3. Endocrine Pancreas Flashcards
What do the endocrine cells of the pancreas secrete
Insulin
Glucagon
Somatostatin
How are the endocrine cells of the pancreas arranged
Clusters called Islets of Langerhans
In the Islets of Langerhans where are alpha and beta cells located and what do they secrete
Beta cells- centrally located and secrete Insulin and C peptide
Alpha cells- peripherally located and secrete glucagon
What are the functions of d and f endocrine pancreas cells
d- secrete somatostatin
F- act like a satiety signal
How is blood supplied to islets of langerhans
- Islets receive 10% of pancreatic blood flow
- blood flows first to center (for insulin) and then to periphery
- Paracrine actions work in reverse of blood flow
What is the major stimulatory factor of insulin secretion
Glucose
What is used as an endogenous insulin secretion marker
C peptide
-Insulin and cleaved C peptide are packaged together in secretory vesicles
How does Glucose get into the cell in order for insulin to be released
Glut-2
What is the target for treatment of Type 2 DM
Sulfonylurea receptors associated with ATP-dependent K+ channels
Insulin release is biphasic, how does that relate to patients with DM
Diabetic individuals lose first phase in insulin secretion
What does AMP-kinase (AMPK) have to do with uptake of glucose
Activation of AMPK results in GLUT4 translocation to plasma membrane
(muscle contractions stimulate this process)
What stimulates insulin secretion
- Increased glucose concentration
- Increased amino acid concentration
- Glucagon
- Cortisol
- Potassium
- Obesity
What inhibits insulin secretion
- Decreased blood glucose
- Fasting
- Exercise
- Somatostatin
- Norepinephrine
What does insulin do to skeletal muscle
- Increase glucose uptake
- Increase glycogen synthesis
- Increase glycolysis and CHO oxidation
- Increase protein synthesis
- Decrease protein breakdown
What does insulin do to the liver
- Promotes glycogen synthesis
- Increases glycolysis and CHO oxidation
- Decreases gluconeogenesis
- Increase in hexose monophosphate shunt and pyruvate oxidation
What does insulin do the adipose tissue
- Increase glucose uptake
- Increase glycolysis
- Decrease lipolysis
- Promote uptake of fatty acids
How is glucagon synthesized and where is it stored
- Made as preproglucagon
- stored in dense granules of alpha cells
What is the major stimulant for secretion of glucagon
Decreased blood glucose
What are the major actions of glucagon on the liver
- Increase blood glucose
- Increase gluconeogenesis
- Increase glucogenolysis
- Inhibit glycogen synthesis
Describe Type 1 DM (juvenile onset diabetes)
Inadequate Insulin Secretion
- Destruction of B cells
- Decreased utilization of ketoacids results in DKA
- Hyperkalemia (shift of K+ out of cells)(plasma levels may be normal)
- Osmotic Diuresis / Glucosuria
What is Insulin Resistance
Progessive exhaustion of active B-cells
sedentary lifestyle, malnutrition or obesity
What is Reactive Hyperinsulinemia
- Decreased GLUT4 uptake of glucose in response to insulin
- Decreased ability of insulin to repress hepatic glucose production
- Inability of insulin to repress adipose tissue uptake and lipolysis
What is the incretin effect
Type 2 diabetics have a reduced incretin effect
