Metabolic Effects of Glucagon and Insulin Flashcards
What four organs play a dominant role in fuel metabolism?
- liver
- adipose tissue
- muscle
- brain
(don’t work in isolation but in network with each other)
Each of the four main organs is specialized for what three things?
- storage
- use
- generation of specific fuels
What two hormones control the integration of energy metabolism?
insulin and glucagon
What two hormones play a supporting role in integration of energy metabolism?
epinephrine and norepineprine
What polypeptide hormone is produced and secreted by the beta cells of the islets of Langerhans?
- insulin
Insulin’s metabolic effects are ____.
anabolic
True or False? Insulin and glucagon release is always coordinated?
True
Insulin synthesis and secretion are stimulated by what three things?
- glucose
- amino acids (especially arginine)
- gastrointestinal hormones (secretin)
What is the most important stimulus for insulin secretion?
glucose
What inhibits insulin secretion?
- scarce dietary fuels
- stress (fever or infection)
- epinephrine (trauma or extreme exercise)
What three tissues are the effects of insulin most prominent?
- liver
- muscles
- adipose
How does insulin effect the liver?
inhibits gluconeogenesis and increases glycogen synthesis
How does insulin effect the muscles?
increased glycogen synthesis, glucose uptake by increasing the number of transporters
How does insulin effect adipose tissue?
increased glucose uptake
What does insulin do?
decreases blood glucose
_____ causes a significant reduction in the release of fatty acids.
Insulin
Insulin _____ triacylglycerol degradation and ______ triacylglycerol synthesis.
decreases, increases
True or False? Insulin causes the uptake of glucose to be stored as glycogen in the liver and muscles or as triacylglycerol in adipose tissue.
True
Insulin binds to high affinity receptors that have alpha and beta subunits. What do the alpha and bet subunits do?
beta subunit: hydrophobic and contains tyrosine kinase that is activated by insulin
alpha subunit: insulin binding site
How does insulin effect membranes?
GLUT-4 transporters are recruited
True or False? Some tissue do not require insulin for glucose transport?
True
How does the insulin receptor regulate insulin?
It downregulates it by endocytosing the receptor containing the bound insulin
How long does it take for GLUT-4 transporters to increase in skeletal muscle and adipose tissue?
seconds
What polypeptide is secreted by alpha cells of the pancreatic islets of Langerhans?
glucagon
Glucagon (along with epinephrine, cortisol, and growth hormone) is considered a “_______ hormone.”
counterregulatory
What is the main job of glucagon?
it prevents hypoglycemia by initiating certain metabolic pathways
What are the three stimuli for glucagon secretion?
- low blood glucose
- amino acids (glucagon secreted with insulin to prevent hypoglycemia)
- epinephrine (during stress or exercise, glucagon is secreted in anticipation of increased glucose use)
What inhibits glucagon?
- increased blood glucose
- insulin
Glucagon increases blood glucose concentration by _____ and _____.
initiating glycogenolysis and gluconeogenesis in the liver
_____ causes hepatic oxidation of fatty acids.
Glucagon
_____ causes increased amino acid uptake by the liver.
glucagon
What is characterized by confusion, aberrant behavior and possible coma?
hypoglycemia
True or False?
Hypoglycemia symptoms can be resolved within minutes of glucose ingestion.
True
Why is hypoglycemia considered a medical emergency?
The CNS demands a constant supply of blood-borne glucose.
What two hormones are the two most important in preventing hypoglycemia?
glucagon and epinephrine
What disease includes symptoms of adrenergic and neuroglycopenia?
hypoglycemia
Receptors in what area mediate release epinephrine, ACTH, and growth hormone?
hypothalamus
What are the three types of hypoglycemia?
- insulin-induced
- postprandial
- fasting
What is insulin-induced hypoglycemia caused by?
diabetics who administer too much insulin
What causes posprandial hypoglycemia?
exaggerated insulin release following a meal
What is fasting hypoglycemia caused by?
when the liver is unable to produce adequate glucose levels during periods of fasting or by a Beta cell tumor
True or False? Hypoglycemia can result from alcohol intoxication.
True
Alcohol consumption can cause dangerous hypoglycemia in individuals who:
- have exercised strenuously for a prolonged time
- are fasting
- take insulin for diabetes
