Pancreas Flashcards
How many peptide hormones does it secrete?
5
What are the peptide hormones?
- insulin
- glucagon
- somatostatin
- pancreatic peptide
- ghrelin
What is produced by beta cells?
Insulin
What is produced by alpha cells?
Glucagon
What is the function of insulin and glucagon?
Regulate glucose, FA and AA metabolism
What is produced by gamma cells?
Somatostatin
What is produced by F cells?
Ghrelin
What are islets of langerhans?
Clusters of endocrine cells in the pancreas
What is the mass of islets?
1-2%
4 cell types of islets
- alpha
- beta
- gamma
- PP
Where are alpha islets cells found?
Outer rim
where are beta islet cells found?
central core
where are gamma islet cells found?
interspersed
what is the most abundant islet cell?
Beta
blood supply of communication islets
venous blood of 1 cell type bathes the other cell types
neural innervation of islet cells
sympathetic and parasympathetic
examples of sympathetics in islet cells
adrenergic and peptidergic
examples of parasympathetic in islet cells
cholinergic and peptidergic
vagal stimulation via Ach and VIP stimulates the release of ___
insulin
where do sympathetic preganglionic cells bodies originate
intermediolateral horn cells in the spinal cord
where do sympathetic preganglionic cells synapse at with postganglionic fibers
paravertebral ganglia and celiac ganglia
what does the activation of pancreatic sympathetic nerve fibers cause stimulation of?
glucagon
what does the activation of pancreatic sympathetic nerve fibers cause inhibition of?
insulin release
a rich complement of ___ joins the splanchnic nerve and enters the spinal cord
sensory fibers
insulin is synthesized and secreted by
beta cells
what is the hormone to be isolated from animal sources in a form that could be administered to humans
insulin
what hormone is measured by RIA
insulin
what hormone is known to be synthesized from a larger precursor
insulin
main parts of an insulin structure
a chain, b chain and a bridge to connect the chains
which chromosome is insulin synthesized on
11
where is the metabolism for insulin at
liver and kidneys
separate a and b chains are ___ excreted in urine
inactively
a signal peptide for preproinsulin is cleaved when
early
preproinsulin has a ___
connecting peptide (C peptide)
what is proinsulin
preproinsulin minus the signal peptide
where does proinsulin travel to
ER
C peptide is removed by ___
proteases
C peptide is the basis for the test of type ___ diabetes
1
the C peptide levels reflect ___ function in people with type 1 diabetes
beta cell
stimulatory factors affecting insulin secretion
increase in glucose, AA, FA concentrations, ketones, cortisol, GIP, GLP1, K+, vagal stimulation (Ach), sulfonylurea drugs, obesity, b-adrenergic agonists, GH/prolactin, glucagon
inhibitory factors affecting insulin secretion
decrease in glucose concentration, fasting, exercise, somatostatin, EP, NE, IGF1, leptin, diazoxide
t/f: c peptide is secreted in equimolar amounts with insulin and is excreted unchanged in the urine
true
t/f: intravenous glucose does cause the release of GIP
false- only acts directly
what are incretins
group of GI tract hormones that cause an increase insulin release after eating
what are 2 major incretins
GIP and GLP
a ___ rate of stomach emptying decrease food intake
slow
other factors affecting insulin secretion
FAs and Has use metabolic pathways, drugs to treat type 2 diabetes, closing K+ channels
what does insulin bind to on a receptor
alpha subunits
insulin activates ___ in the beta subunit which phosphorylates itself in the presence of ATP
tyrosine kinase
what is the insulin-receptor complex internalized by
endocytosis
insulin is either ___ or ___
degraded or stored to be used again
how does insulin down regulate its own receptor
by decreasing the rate of synthesis and increasing the rate of degradation
what is the hormone of abundance
insulin
when are excess nutrients stored
when the availability > body demands insulin
where is glycogen stored
liver
where is fat stored
adipose tissue
where is protein stored
muscle
actions of insulin
decrease blood glucose concentration, decrease blood FA and ketoacid concentration, decrease blood AA concentration, promotes K+ and glucose uptake, direct effect on satiety center
