Pancreas Flashcards
what hormones are secreted by the pancreas?
- insulin
- glucagon
- somatostatin
- pancreatic polypeptide
- amylin
what is the target organ for pancreatic hormones?
liver
what aspects of the parasympathetic NS innverate the pancreas?
the vagus nerve stimulates glucagon, somatostatin, insulin, and pancreatic polypeptide secretion.
also Ach and other ntrans act on it
what sympathetic NS ntrans innervate the pancreas?
NE, galanin, NPY
what are the islets of langerhans?
small clusters of endocrine cells in the pancreas. they are made up of many cell types including alpha, beta, delta, epsilon, and PP cells that secrete different products.
which cells of the islets of langerhans secrete glucagon and which secrete insulin?
alpha: glucagon
beta: insulin
what is the role of endopeptidase?
cleaves proinsulin to create active and final insulin product
what is the half life of insulin?
5 minutes
how can you determine how much endogenous insulin one has circulating in their body?
look at C peptide levels
when is insulin at its peak levels?
1 hour after meal
what does “biphasic release of insulin” mean?
phase 1: a rapid initial release of premade insulin
phase 2: (like 5-10 min later) a sustained release of newly made insulin over an hours time
what is pulsatile release of insulin
the biphasic release after a meal
what is the major stimulant of insulin release?
glucose
how does glucose cause insulin release?
- glucose enters B cells via GLUT2
- ATP is made in TCA
- ATP blocks the efflux of K+ which depolarizes the cell
- Ca++ voltage channels open in response and Ca++ enters the cell
4b. PLC and AC can trigger Ca++ release from intracellular stores - Ca++ triggers the exocytosis of insulin secretory granules and insulin is released into circulation
what kind of receptor is the insulin receptor?
receptor tyrosine kinase
what is IRS?
insulin receptor substrates that are phosphorylated
what are the two major insulin signaling pathways?
- MAPK (RAS TO ERK)
2. IP3
how does insulin affect the liver?
induces:
1. glycogen synthesis
2. cholesterol synthesis
3. lipogenesis
inhibits
1. glycogen break down
2. gluconeogenesis
3. lipolysis
how does insulin affect the hypothalamus?
induces- energy expenditure
inhibits: appetite
how does insulin affect the adipose tissue and skeletal muscle?
Induces: 1. glucose uptake 2. glycogen synthesis 3. glycolysis 4. lipogenesis 5. protein synthesis inhibits 1. lipolysis 2. glycogen breakdown 3. fatty acid oxidation
what are the 3 phase of insulin effects and what happens in each phase?
- rapid (in sec)
increases glucose, AA, and K+ transport into insulin senstive cells - intermediate (minutes)
metabolic changes: make glycogen, proteins, etc. - delayed (hours)
increase mRNAs for metabolic processes
how is insulin signaling deactivated? 5 ways
- Insulin disengages from receptor
- receptor is degraded
- receptors are deactivated by phosphatases
- SOCS block the intxns btwn IR and insulin or degrade IRS
- serine kinases block signaling
what are 4 ways insulin receptors are downregulated?
- diet
- chronicly high insulin levels
- obestiy
- excess GH
where is GLUT2 located?
B cell in islets, liver, intestine, kidney
where is GLUT4 located?
skeletal muscle, adipose tissue, and cardiac muscle
what is GLP1 and what does it do?
it is glucagon like peptide and it increases insulin secretion
GLP2 role?
GLP2 is made in the brain and stops you from eating
what stimulates glucagon secretion?
- drop in blood glucose
- drop in insulin
- exercise
- gatric inhibitory polypeptide
- Epi, DA, NE
what inhibits glucagon secretion?
- high blood glucose
- somatostatin
- fatty acids
- GABA
how does glucagon stimulate gluconeogenesis?
- glucagon binds to its Gpcr
- AC makes cAMP
- PKA is increased
- other factors signal to start process
what does somatostatin do?
inhibits GI exocrine and endocrine functions.
pancreatic polypeptide
released after eating and exercise
inhibits pancreatic exocrine secretion and other GI functions
regulates feeding behavior
amylin
regulates plasma glucose concentrations
suppresses glucagon
slows gastric emptying
activates glycolysis
what are the 3 hormone producing tumors?
- insulinoma (too much insulin made)
- glucagonomas (too much glucagon made)
- somatostatinoma