Endocrine Pancreas: Insulin and Glucagon Flashcards
The Islets of Langerhans in the pancreas contain what cell types
Alpha, Beta, Delta, F cells
Alpha cells in the islets do what?
Glucagon synthesis
Beta cells in the islets do what?
Insulin Production
Delta cells in the islets do what?
Somatostatin
F cells in the islets produce what?
Pancreatic polypeptide
Where do the alpha cells tend to be located within the islet?
The outside of the cell
Where do the beta cells tend to be located within the islet?
The inside of the cell. Delta cells tend to be in between
What does somatostatin do in the pancreas?
We know that somatostatin is an inhibitory hormone. It inhibits insulin and glucagon production in the pancreas. Works in a paracrine fashione
Insulin synthesis
Proinsulin –> insulin + C peptide
B cells make highly electron dense granules
KNOW
Know that insulin and C- peptide are both packaged into granules and that they are both dumped out in equal molar amounts
truth.
This can sometimes be important clinically. For example, if you have a pt who is insulin dependent but may have some residual B cell function and you want to know how much…you can measure C-Peptide level
Major stimuli for insulin secretion?
Increase in Plasma glucose
Increase in plasma amino acids
Increase in GI hormones
Increase in Parasympathetic NS (Ach)—Better absorption (insulin) when you aren’t stressed
Decrease in sympathetic
Major stimuli for glucagon relase
Decrease in plasma glucose
Increase in plasma amino acids- (If you eat a steak with no bread, so high protein with no carbs, your amino acid levels will rise which will stimulate insulin release and your glucose will plummet. The release of GLucagon prevents sudden hypoglycemia
Do you see changes in peripheral glucagon levels after a big meal?
NO!!! It mostly goes to the liver.
KNOW
Insulin release occurs in what pattern?
Rapid oscillations
Insulin half life?
about 5 minutes
Glucagon half life?
5-10
Most of insulin degradation occurs where?
Kidney and liver
Glucagon degradation occurs where
most occurs in the liver
KNOW! Both hormones, insulin and glucagon, first go to the liver. Large amounts of each are extracted by the liver and exert their actions there. Much of these secreted hormones is also degraded by the liver so it never gets out to the rest of the body
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Whereas Glucagon’s major target tissue far and away is the liver, the major target tissues for insulin are:
Muscle, Liver, Adipose (three largest tissue sin the body)
KNOW: What tissues does insulin not stimulte glucose uptake
Brain
Intestinal mucosa
Red Blood Cells
Kidney Tubules
What is the main role of glucagon
Promotes glucose release from the liver- to maintain normal plasma glucose conc
Hepatic actions of glucagon are?
Glycogenolysis inc
Increase in amino acid uptake
Increase in gluconeogenesis
Increase in ketoneogenesis
Glucagon and catecholamines need prior action of what to function optimally in the liver?
Cortisol
What are some important enzymes altered by Glucagon?
- Inc in phosphorylase activity
- decrease in glycogen synthetase activity
Insulin is the most potent storage hormone
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Major role of insulin>
Promotes the synthesis of each of the three main nutrient storage forms: Protein, carbs, fats
Look at the major actions of insulin
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What are the effects of Growth hormone on onsulin release and sensitivity of target tissues
Increases insulin release but decreases the sensitivity of target tissue
What are the effects of cortisol on insulin release and sensitivity of target tissues
Increases insulin release but decreases sensitivity
What are the effects of T3 on insulin release and sensitivity of target tissue
T3 increases insulin release and increases sensitivity of target tissues.
