Gastric Phys

Question 1

What are the five gastric secretions?

Answer 1

Acid
Pepsinogens
Mucus
IF
Water

Question 2

What does the oxyntic gland secrete?

Answer 2

HCl

Question 3

What secretes gastrin?

Answer 3

Pyloric mucosa (specific region)

Question 4

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

Answer 4

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

Question 5

What is the alkaline tide?

Answer 5

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

Question 6

Describe the cellular mechanism of acid secretion

Answer 6

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.

Question 7

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

Answer 7

down electrical gradient

against concentration gradient

Question 8

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

Answer 8

against both

Question 9

What are some substances that disrupt the stomach cell membranes?

Answer 9

ASA

EtOH

Question 10

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

Answer 10

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

Question 11

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

Answer 11

hypokalemia and alkalosis

Question 12

Describe non-meal state stomach secretions?

Answer 12

Low volume production

Isotonic to plasma

Question 13

Describe acid-secreting state stomach secretions?

Answer 13

HCl and potassium
High volume
Parietal cell activity

Question 14

What are the three secretogogues of acid secretion?

Answer 14

Gastrin
Histamine
ACh

Question 15

How does gastrin stimulate acid secretion?

Answer 15

hormone!

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

Question 16

How does ACh stimulate acid secretion?

Answer 16

neurocrine!

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

Question 17

How does histamine stimulate acid secretion?

Answer 17

paracrine!

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

Question 18

Describe the interaction between gastrin levels and acid levels

Answer 18

Independent

Question 19

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

Answer 19

More acid secretion when you get to pick

Question 20

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

Answer 20

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

Question 21

Describe the interdigestive output

Answer 21

Peaks at night (GERD worst then)

unrelated to plasma gastrin

Question 22

Describe the gastric phase of acid release

Answer 22

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

Question 23

How does the CNS affect acid output based on stimuli?

Answer 23

Vagal signals to release ACh and gastrin

Question 24

This substance can inhibit all gastrin release

Answer 24

somatostatin

Question 25

What effects on acid secretion does distention have?

Answer 25

Stimulates vagus which causes ACH and GRP release Also stimulates 'local reflexes' to release ACH to act on G cells to release gastrin

Question 26

What affect does digested protein have on acid secretion?

Answer 26

Stimulates G cells to secrete gastrin

Question 27

What mechanisms of acid secretion are found in all stages?

Answer 27

Gastrin - ECL - histamine release | ACh - ECL - histamine release

Question 28

Why does pH rise after a meal?

Answer 28

Food buffers

Question 29

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

Answer 29

As food is digested the buffer capacity is diminished

Question 30

How is pepsinogen released? 2 ways

Answer 30

Vagal stimulation of peptic cell | Acid itself triggers cholinergic stimulation of peptic cells

Question 31

Upon reaching the duodenum, acid causes __ release

Answer 31

secretin

Question 32

What is the mechanism of secretin?

Answer 32

Acts hormonally to stimulate more pepsinogen release from peptic cells

Question 33

What is the main difference between peptic and duodenal ulcers?

Answer 33

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