Flashcards in Physiology of the Pancreas Deck (39)
What surrounds the pancreas on the right?
- the 1st, 2nd, and 3rd parts of the duodenum
Can stones work their way into the pancreatic duct from the common bile duct?
- YES, preventing secretions, leading to self digestion and thus inflammation (pancreatitis).
What regulates the pancreas?
- What sphincter relaxes allowing both pancreatic and gall bladder secretions to the duodenum?
- sphincter of Odi
What type of glands are seen on histology in the pancreas?
- compound glands (islets of langerhans, beta, alpha, and delta cells).
What 2 general functions does the pancreas have?
What are the functions of the ENDOcrine pancreas?
- insulin= decreases blood glucose by allowing glucose get into the cells following a meal.
- glucagon= increases blood glucose by increasing glycogenolysis and gluconeogenesis.
What are the digestive enzymes released by the pancreas?
- trypsin, chymotrypsin= breaks down proteins
- carboxypeptidase= yields individual amino acids
- pancreatic lipase= breaks down fats
- pancreatic amylase= breaks down carbs
What other EXOcrine secretions are released by the pancreas?
- sodium bicarb (NaHCO3) to buffer the acidic pH from the gastric contents entering the duodenum.
What is the role of the pancreas in energy?
- provides a means for chemical reactions to extract energy from ingested foods.
**** What enzyme activates trypsinogen to trypsin?
*trypsin then activates chymotrysinogen and procarboxypeptidase.
What is the function of trypsin inhibitor?
- inhibits pancreatic digestion of itself (i.e. prevents autodigestion of the pancreas; acute pancreatitis).
What is the role of carbonic anhydrase?
- forms carbonic acid by combining H2O and CO2.
What stimulates pancreatic secretions?
- acetylcholine (from nervous innervation and bloodstream)
- cholecystokinin (I cells)= causes gallbladder to contract and proteases to be released from the pancreas.
- secretin= released by the duodenum (especially in response to acidity) to stimulate pancreatic sodium bicarb production.
What are the phases of pancreatic secretion?
1. cephalic= thinking of a meal
2. intestinal= secretin mediated.
What cells make up the islets of langerhans?
- alpha cells (25%)= glucagon
- beta cells (60%)= insulin
- delta cells (10%)= somatostain (inhibits insulin/glucagon)
What other hormones are secreted by the pancreas?
- amylin= inhibits insulin secretion
What are the main roles of the pancreas in energy production?
- glucose metabolism/glycogen storage
- fat metabolism
- tissue metabolism/tissue amino acid uptake
How is insulin produced?
- proinsulin (inactive form) to insulin (active form) via insulinase (10-15 min clearance from blood via the liver, kidney, and muscle).
How does insulin work?
- 2 alpha and 2 beta subunits.
- autophosphorylation on beta units takes place intracellularly.
- phosphorylation of insulin-receptor substrates (IRS)
- INCREASED CELLULAR UPTAKE of GLUCOSE
*increased permeability of K+ through membrane + amino acids.
**** What are the effects of insulin?
- increased muscle glucose uptake and metabolism.
- increased storage of glycogen in muscle.
- increased membrane glucose transport.
- increased liver uptake and storage of glucose (activation of liver phosphorylase, increase glucokinase activity, increased glycogen synthetase activity).
- increased conversion of glucose into fatty acids.
- inhibition of gluconeogenesis in the liver, aa less available due to muscle storage.
Does insulin promote fat synthesis and storage in adipose tissue?
What does inhibition of hormone sensitive lipase do?
- blocks FFA release into blood.
*aka less fat hydrolysis and more fat build up with insulin.
**** What can lack of insulin lead to?
- increased use of fats (increased plasma cholesterol and phospholipid levels), leading to KETOSIS and ACIDOSIS!
Does insulin cause inhibition of protein catabolism or anabolism?
- protein catabolism
What does insulin do to GH?
- enhances GH
What stimulates insulin secretion?
- elevated blood GLUCOSE
- elevated FFA in blood
- elevated AA blood levels
- GI hormones (gastrin, CCK, secretin, GIP)
- glucagon, GH, cortisol
- B-adrenergic stimuli
- sulfonylurea meds (glyburide/tolbutamide)
What DECREASES insulin release?
- alpha-adrenergic stimulus/ leptin
What does glucagon do? (TEGRITY)
- helps bring blood glucose levels by increasing glycogenolysis, gluconeogenesis, and adipsoe cell lipase via cAMP...
*glucagon is released from alpha cells.