non-endocrine gland endocrinology

Question 1

how does the GIT function as an endocrine organ

Answer 1

• primary function is digestion and absorption of nutrients
• GIT neuro-endocrine system functions to optimize this process
• many gut hormones therefore alter food intake directly and indirectly, the majority acting to reduce food intake and limit meal size

Question 2

what are the main GI hormones

Answer 2

• insulin
• glucagon
• gastrin
• secretin
• cholecystokinin
• gastric inhibiting peptide
• glucagon like peptide
• motilin
• ghrelin

Question 3

where is gastron produced, how is it stimulated and what are the effects

Answer 3

production: G cells in duodenum and stomach
release stimuli: presence of peptides and amino acids in gastric lumen, stomach distension, vagal stimulation and hypercalcaemia
effects: stimulates release of gastric acid from parietal cells and stimualtes release of pepsinogen from chief cells

Question 4

where is secretin produced, when is it released and what are the effects

Answer 4

site: mainly duodenum
release stimuli: H+ in small intestine
major effects: stimulates release of bicarbonate rich pancreatic and biliary fluid

Question 5

where is cholecystokinin produced, what simulates its release and what are its effects

Answer 5

production: mainly duodenum
release stimuli: fatty acids, monoglycerides and amino acids in small intestine
major effects: stimulates secretion of pancreatic enzymes and stimulates contraction and emptying of the gall bladder

Question 6

where is GIP produced, what is the release stimuli and what are the effects

Answer 6

production: proximal small intestine
release stimuli: fat, glucose and amino acids in small intestine
major effects: inhibits gastric secretion and motility, potentiates release of insulin in response to elevated blood glucose concentration, increases insulin sensitivity of adipocytes and stimulates lipoprotein lipase activity in adipocytes

Question 7

discuss the hypothalamic inputs of apetite regulation

Answer 7

• neurons in arcuate nucleus sense blood glucose and hormones and respons with leptin (satiety) or ghrelin (appetite)
• satiety centre responds to high glucose levels and inhibits eating
• appetite centre responds to low glucose levels and stimulates eating

Question 8

discuss the role of CCK on appetite

Answer 8

• synthesised in the small intestine
• acts upon G protein coupled receptors
• released rapidly in response to a meal causing gallbladder contraction, secretion of pancreatic enzymes and bicarbonate, slows gastric emptying, inhibits gastric acid secretion and reduces food intake
• also found in cells of the brain (expansion of the stomach after a meal causes release of cck from these brain cells)

Question 9

describe the role of ghrelin in appetite control

Answer 9

• produced predominantly by the lining of the stomach
• increases beofre meals and decreases after
• stimulates appetite at hypothalamus
• receptors found in brain

Question 10

list renal hormones

Answer 10

• erythropoetin
• renin
• calcitrol

Question 11

list heart hormones

Answer 11

• BNP
• ANP