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OS GI > Gastric Phys > Flashcards

Gastric Phys Flashcards

1
Q

What are the five gastric secretions?

A 
Acid
Pepsinogens
Mucus
IF
Water
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2
Q

What does the oxyntic gland secrete?

A

HCl

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3
Q

What secretes gastrin?

A

Pyloric mucosa (specific region)

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4
Q

Describe the types of cells in a gastric gland starting most superficial

A

Surface epithelium
Mucous neck cells
Pareital cells (oxyntic)
Peptic (chief) cells

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5
Q

What is the alkaline tide?

A

Venous blood leaving stomach has higher pH than arterial because of bicarbonate after meal

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6
Q

Describe the cellular mechanism of acid secretion

A

CO2 made into HCO3- + H+ by CA. HCO3- diffuses into blood while H is secreted into the blood via a H/K ATPase (K inside).

Cl- is antiported inside when HCO3- leaves, and is then goes through channel into stomach.

Also note the regular Na/K ATPase.

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7
Q

H is secreted __ its electrical gradient and __ its concentration gradient

A

down electrical gradient

against concentration gradient

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8
Q

Cl is secreted __ its electrical gradient and __ its concentration gradient

A

against both

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9
Q

What are some substances that disrupt the stomach cell membranes?

A

ASA

EtOH

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10
Q

How do the concentrations gastric ion secretions change with secretory rate?

A

Cl and H go up with faster rate
K goes up slightly with increase
Na decreases with faster rate

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11
Q

Patients with chronic vomiting have what kind of ion and acid-base disorders?

A

hypokalemia and alkalosis

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12
Q

Describe non-meal state stomach secretions?

A

Low volume production

Isotonic to plasma

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13
Q

Describe acid-secreting state stomach secretions?

A

HCl and potassium
High volume
Parietal cell activity

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14
Q

What are the three secretogogues of acid secretion?

A

Gastrin
Histamine
ACh

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15
Q

How does gastrin stimulate acid secretion?

A

hormone!

CCKB receptor –> Gq/IP3 mechanism that stimulates H/K ATPase

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16
Q

How does ACh stimulate acid secretion?

A

neurocrine!

M3 receptor –> Gq/IP3 mechanism that stimulates H/K ATPase

17
Q

How does histamine stimulate acid secretion?

A

paracrine!

Histamine from ECL cells –> h2 receptor –> Gs/cAMP –> stimulates H/K ATPase

18
Q

Describe the interaction between gastrin levels and acid levels

A

Independent

19
Q

What’s the difference in picking your food vs. not?

A

More acid secretion when you get to pick

20
Q

This phase of acid secretion is entirely mediated by the vagal nerve **

A

Cephalic (30% of secretion) via ACh, even when gastrin is absent

21
Q

Describe the interdigestive output

A

Peaks at night (GERD worst then)

unrelated to plasma gastrin

22
Q

Describe the gastric phase of acid release

A

peaks 20-40 minutes after meal
lasts 3-4 hours
More acid with high protein
Gastrin elevated ~ 1.5h

23
Q

How does the CNS affect acid output based on stimuli?

A

Vagal signals to release ACh and gastrin

24
Q

This substance can inhibit all gastrin release

A

somatostatin

25
Q

What effects on acid secretion does distention have?

A

Stimulates vagus which causes ACH and GRP release

Also stimulates ‘local reflexes’ to release ACH to act on G cells to release gastrin

26
Q

What affect does digested protein have on acid secretion?

A

Stimulates G cells to secrete gastrin

27
Q

What mechanisms of acid secretion are found in all stages?

A

Gastrin - ECL - histamine release

ACh - ECL - histamine release

28
Q

Why does pH rise after a meal?

A

Food buffers

29
Q

Why does the pH begin to fall after the stomach digests a meal?

A

As food is digested the buffer capacity is diminished

30
Q

How is pepsinogen released? 2 ways

A

Vagal stimulation of peptic cell

Acid itself triggers cholinergic stimulation of peptic cells

31
Q

Upon reaching the duodenum, acid causes __ release

A

secretin

32
Q

What is the mechanism of secretin?

A

Acts hormonally to stimulate more pepsinogen release from peptic cells

33
Q

What is the main difference between peptic and duodenal ulcers?

A

Duodenal: ulcers in antrum, fewer secretions
Gastric: ulcers all over stomach, high secretions

OS GI (9 decks)

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