Lecture 9: Pancreas Flashcards
The exocrine cells of the pancreas are
acinar and duct
beta cells make and secrete __________
insulin
glucagon is made by ________
alpha cells
Somatostatin is made by _________
delta cells
What do PP cells make?
pancreatic polypeptide (inhibit acinar cells)
What are the 2 major pancreatic hormones?
1) Insulin (anabolic)
2) Glucagon (catabolic)
What are the 4 minor pancreatic hormones?
1) somatostatin
2) amylin
3) pancreatic polypeptide
4) ghrelin
How many islets does the human pancreas have?
1 million
What kind of capillaries populate the pancreas?
fenestrated
Beta cells are clustered in the _______ while other cells are in the _________
core (surrounded by alpha cells); mantle (near vasculature)
True or false: glucagon has a direct effect on the beta cell to influence insulin
FALSE (paracrine effects only)
How does blood flow to the islet?
arteriole projects into center of islet, insulin rich blood flows from center to periphery of islet
What is the half life of insulin?
3-8 mins (VERY short)
What is the half life of C-peptide?
35 mins (used as indicator of pancreatic function)
Why is the cleavage of C peptide so critical?
exposes end of insulin chain that interacts with receptor
What peptides make up insulin?
A and B chains
What is the first step in insulin release?
1) glucose outside the beta cell stimulates insulin production
GLUT-2 receptor senses high glucose (has low affinity for glucose so only detects high conc. allowing glucose into the cell)
Once glucose enters the beta cell, what happens?
glucokinase phosphorylates glucose which traps it into the cell
What is the pancreatic glucose sensor?
glucokinase (not activated unless glucose is high)
What is the second step in insulin release?
2) glucose inside beta cell (glucose is phosphorylated by glucokinase —— G6P generates ATP)
What is the third step of insulin release?
3) glucose metabolism
increased ATP closes K+ channels (as do sulfonylurea drugs since K+ channels have a SUR subunit)
How do sulfonylurea drugs work and what are they used for?
close the potassium channels (used as the earliest antidiabetic drugs) and bypass glucose step
What is the benefit to the K+ channels closing?
holds more K+ inside the cell causing it to depolarize (influx of sodium into the cell)
What is the 4th step in insulin release?
cell depolarization
closing K+ channels depolarize cell which opens the Ca++ channels