Physiology: pancreas

What are the exocrine cells of the pancreas?

acinar cells and ductal cells

what are the endocrine cells of the pancreas and what are they responsible for?

islet of langerhans; glucose metabolism

endocrine: also does hormone production

the exocrine functional unit is made up of the acinus and the duct, what are their main basic functions?

acinus: produces the pancreatic digestive enzymes

duct: collects the digestive enzymes (pancreatic “juices”) that eventually go into the duodenum

what two pathways are regulators in exocrine function during the intestinal phase?

the endocrine and neurocrine pathways secrete hormones that regulate exocrine (digestive) functions of the pancreas

what two hormones/substances are responsible for bicarb secretion in the duct?

secretin and acetylcholine

_____ cells secrete enzymes (proteases, amylases, lipases, and nucleases)

acinar cells

____ has the potential to damage the pancreas, so it is secreted in inactive forms to prevent auto-digestion of the pancreas

proteases

digestive enzymes are packaged into secretory vesicles called ___

zymogen granules

duct cells are responsible for ____

secretion of bicarb

GRP, CCK, and acetylcholine increase ____ which works to synergistically increase the amount of pancreatic digestive enzymes that are secreted

increase Ca2+ (other hormones increase cAMP, and when cAMP and Ca2+ are both increased, the amount of digestive enzymes gets bigger because of synergy)

Secretin and VIP increase ___ which works to synergistically increase the amount of pancreatic digestive enzymes that are secreted

increase cAMP (other hormones increase Ca2+, and when cAMP and Ca2+ are both increased, the amount of digestive enzymes gets bigger because of synergy)

What enzyme from the pancreas breaks down starch

amylase

starch → maltose

What enzyme from the pancreas breaks down fats

lipase

fats → fatty acids and glycerol

What enzyme from the pancreas breaks down polypeptides (proteins)

trypsin

proteins → amino acids

enterokinase that are at the border between the pancreas and the duodenum convert ___ to ____

trypsinogen to trypsin, then trypsin converts all the other zymogens to their active forms

this seems to be a protective measure that they are inactive until they are going into the duodenum

give a brief overview of protein breakdown (metabolism)

proteins first get hydrolyzed into either peptides (chains of amino acids) or amino acids, and eventually they get broken down into the individual amino acids that are then secreted into the blood stream

duct cells respond to _____

secretin and acetylcholine (to make bicarb)

acinar cells respond to ___

CCK, secretin, VIP, GRP, and acetylcholine (to make digestive enzymes)

which ones are hormonal and which ones are neuronal? (endocrine vs neurocrine)

secretin, acetylcholine, CCK, VIP, GRP

secretin and CCK: hormonal

acetylcholine, VIP, and GRP: neural

the ductule cells do what?

secrete water and bicarb

explain secretin, CFTR, and bicarb secretion

secretin binds to the secretin receptor which increases cAMP, then the cAMP can activate the CFTR to stimulate the secretion of bicarb and sodium

CFTR: takes Cl and makes an electrical gradient to push out more bicarb

Explain cystic fibrosis and how aqueous secretions are affected? what is the result?

cystic fibrosis causes no aqueous secretions but instead you get mucous plugs in the airways and pancreas→ in the pancreas this can lead to malabsorption

CCK and secretin are ___ in the stomach and ____ in the pancreas, explain why this makes sense

they are inhibitory in the stomach and stimulatory in the pancreas

this is because in the intestinal phase (where CCK and secretin come into play) the food has moved from the stomach to the duodenum, so acid production doesn’t need to occur in the stomach anymore, but it does in the intestine

What are the mediators of the cephalic, gastric, and intestinal phases?

cephalic: vagus nerve

gastric: vagus nerve

intestinal: CCK, secretin, ad vagus nerve

briefly describe the cephalic, gastric, and intestinal phases

cephalic: sight and smell, thinking about food, or chewing

gastric: food enters the stomach

intestinal: food and acid enter the duodenum

explain CCK’s role in pancreatic function

fatty acids and amino acids enter the intestines → small intestine releases CCK → increased plasma CCK → increased pancreatic enzyme secretion → increased enzyme flow into duodenum → increased digestion of fats and protein

explain secretin’s role in pancreatic function

gastric acid enters the duodenum → small intestine releases secretin → increased plasma secretin → increased bicarb secretion form pancreas → increased flow of bicarb into duodenum → neutralization of acid in the duodenum (gastric acid)

vagal __ go from the organ to the brain

vagal ___ go from the brain back to the organ

organ to brain: afferents

brain back to organ: efferents