Gastric Secretion

Question 1

role of chief cell

Answer 1

secrete pepsinogens

Question 2

what is a zymogen

Answer 2

an inactive precursor to an active enzyme or substance e.g. pepsinogen –> pepsin

Question 3

cells that secret HCl

Answer 3

parietal cells

Question 4

secretions of parietal cells

Answer 4

HCl and intrinsic factor

Question 5

what is intrinsic factor important for

Answer 5

transport of vit B12

Question 6

mucus is secreted by what cells type in the gastric gland

Answer 6

surface and neck mucous cells

Question 7

production of stomach acid requires entry of what two substances into the cell

Answer 7

Cl and CO2

Question 8

in stomach acid production what is released back into the blood

Answer 8

bicarbonate (HCO3)

Question 9

pH of stomach acid

Answer 9

<2

Question 10

what moves across the leaky tight junctions of stomach epithelium as stomach acid is made

Answer 10

water

Question 11

3 substances that stimulate gastric acid secretion

Answer 11

gastrin, histamine and acetylcholine

Question 12

where does gastric acid production occur

Answer 12

in parietal cells

Question 13

how do gastrin, histamine and ACh stimulate gastric acid production

Answer 13

by stimulating the K/H primary active pump

Question 14

mechanism of histamine on acid secretion

Answer 14

1. unique receptor when in gut stimulates a G protein coupled to AC
2. AC makes ATP to cyclic AMP
3. cAMP acts on proteins kinases to stimulate K/H pump

Question 15

how do prostaglandins inhibit secretion

Answer 15

turns off AC thus stopping cAMP being made

Question 16

neurocrine control gastric secretion

Answer 16

ACh

Question 17

endocrine control of gastric secretion

Answer 17

gastrin

Question 18

paracrine control of gastric secretion

Answer 18

histamine

Question 19

what cells secrete histamine

Answer 19

ECL cells

Question 20

what substances stimulate ECL cells to release histamine

Answer 20

gastrin and ACh

Question 21

what stimulates G cells to release gastrin

Answer 21

1. peptides in stomach lumen

2. vagus nerve

Question 22

what initial input triggers the vagal and enteric reflexes for gastric secretion

Answer 22

food in stomach causing distension

Question 23

presence of acid and fat has what effect on gastrin and HCl secretion

Answer 23

inhibition

Question 24

reflex that communicates acid in duodenum to stop gastrin and hence gastric secretion

Answer 24

enterogastric (splanchnic reflex)

Question 25

what is an enterogastrone

Answer 25

a hormone released from gland cells in the duodenum

Question 26

what are the 3 main enterogastrones

Answer 26

secretin, cholecystokinin (CCK) and GIP

Question 27

enterogastrones are released in response to

Answer 27

acid, fatty acids, monoglyceridres and hypertonic solutions

Question 28

enterogastrones effect on acid secretion and gastric emptying

Answer 28

inhibit acid secretion

reduce gastric emptying

Question 29

inactive precursor of pepsin

Answer 29

pepsinogen

Question 30

what pH changes pepsinogen to pepsin

Answer 30

pH <3

Question 31

what pH inactivates pepsins

Answer 31

neutral (i.e. pH 7)

Question 32

how does mucus protect against damage by acid and pepsin

Answer 32

pepsin will be inactivated by neutral pH (high bicarbonate)

physical barrier to acid

Question 33

which cells produce intrinsic factor

Answer 33

parietal cells

Question 34

lack of intrinsic factor and hence B12 absorption cause what condition

Answer 34

pernicious anaemia