Flashcards in Endocrine Pancreas Deck (53):
What is the function of the pancreas?
1. Both an endocrine and exocrine gland
A. Exocrine pancreas
-99% of gland
B. Endocrine pancreas
-1% of gland
What is the primary role of the pancreatic hormones?
1. Primary role is to maintain appropriate basal level of glucose in blood
A. 70-90 mg/dl
2. Balance accomplished by integration of glucose metabolic activity of liver, muscle and adipose tissue
What are the pancreatic hormones?
insulin and glucagon
What happens to glucose after a meal?
1. muscle storage for later use: glycogen
2. Energy for muscle and other tissue
3. Storage as fat (triglycerides)
4. Excretion in urine with high blood sugar
5. Energy for CNS
6. Liver storage for later use: glycogen
What is glycogenesis?
glucose -> glycogen
What is Glycogenolysis:
glycogen -> glucose
What is gluconeogenesis?
amino acids -> glucose
What is lipogenesis?
fatty acids & glycerol -> triglycerides
What is lipolysis?
triglycerides -> fatty acids & glycerol
What cells of the pancreas function as endocrine cells?
1. Pancreatic Islets
A. Alpha – glucagon
B. Beta – insulin
D. F cells
What is the function of the delta cells?
1. Secrete somastatin
What is the function of the F cells?
Secrete pancreatic polypeptide
What is the function of somastatin?
A. Inhibits glucagon, insulin & panc polypeptide secretion
B. Slows the rate of nutrient entry into cells
What is the function of glucagon?
1. Stimulates liver to break down glycogen
2. Increase blood glucose
3. Secreted during low blood glucose level
What is the function of insulin?
1. Decrease blood glucose
2. Secreted during high blood glucose level
3. Stimulates uptake of glucose by cells
4. Promotes muscle/adipose cells to take up glucose
5. Synthesis of glycogen in muscle/liver
6. Reduces lipolysis
What is the function of C peptide?
1. Connection between the A and B chains of the insulin structure. provides an index of beta cell function for pts who are receiving exogenous insulin. Half life of insulin is 5 mins; most is destroyed by proteases after glucose is transported.
2. provides an index of beta cell function for pts who are receiving exogenous insulin. Half life of insulin is 5 mins; x
3. Measured by RIA
Where is the highest concentration of insulin receptors?
1. Insulin receptors are present in almost all cell membranes
A. Highest concentration in liver, muscle, adipose tissue
What is the chain of events once insulin binds to the receptor proteins?
Stimulates a chain of events -> increase in number of glucose transport proteins in target cell membranes -> improved movement of glucose from plasma into cell cytosol
How does insulin affect the number of insulin receptors on cells?
Insulin increases the number of insulin? receptors
Where are GLUT-4 transporter proteins?
Muscle & fat cells contain a type of insulin-sensitive glucose transporter protein called GLUT-4
How does the binding of insulin affect the GLUT-4 transporters?
1. Normally, a few GLUT-4 transporters are in the cell membrane
2. Binding of insulin causes an recruitment of other GLUT-4 receptors from a cytoplasmic pool
How does exercise affect the GLUT-4 transporters?
Exercise promotes new GLUT-4 glucose transporters and their insertion into the cell membrane, increasing the muscle cell’s ability to take in glucose
What happens to the GLUT-4 receptors between meals?
Between meals, the recruited receptors return to ‘storage’ within the cell
How many forms of glucose transporters are present?
1. GLUTs (Glucose Transporter)- accomplish transport of glucose across a cell membrane
2. Six forms of GLUTs, but only GLUT-4 can respond to insulin
What is the function of GLUT 1?
GLUT-1 transports glucose across the blood-brain barrier
What is the function of GLUT 2?
GLUT-2 is involved with glucose transfer in the kidney
What is the function of GLUT 3?
GLUT-3 is the main transporter of glucose into neurons
What is the function of GLUT 4?
GLUT-4 transporters are most abundant in cells that represent the greatest use of glucose, namely muscle and fat cells
What is the action of insulin on glucose?
1. IncreasesGLUT4 transporters in membranes
A. Allows glucose entry into cells
2. Increase glycogen production from excess glucose
A. Facilitates storage of glucose
3. Inhibit glycogenolysis
A. Maintains glycogen storage
4. Inhibit gluconeogenesis
A. Prevents release of glucose back into blood
What is the action of insulin on lipids?
1. Inhibits lipase in adipose tissue
A. Decreases lipolysis
2. Inhibits oxidation of fatty acids
A. Decreases ketone formation
What is the action of insulin on protein?
1. Promotes active transport of amino acids from blood into muscle tissue
A. Decreases the circulating amino acid level
B. Provides building blocks for protein synthesis with cell
2. Increases rate of amino acid incorporation into protein
3. Inhibits protein degradation
What is the summary of insulin action?
1. Acts on skeletal muscle, liver, and adipose tissue
2. Stimulates pathways that lead to:
A. Increased glucose use
B. Increased carbohydrate and fat storage
C. Increased protein synthesis
3. Lowers blood glucose, fatty acid, and amino acid levels
How does elevated blood amino acid levels affect insulin levels?
stimulate beta cells to increase insulin secretion
How do GI hormones affect insulin levels?
GI hormones secreted in response to the presence of food stimulate insulin secretion
How does the parasympathetic NS affect insulin levels?
1. Occurs with food intake
2. Induces insulin secretion
How does the sympathetic NS affect insulin levels?
1. Inhibits insulin secretion
2. Blood glucose levels rise
What are the effects of insulin?
1. Increases glucose uptake and utilization by target cells
2. Stimulates glycogen formation in skeletal muscles and liver cells
3. Stimulates amino acid absorption & protein synthesis
4. Stimulates triglyceride formation in adipose tissue
What are the actions of glucagon?
1. Inhibit glycolysis
2. Increase gluconeogenesis
3. Increase glycogenolysis
4. Increase beta oxidation of FA’s
What is the pathophys of T1 DM?
1. Autoimmune destruction of insulin-producing cells
2. Circulating autoantibodies to:
A. Islet cells (ICA)
B. Insulin (IAA)
C. Glutamic acid decarboxylase (GAD65)
D. Tyrosine phosphatases (IA2 and IA2-beta)
E. Zinc transporters (ZnT8 / SLC30A8)
What are T1 DM pts at risk for?
What is the pathophys of T2 DM?
What are the risk factors for T2 DM?
Obesity, insulin insensitivity, dyslipidemia
What are the sxs of hypoglycemia when gluc < 54 mg/dl?
1. Autonomic NS stimulation sxs
What are the sxs of hypoglycemia when gluc < 50 mg/dl?
1. CNS sxs
What is diabetes insipidus?
Insufficiency of ADH secretion
What are the sxs of Diabetes insipidus?
1. Large volume of hypotonic urine is excreted
A. Trauma, disease or surgery affecting post pituitary or hypothalmus
B. Reduction in ADH receptors
A. Defect or damage to thirst mechanism
What are the microvascular/macrovascular complications from T1 and T2 DM?
2. Cardiovascular disease -> MI
3. Cerebrovascular disease -> Stroke
4. Diabetic nephropathy
What glucose level is insulin secretion inhibited?
What glucose level is glucagon, epi, growth hormone secreted?
What glucose level is cortisol secreted and cognitive dysfunction appear?
What glucose level does lethargy occur?
What glucose level does coma occur?