Chapter 78: Insulin, glucagon, and diabetes (Discussion 9)

Question 1

Pancreas cells and secretions

Answer 1

From Islets of Langerhans

• Alpha cells (~60%): glucagon
• Beta cells (~25%): insulin and amylin (inhibits insulin)
• Delta cells (~10%): somatostatin - inhibit glucagon and insulin secretion

Question 2

Insulin and Mechanism

Answer 2

Stimulated by: increase blood glucose

Stimulates: increase cell uptake of glucose (binds receptors, not a transporter)

• ↑ glucose metabolism energy
• ↑ protein/lipid synthesis
• ↑ energy storage
  
  • glycogen in muscles (for exercise)
  • glycogen in liver (released between meals)
  • fat in adipose tissue
• leads to ↓ blood glucose
• not required for uptake of glucose by brain (dependent on glucose metabolism)

Secretion mechanism:

• glucose into beta cell –> ATPS –> closing of gated K+ channels –> depolarization –> influx of Ca2+ –> release insulin-containing vesicles

Question 3

Glucagon

Answer 3

Stimulated by: ↓ blood glucose

Stimulates: ↑ blood glucose (opposite of insulin)

• ↑ glycogenolysis: breakdown of glycogen in liver
• ↑ gluconeogenesis in liver
• ↑ fat metabolism for energy

Question 4

Consequences of hyperglycemia

Answer 4

• ↑ECF osmolarity –> Cellular dehydration
• ↑ Renal fluid osmolarity –> glucose loss in urine
• ↑ Renal fluid osmolarity –> H2O + electrolyte loss in urine
• ↑ plasma glucose –> damage to blood vessels –> stroke, MI, Renal disease, etc…

Question 5

Type I Diabetes

Answer 5

Insulin-Dependent Diabetes: lack of insulin secretion

Caused by: auto-immune or viral destruction of beta cells (hereditary involvement)

Treatment: insulin injections

Question 6

Type II Diabetes

Answer 6

Non-insulin dependent diabetes: resistance to effects of insulin

Caused by: obesity (hereditary involvement)

Treatment:

• Early stages: manage/reverse with diet, exercise and some drugs
• Later stages: insulin injections

Question 7

Resulting effects of diabetes from chronically high glucose

Answer 7

• Polyuria –> dehydration + increased thirst
• Poor blood flow –> peripheral tissue death/neuropathy
• Renal disease/failure (will eventually need dialysis)
• Hypertension, atherosclerosis, MI
• ↑ Fat metabolism utilization –> ketoacidosis (metabolic acidosis) –> can lead to coma
• Diabetic retinopathy

Question 8

Insulin shock

Answer 8

Caused by hypoglycemia from over-administering insulin

Treat with IV/oral glucose