Tutorials

Question 1

What stomach, duenenal and PNS factors affecting gastrin secretion?

Answer 1

Stomach distention-increases gastrin
Negative feedback of pH in stomach
Duodenum-low pH in duodenum inhbits
High AA in the duodenum means need more digestion-increase
PNS-vagus nerve increases Gastrin secretion

Question 2

What cells produce Gastrin? Where?

Answer 2

G-cells in the stomach pylori, fundus (and a bit in duodenum and pancreas)

Question 3

What is the role of gastrin?

Answer 3

Stimulates parietal cell secretion of HCl and chief cell secretion of pepsinogen

Question 4

How is stomach HCl secreted and produced? In which cells?

Answer 4

HCl are produced in parietal cells
H+ comes from H2O and CO2 =>H2CO3=>HCO3+H
HCO3 is exchanged for a blood Cl- in basolateral (maintain charge equilibrium)-Cl is pumped to canaliculi normally
H+ is pumped to canaliculi/outside in exchange for a K+
AND K+ are pumped back out (to exchange for more)

Question 5

What hormonal factors increase HCl production by parietal cells?
And inhbitit it?

Answer 5

Increases: direct: Histamine H2. Gastrin, ACh, CCK from I- cells
Decrease: Mostly somatostatin

Question 6

What cells produce CCK? And where are they located?

Answer 6

I-cells in the duodenum (1st part)

Question 7

What factors of the stomach, Duodenum, PNS affect CCK production?

Answer 7

Increased by Low stomach pH, high FA and peptides in duodenum =>mixed meal
No hormonal
pancreatic enzymes like Trypsin can inhbit it (negative feedback)

Question 8

What are the roles of CCK?

Answer 8

More gastrin and inhbits stomach motility
contraction of gall bladder to move bile to duodenum
Increase thick enzyme secretion from pancreas acinii

Question 9

What cells produce secretin and where?

Answer 9

S cells-mostly in mucosa of the duodenum and a bit in jujenum

Question 10

What factors in stomach, duodenum and more affect secretin?

Answer 10

Low pH in stomach and duodenum massively increase secretin

Inhibited by H2

Question 11

What are the main roles of secretin?

Answer 11

Inhbit acid secretion in the stomach (both directly and aslo decrease gastrin)
Main role-increase bicarbonate secretion from pancreas
also role in releasing water to buffer the acid chyme

Question 12

What is GIP? where is it produced and by what cells?

Answer 12

Gastric Inhbitory peptide, or glucose-dependent insulinotropic peptide.
Produced by K cells in duodenum and juojenum

Question 13

What stomach, dueodenal, etc factors affect GIP production?

Answer 13

Mixed meal in the duodenum

Question 14

What are the roles of GIP?

Answer 14

Inhbit stomach acid production-as the food is already there

AND increase production of insulin from the pancreas

Question 15

What cells produce somatostatin in the pancreas?

Answer 15

Delta cells

W

Question 16

what are the roles of somatostatin?

Answer 16

Inhbit everything-stomach pepsinogen and acid

Duodenum bicarbonate and absorption (less blood flow), pancreatic insulin, bicarb, glucagon and enzymes

Question 17

What gi factors regulate somatostatin producting?

Answer 17

Low acid pH increase it (dont want to get too low) and vagus nerve decreases it (rest and digest)