Endocrine System: Pancreatic Hormones

What hormones are secreeted by the endocrine pancreas?

-insulin

-glucagon

-somatostatin

-pancreatic polypeptide

What are the islets of Langerhans?

cluster of endocrine secretory cells in the pancreas

What cells secrete insulin?

beta cells

What cells secrete glucagon?

alpha cells

What cells secrete pancreatic polypeptide?

F cells

What cells secrete somatostatins in the pancreas?

delta cells

How do islet cells communicate to eachother?

-gap junctions

-capillaries within the islet

-intraislet neural communication

What type of hormone is insuline?

peptide

What is the structure of insulin?

two straight chains of amino acids with two disulfide bonds between and one internal disulfide bond within the A chain

What is secreted from beta cells?

-insulin

-connecting peptide

What is the connecting peptide? Why is it important?

byproduct of insulin production that is secreted at the same time as insulin

-it does not get used by the body so it is a good indicator for status of insulin production by the body

What is endogenous beta cell function test?

measures the serum concentration of connecting peptide to get better idea of how the insulin system is working

What is the most important factor that influences insulin?

glucose levels

What is insulin hormone known as?

the hormone of abondance

-too much glucose stimulates insulin

How does glucose gain access to beta cells?

binds to GLUT 2 transporter

What is the effect of glucose once inside beta cells?

signals for the release of preformed insulin

How is insulin secretion regulated ?

1) increased levels of glucose in blood

2) glucose binds to GLUT 2 transporter

3) glucose inside of cell produces ATP

4) ATP gated K+ channels close due to excess ATP

5) K+ is stuck in cell causing depolarization

6) depolarization causes voltage gated Ca2+ channels to open

7) calcium binds to vesicles stimulating insulin release

What facors stimulate insulin secretion?

-INCREASED GLUCOSE CONCENTRATION

-increased amino acid concentration

-glucagon

-growth hormone

-cortisol

-gastric inhibitory peptide

-potasium

-vagal stimulation

-sulfonylurea drugs

-obesity

What is gastric inhibitory peptide hormone?

secreted by the gut in response to digesting glucose

What is the effect of sulfonylurea drugs?

attempt to drive insulin production by increasing ATP production

WHat factors inhibit insulin secretion?

-decreased blood glucose

-fasting

-exercise

-somatostatins

-alpha adrenergic agonists

-diazoxide

What is the receptor for insulin?

receptor tyrosine kinase

What is the effect of insulin binding to its receptor?

1) insulin binds to RTK

2) dimerization occures with adjacent receptors

3) activation of kinase domain

4) beta subuint auto phosphorylates

5) activate catalytic activity

6) phosphoryation of IRS

7) recruitment and activation of intracellular enzymes and regulation of gene expression

What are insulins functions in the liver?

-promote storage of glucose as glycogen

-promotes triglyceride formation from fatty acid and glycerol

-inhibits ketoacid formation

How does insulin promote glucose storage in the liver?

increases the GLUT 2 trasporter expression on liver to stimulate glucose movement into the cell

-inhibit glycolysis

How does insulin promote triglyceride formation in the liver?

-inhibits gluconeogenesis so excess glycerol is bound to fatty acids to form triglycerides

-triglycerides are trasported through blood to adipose tissue

How does insulin inhibit ketoacid formation?

ketoacids are formed by the metabolism of fatty acids making the blood acidic

-insulin atimulates acetyl-CoA carboxylase to convert acetyl CoA to malonyl CoA

-manonyl CoA inhibits enzyme responsible for bringing fatty acid to the mitochondria

What are the effects of insulin on adipose tissue?

-promote GLUT 4 transporter expression

-promote fat storage in adipose tissue

Where is GLUT 4 transporter found? What is its role?

in adipose tissue

-it binds to triglycerides and glycerol and transports them into cell for storage

How does insulin stimulate fat storage in adipose tissue?

-increase mobility of triglycerides and fatty acids from the liver

-promotes conversion of glucose to glycerol

-promots synthesis of triglycerides

-inhibits lipolysis

-promotes GLUT 4 transporter

What is the effect of insulin on skeletal muscle?

-promote glucose storage as glycogen

-promote protein synthesis and storage

How does insulin promote glucose storage in skeletal muscle?

-increase GLUT 4 transporter expression

-stimulate glycolysis in muscle cells for ATP synthesis

-promote glycogenesis

How does insulin promote protein synthesis?

-promotes amino acid transport into muscle

-inhibits protein degredation and metabolism

What are other functions of insulin throughout the body?

-increase potasium uptake by cells

-stimulate hypothalamic satiety center

What is glucagon known as?

the hormone of starvation

What type of hormone is glucagon?

peptide hormone

What inhibits glucagon synthesis?

-glucose

-insulin

Which is stronger glucagon or insulin?

insulin

What regulates glucagon secretion?

-decreased glucose levels

-decreased insulin levels (insulin is an inhibitor of glucagon)

-exercise and fasting promote glucagon secretion

What is the strongest stimulant for glucagon secretion?

low blood glucose levels and reduced insulin

What are the effects of glucagon on the liver?

-promotes glycogenolysis

-inhibits gluycogenesis and glyolysis

-promotes lipolysis releaseing free fatty acid

-inhibits acetyl-CoA carboxylase

-promotes ketoacid formation

What type of hormone are somatostatins?

peptide hormone

What is the role of somatostatin?

inhibits glucagon and insulin secretion

What is the effect of insilin on somatostatin?

inhibits somatostatin secretion

What other structure in the body produces somatostatin?

hypothalamus