Flashcards in Physio - Hu - Insulin and Glucagon AND Regulation of Apetite - 2/17 Deck (34)
Insulin is produced by what cell type?
Beta cells, in the islets of Langherhans of the pancreas.
When is glucagon released?
Because it is a catabolic hormone (insulin is anabolic), it is released during times of food deprivation., exercise, stress, and in response to increased levels of alanine and arginine
What hormones allow the utilization of stored nutrient reserves by mobilizing glycogen?
Glucagon, epi, norepi
What hormone inhibits the release of insulin and glucagon, as well as gastrin, gastric acid secretion and gut hormones?
Somatostatin, produced by delta cells which are dispersed at the periphery of the islets.
**Somatostatin is the primary inhibitor of insulin.
Alpha cells produce what hormone?
Glucagon, produced by alpha cells at the periphery of the islets.
What is pancreatic polypeptide?
A gastro-intestinal hormone produced by F cells, located in the periphery of the islets. Pancreatic polypeptide inhibits gallbladder contraction and pancreatic exocrine secretion. It's active during strenuous exercise, after a high protein meal or during periods of hypoglycemia
Glucagon is inhibited by what:
Why do counter-regulatory hormones, such as growth hormone, glucagon, cortisol and catecholamines, get released in times of stress/exercise/food deprivation?
To maintain glucose to the brain
The primary target of glucagon is the ____. What does it do there?
Liver, where glucagon antagonizes insulin, stimulated glycogenolysis, and gluconeogenesis, increases lipolysis
In adipose tissue, what is the role of glucagon?
Decreases glycolysis, promotes lipolysis and release of fatty acids
How is insulin produced and processed?
Insulin is produced in beta cells, as pro-insulin with endopeptidase. Endopeptidase has activity similar to trypsin. Proinsulin and endopeptidase are secreted together. Proinsulin is cleaved and becomes C peptide and insulin, C-peptide has no biological activity, but can be used as a marker for endogenous insulin production.
When do levels of blood glucose and insulin spike after a meal?
Why is insulin response to glucose a spike, followed by more modest maintenance of levels?
First, stored insulin is released, then the body needs to make more insulin
What are the 7 steps in insulin secretion by beta cells?
1. Glucose enters cell via GLUT2 transporter (facilitated diffusion)
2. Glucose metabolism occurs, leading to increase in ATP
3. ATP inhibits the ATP-sensitive K-channel.
4. Inhibition of K channel causes depolarization.
5. Depolarization activates voltage-gated Ca channel (influx of Ca)
6. Increased Ca through channel induced Ca-induced Ca release from ER.
7. Elevated Ca causes release of packets of insulin via exocytosis.
**Other modulators than glucose act via adenylate cycclase-cAMP-pKA/pKC pathways
Explain the two phases of insulin response after feeding.
Cephalic phase - gastric acid secretion and small rise in plasma insulin mediated by Mr. Vagus.
Intestinal phase - glucose absorption and rise in plasma glucose is primary stimulus for insulin secretion.
What are incretins?
CCK, GIP (gastric inhibitory peptide), GLP-1 (glucagon-like peptide)
These provide advance notice of feeding and stimulate insulin secretion (oral glucose more effect than IV glucose)
What are the anabolic actions of insulin on an adipocyte?
1. Glucose uptake via GLUT-4
2. Glucose participate in increased glycolysis
3. Glycolysis produces alpha-glycerophosphate
4. alpha-glycerophosphate increases esterification of fats
Lipolysis is decreased
Stimulates synthesis of lipoprotein lipase which moves to the surface of endothelial cells where it releases fatty acids from chylomicrons and VLDL.
How do diabetic perform in glucose tolerance tests?
The glucose hangs around for a lot longer in the blood be there is impaired/less uptake. Dx of diabetes if glucose >200 after 2 hours
Sympathetic stimulation would have what effect on insulin secretion?
Many hormones stimulate insulin secretion. Name 5.
Serum free fatty acids, ie ketoacids, and serum ketone bodies, would have what effect on insulin secretion?
During exercise, circulating epinephrine stimulates insulin secretion via a __1___ on the pancreatic beta cell. But, local autonomic adrenergic innervation releasing norepinephrine acts via ___2___ and predominates
1. Beta receptor
2. Alpha receptor
What are the anabolic actions of insulin on the liver?
1. Insulin stimulates glucose uptake, and decreases glucose output.
2. Insulin stimulates the formation of glycogen.
3. Insulin inhibits glycogenolysis
4. Insulin promotes glycolysis and lipogenesis
5. Insulin decreases fat oxidation, gluconeogenesis and ketogenesis.
6. Insulin promotes protein synthesis and inhibits protein breakdown and the urea cycle.
What are the anabolic actions of insulin on muscle?
1. Insulin stimulates glucose uptake via GLUT-4
2. Insulin promotes glycogenesis and inhibits glycogenolysis.
3. Insulin promotes glycolysis, supplying acetyl-CoA for fatty acid synthesis and lipogenesis
4. Insulin stimulates amino acid uptake and protein synthesis and decreases proteolysis.
Give two methods of developing insulinemia.
1. IV insulin or shots
What is the effect of a glucagonoma?
Hyperglycemia, elevated levels of glucagon in the blood.
What is neuropeptide Y?
Neurotransmitter that stimulates feeding, aka orixigenic factor (hypothalamus)
Corticotropin releasing hormone (CRH), GLP-1, alpha-melanocyte stimulating hormone (alpha-MSH) and cocaine and amphetamine-regulating transcript (CART) are all examples of:
Anorexigenic factors, neurotransmitters that inhibit feeding (hypothalamus and NTS in hindbrain)
T/F: Both leptin and insulin can cross the BBB.
True, they can cross the BBB and travel to the hypothalamus to influence energy homeostasis.