Peptidergic regulation of the GIT Flashcards
Define endocrine, paracrine and neurocrine
endocrine - cells release hormone into the blood for far target
paracrine - messenger into ecf for neighbouring effect - immediate
neuroncrine - sensory - inter - motor - neurotransmitter released for acute effect
what is the source, stimulus, pathway and target of gastrin in the stomach
Released from g cells
stimulated by neural input, aa or peptides in the stomach
endocrine pathway
targets ecl and parietal cells
what is the source, stimulus, pathway and target of CCK
released from I cells in the duodenum
stimulated by ffa and some aa
paracrine and endocrine
targets vagal afferents and pancreatic acing cells
what is the source, stimulus, pathway and target of secretin
S cells in the duodenum
stimulated bu acid in then small intestine
endocrine and paracrine
vagal afferent and pancreatic duct cells
what is the source, stimulus, pathway and target of motilin
Intestine
neural input or fasting
paracine
upper GI motility
what is the source, stimulus, pathway and target of Gastric inhibitory peptide (GIP)
k cells in the intestine
fatty acids, glucose and aa in the small intestine
endocrine
B cells in the pancreas
what is the source, stimulus, pathway and target of GLP-1
L cells in the intestine
carbs and ffa
endocrine and paracrine
endocrine pancreas
what is the source, pathway and target of vasoactive intestinal peptide throughout the intestine
nerve terminals
neurocine
secretory cells
what are peptides released from and from where
APUD
amine precursor uptake decarboxylation cells on epithelial cells of the git
what do mucus neck cells secrete
mucus and bicarbonate
what do parietal cells secrete
HCL and intrinsic factor
what do ECL cells secrete
histamine
what do chief cells secrete
pepsinogen
gastric lipase
what do d cells secrete
somatostatin
what do g cells secrete
gastrin
where are g cells located
in the bottom of crypts in the antrum and duodenum
what are the two effects of gastrin
stimulate both ecl and parietal cells
increases mucosal growth
what is the cephalic reflex and what kind of mechanism is it
feedforward mechanism
sight or small of food induces vagal input to g cells to simulate gastrin release
what happens to gastrin release when food reaches the stomach and why
food hits the stomach and peptides and aa present stimulate more gastrin release
what does histamine do
stimulates parietal cells to release more hcl
what does a high acid conc in the stomach do to chief cells
triggers chief cells to release pepsinogen which gets metabolised to pepsin which hydrolyses proteins to aa which further releases gastrin
describe the negative feedback when acid conc is high in the stomach
low ph stimulates d cells to release somatostatin which inhibits g cells, ecl cells and parietal cells
how is gastrin inhibited
d cells
reduced cephalic reflex
reduced neural input
what is zollinger ellison syndrome
tumour of the pancreas which stimulates g cells in the stomach to secrete more gastrin
what is a gastrinoma
tumour of g cells in the stomach hyper secretion of gastrin
how could you test for ellison zollinger syndrome
give them secretin and if theres no change in acid levels then there is a gastronoma or tumour of the pancreas causing stimulation of g cells
what are the symptoms of elision zolinger syndrome
peptic ulcer causing bleeding
diarrhoea
heart burn
low potassium and calcium levels
how would you treat EZS
remove the tumour via surgery
use proton pump inhibitors
what does secretin do in EZS
increase bicarbonate concentration via increases in bile fluids and pancreatic fluids to try and neutralise acid build up
what do duodenal I cells do
secrete cck increasing bile production and decreases gastric secretions and motility
also increases number of pancreatic cells
what does vasoactive inhibitory peptide do (VIP)
released from nerve terminals in the gut
causes dilation of smooth muscle
increase in salivary gland blood flow
increase in intestinal fluid
what is verner morrison syndrome and what are the symptoms
excessive secretions
low chloride and potassium levels
excessive tropic effect of the pancreatic cells
what is the treatment of verner morrison syndrome
removal of the tumour from the tail of the pancreas
rebalance the electrolytes and fluids
octreotide inhibitor