from where is the satiety center stimulated
ventromedial nucleus in the hypothalamus
how does insulin decrease blood glucose
getting transported to target cells via GLUT4
a decrease in blood glucose promotes ___
the formation of glycogen and inhibits glycogenolysis
t/f: the liver does not require insulin for glucose uptake
true
low blood glucose inhibits ___
gluconeogenesis
how does insulin decrease blood FA and ketoacids
by decreasing their concentrations
how do you decrease blood FA and ketoacid concentrations
inhibit the mobilization and oxidation of FA and increase storage
adipose inhibits ___
lipolysis
liver inhibits ketoacid formation by ___
decreasing FA degradation
how does insulin decrease blood AAs
increase AA and protein uptake, increase protein synthesis and decrease protein degradation
what are the tissues that don’t need insulin for glucose uptake
BRICKLE
brain, RBCs, intestine, cornea, kidney, liver, exercising skeletal muscle
is GLUT2 insulin dependent
yes
how does glucose enter pancreatic beta cells
via GLUT2
which type of diabetes is insulin dependent
1
what is type 1 diabetes characterized by
destruction of beta cells, loss of lean body mass and adipose, glucosuria, hyperkalemia
characteristics of type 2 diabetes
insulin resistance of target tissues, associated with obesity
what is type 2 diabetes caused by
down regulation of insulin receptors and insulin resistance
in t2d, normal insulin concentrations cannot ___
activate receptors
the main treatment for t2d is ___
exercise
incretin effect on oral glucose tolerance test
GLP1
graph over oral glucose tolerance test
a normal person’s blood glucose will decrease throughout the day after they wake up. someone with diabetes will have a constant increase in blood glucose after they wake up
what is glucagon synthesized by
islet alpha cells
what is the opposite of insulin
glucagon
what is the hormone of starvation
glucagon
function of glucagon and other fuel-mobilizing hormones
counterbalance the fuel-storing effects of insulin
t/f: states of glucagon excess or deficiency always lead to overt disease due to other hormonal compensation
false- rarely
what do peptides include
GI hormones, secretin and GIP
what is glucagon synthesized as
preproglucagon
how is preproglucagon stored
in dense granules
stimulatory factors affecting glucagon secretion
fasting, decrease glucose concentration, increase AA concentration, CCK, EP, NE, Ach, GIP
inhibitory factors affecting glucagon secretion
glucose, insulin, somatostatin, increase FA and ketoacid, GLP1
what are the actions of glucagon
maintains blood glucose in the fasting state, increase glycogenolysis, glucogenesis, lipolysis, FA, ketoacids
what is the most important function of glucagon
stimulates the liver to produce and secrete glucose and ketone bodies
physiologic actions of glucagon
stimulates a hepatocyte to produce glucose, glycogenolysis, inhibits the formation of glycogen from glucose, gluconeogenesis, lipogenesis, ketogenesis, ureogenesis
where are amino groups removed
in urea
what is the most important determinant of glucagon secretion
concentration of glucose
at what level of secretion is glucagon maximally inhibited
> 200
___ inhibits glucagon secretion
insulin and FFA
when is glucagon secreted
by a protein rich meal
function of glucagon
prepares the liver for gluconeogenesis and signals the liver to release glucose
what is somatostatin secreted by
gamma islet cells
what inhibits somatostatin
insulin
pancreatic somatostatin inhibits the secretion of ___
insulin and glucagon
function of somatostatin
modulate or limit the responses of insulin and glucagon to ingestion of food
what is pancreatic polypeptide secreted by
F cells
function of PP
self-regulate the pancreas’s secretory activities
when is pp secreted
after a protein meal
when is ghrelin secreted
in between eating
where is ghrelin produced
stomach mucosa, pancreas, brain, ovary, adrenal cortex
function of ghrelin
increases feelings of hunger, increases gastric acid secretion, gastric motility and gastric emptying
what is the only hormone that promotes food intake
ghrelin
