Endocrine Pancreas 1 Flashcards
T/F: The endocrine pancreas comprises the majority of the pancreas
FALSE - exocrine
What hormones are produced in the endocrine pancreas
insulin
glucagon
somatostatin
What tissues are insulin sensitive?
muscle
adipose tissue
liver
Insulin and glucagon regulate glucose, ______, and _____ metabolism
amino acid
fatty acid
The majority of the endocrine are _____ cells, which produce insulin
beta
65% of the pancreas are beta cells, which is ______
insulin
20% of the pancreas are alpha cells, which is ______
glucagon
10% of the pancreas are delta cells, which is ______
somatostatin
What does somatostatin do?
inhibit both insulin and glucagon release
How are delta cells dispersed in the islets?
all around
Hormones in the pancreas are secreted into _______ veins which then drain to the ________
portal vein
liver
Give an example of a hormone around the periphery of the pancreas
pancreatic polypeptide
What are the benefits of gap junctions? Where are there gap junctions between which cell types?
FAST!
alpha to alpha
alpha to beta
beta to beta
Blood supply to pancreas arranged so that __________ from each cell type _______ other cell types
venous blood
bathe
What kind of vessel enters the islet core?
arteries
What kind of vessel is distributed throughout the inlet?
capillaries
Which type of vessel converges around the rim?
veins
Islets are innervated by _____, ________, and ________ neurons
adrenergic
cholinergic
peptidergic
What are the conserved regions of insulin?
location of 3 disulfide bonds
ends of A chains
C-terminal residues of B chain
A chain has ______ aa and B chain _______ aa
21 aa
30 aa
Which chain of insulin is more important? Why?
B chain
biologically active
How many bridges link A to B chain? There is a 3rd bridge in the _____ chain
2
A chain
Insulin is synthesized as a _________ with 4 peptides. List them
preprohormone
signal peptide
A & B chains
connecting peptide (C peptide)
Proinsulin is sent to the _____, where insulin folds and _______ form
ER
disulfide bridges
The ______ packages insulin into granules and _______ (proteases) cut ______
golgi
proteases
C-peptide
When proteases cut insulin, what are the 2 products?
insulin
C-peptide! (it’s still there)
How is insulin metabolized in the liver?
enzymes break disulfide bonds
A & B excreted in urine
What is the most important stimulator of insulin secretion?
blood glucose
Glucose is transported into the beta cell via _______ transporter. Which type of diffusion?
GLUT 2
facilitated diffusion
What is glucose immediately phosphorylated by? What is a product?
glucokinase
ATP
Why is glucose immediately phosphorylated by glucokinase?
so it doesn’t leave the cell
ATP closes ______ channels. What happens?
K+ channels
depolarizes membrane
What does depolarization do during regulation of insulin secretion? It flows [into/out of] cell
opens voltage-gated Ca2+ channels
into!
What does an increase in intracellular Ca2+ cause?
exocytosis of insulin granules into venous blood
______ is secreted in equal amounts to insulin
C-peptide
T/F: C-peptide is excreted unchanged in urine
TRUE
What 2 things are used to assess beta cell function?
blood insulin
C-peptide being excreted unchanged in urine
[Oral/Intravenous] glucose causes greatest insulin response due to “______” effect
oral glucose
incretin
Oral glucose stimulates _______
release of other hormones from enteric neurons/hormone cells in GIT
stimulates insulin release
List things that stimulate insulin secretion
amino acids
keto acids
ffa
K+, Ca2+
GIP, vagal stimulation (Ach), drugs (sulfolnylurea)
GLUCAGON
List things that inhibit insulin secretion
fasting
exercise
somatostatin
leptin
What is the insulin receptor?
tyrosine kinase
Insulin receptor has 2 subunits: _____ and _____. Define them
alpha: subunits are EXTRACELLULAR, connected by disulfide bonds between alphas, and alpha to beta
beta: span the membrane
Insulin binds [alpha/beta] subunits, causing conformational change and activates tyrosine kinase in [alpha/beta] subunits
alpha
beta
What does tyrosine kinase phosphorylate?
phosphates
phospholipases
G proteins
Insulin receptor complex internalized by target cell to be ______, ________, or ________
degraded
stored
recycled
Insulin receptors ______ or ______ regulate. Type II diabetes and obesity relate to ________
up or down regulate
down regulate
When nutrients are available, ____ makes sure those nutrients are stored
insulin
What is used during fasting?
stored nutrients
Insulin DIRECTLY stimulates glucose uptake into ______ and _______, but NOT ______
muscle
fat
NOT liver
What are some insulin-independent transporters?
GLUT 1
GLUT 2
GLUT 3
Where is GLUT 1 found?
liver
red blood cells
What helps with phosphorylation of glucose in the liver?
insulin
Where is GLUT 2 found?
liver
beta cells of pancrease
What happens in chronic hyperglycemia?
see decreased number of GLUT 2 on beta cells which decreases insulin secretion
Where is GLUT 3 found?
in brain
What are insulin-dependent transporters?
GLUT 4
Where is GLUT 4 found?
fat
muscle
heart
T/F: Transport of glucose in intestines and kidneys is NOT regulated by insulin but is K+ dependent
FALSE - NA+
Where is GLUT 5 found?
intestine