Gastric Secretion

Question 1

what do mucous neck cells secrete?

Answer 1

mucus

Question 2

what do chief cells secrete?

Answer 2

pepsinogen

Question 3

what do parietal cells secrete?

Answer 3

> HCL

> intrinsic factor

Question 4

what is the cellular composition of gastric glands?

Answer 4

> mucous neck cells
chief cells
parietal cells

Question 5

what are the three mechanisms which control gastric acid secretion?

Answer 5

> neurocrine (vagus reflex)
endocrine (gastrin)
paracrine (histamine)

Question 6

in the celiac phase for stimulating gastric acid secretion what 3 things act on parietal cells?

Answer 6

> acetylcholine from vagus nerve
gastrin from g-cells
histamine from ECL cells

Question 7

what activates the vagus nerve in the celiac phase of stimulating gastric acid secretion?

Answer 7

sight, smell and taste of food

Question 8

what stimulates the ECL cells to produce histamine I the celiac phase of gastric acid secretion?

Answer 8

gastrin and acetylcholine

Question 9

in the gastric phase what activates the vagal/enteric reflexes?

Answer 9

distension of the stomach (arrival of food)

Question 10

what activates G-cells to produce gastrin in the gastric phase?

Answer 10

peptides in the lumen

Question 11

what activates ECL cells to produce histamine in the gastric phase?

Answer 11

gastrin and acetylcholine

Question 12

in the gastric phase what cells does ACh, gastrin and histamine work on?

Answer 12

parietal cells

Question 13

what inhibits gastric secretion in the cephalic phase?

Answer 13

cessation of eating which causes a decrease in vagal activity

Question 14

what mechanisms inhibit gastric secretion in the gastric phase?

Answer 14

a decrease in pH creates a decrease in gastrin production

Question 15

in the intestinal phase what is the effect of acid in the duodenum?

Answer 15

enterogastric (splanchnic reflex) and secretin release

= decrease in gastrin secretion and gastrin stimulation of parietal cells

Question 16

what is released in response to fat in the duodenum?

Answer 16

GIP

Question 17

what is the effect of gastrin release?

Answer 17

gastrin secretion and parietal HCl secretion

Question 18

name some enterogastrones

Answer 18

> secretin, cholecystokinin, GIP

Question 19

what releases enterogastrones?

Answer 19

gland cells in the duodenal mucosa

Question 20

what are enterogastrones released in response to?

Answer 20

> acid
> hypertonic solutions
> fatty acids
> monoglycerides
in the duodenum

Question 21

what to enterogastrones work to prevent?

Answer 21

further acid build up in the duodenum

Question 22

what two strategies do enterogastrones use to prevent acid build up in the duodenum?

Answer 22

> inhibition of gastric secretion

> reduced gastric emptying (inhibition of motility/contraction of pyloric sphincter)

Question 23

what secretes pepsinogen?

Answer 23

chief cells

Question 24

what is zymogen?

Answer 24

inactive precursor to pepsinogen that prevents cellular digestion

Question 25

what inactivates pepsinogen?

Answer 25

neutral pH

Question 26

what produces gastric mucus?

Answer 26

surface epithelial cells and mucus neck cells

Question 27

what does mucus protect the surface from?

Answer 27

> mechanical injury > gastric acid corrosion > pepsin digestion

Question 28

what is the only non-compensated function of the stomach?

Answer 28

intrinsic factor secretion

Question 29

what is intrinsic factor required for?

Answer 29

vit. b12 absorption

Question 30

what can a defect in vit. 12 absorption lead to?

Answer 30

pernicious anaemia - failure of erythrocytes maturation

Question 31

describe how carbonic acid is created in gastric glands

Answer 31

co2 enters the cell and combines with h2o creating carbonic acid.

Question 32

what channel is H+ ion pumped out through?

Answer 32

potassium channel into the lumen

Question 33

what membrane is carbonate pumped out of?

Answer 33

the basolateral membrane

Question 34

how does water enter the lumen of the stomach?

Answer 34

through the para-cellular pathway

Question 35

describe what happens in the cell when gastrin binds to it's g protein coupled receptor

Answer 35

the activation of the receptor causes a rise in calcium that activates protein kinase that causes an increase in H ions being pumped by the proton pump into the stomach lumen

Question 36

describe the histamine receptor used in gastric secretion control

Answer 36

it is a unique g protein coupled receptor: H2

Question 37

what do prostaglandins inhibit when they bind to receptors of the stomach?

Answer 37

cAMP

Question 38

what is the effect of prostaglandin binding to their receptors in the activity of the proton pump?

Answer 38

it causes decreased activity of the proton pump