A

pH < 3

Presense of other pepsin

42
Q

How is pepsin neutralised?

A

Neutral pH

43
Q

What is the role of pepsin?

A

Cleaves peptide bonds (endopeptidase)

GASTROINTESTINAL PHYSIOLOGY (10 decks)

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