GI Endocrinology

Question 1

secretin

Answer 1

after food is digested in stomach with acid it enters duodenum
S cells in duodenum secrete secretin to respond to the acid
secretin signal pancreas to produce more bicarbonate by binding to secretin receptors on basolateral membrane of ductal cells.

this causes on apacial surface of ductal cell CFTR channel move Cl- out of cell (down gradient) and then it is moved back into the cell by SLC26 channel which at the same time move bicarbonate out and move H2O out of the cell due to potential gradient
this bicarbonate neutralise the acidic environment from stomach

cystic fibrosis mutates CFTR which eventually leads to acidic duodenum which denatures enzymes and allows less absorption

Question 2

secretin on gall bladder

Answer 2

also increases bicarbonate production
cholangiocytes line bile duct
when acidic bile moves down bile duct bicarbonate protects cholangiocytes to prevent damage
patients with CF dont get this and can suffer with gall bladder disease

Question 3

cholecystokinin (CCK)

Answer 3

stimulate bile release from gall bladder by stimulating the smooth muscle cells in gall bladder to contract
also affects stomach to slow gastric emptying which gives more time for pancreatic enzymes to reach to duodenum

Question 4

glucagon-like peptide 1 (GLP1)

Answer 4

gut hormone released from L-cells after food intake or vagal stimulation
also stimulates insulin secretion by binding to GLP1 receptors on pancreatic beta cells

GLP1 neurons present in brain respond to certain visceral stimuli and release GLP1 to areas of CNS which are responsible for hunger and happiness

an infusion of GLP1 can decrease hunger and increase satiety without actually eating and can also help patients reduce obesity

Question 5

ghrelin

Answer 5

the hunger hormone
relased by X/A cells, peak before mealtimes
can increase body weight and hunger/food intake by sending signals to feeding centre in hypothalamus
this area contains POMC and NYP neurones. POMC signal paraventricular nucleus to induce satiety. NYP inhibit POMC to induce hunger and they are stimulated by ghrelin

Question 6

verticle sleeve gastrectomy

Answer 6

surgical procedure to reduce obesity by removing part of stomach including fundus of stomach which removes X/A ghrelin cells which this with stomach volume loss is what causes these patients to lose weight