Anatomy/Phys Diabetes - Endo Flashcards
Terminology
Carbohydrate Metabolism
- Glycolysis- breakdown of glucose
- Glycogenesis- synthesis of glycogen
- Glycogenolysis—breakdown of glycogen to glucose
- Gluconeogenesis—synthesis of glucose from amino acid, lactic acid and glycerol 3-phosphate
Fat Metabolism
- Lipolysis – break down of triglyceride
- Lipogenesis- synthesis of triglyceride
Structure of Pancreas
- Has both exocrine and endocrine cells
- Acinar cells (exocrine) produce an enzyme-rich juice for digestion
Pancreatic islets (islets of Langerhans) contain endocrine cells
- Alpha cells secrete glucagon (a hyperglycemic hormone)
- Beta cells synthesize preproinsulin, which in turn, splits into insulin(a hypoglycemic hormone) and C peptide*
- Delta (δ) cells secrete somatostatin (inhibits release of both glucagon and insulin)
- PP cells secrete pancreatic polypeptide hormone (stimulates secretion of gastric and intestinal enzymes and inhibits intestinal motility
Action of Insulin
- The main action of Insulin is it promotes the utilization of carbohydrates for energy, whereas it depresses the utilization of fats.
1. Effects of insulin on Carbohydrate metabolism: -Lowers blood glucose levels - Enhances membrane transport of glucose into adipose tissue and resting skeletal muscle cells (glucose can enter working muscle without the aid of insulin)
- Increases glucose use by tissue by metabolizing it to CO2 & H2O
- Enhances glycogenesis in muscles
- Promotes liver uptake, storage, and use of glucose
- Inhibits glycogenolysis and gluconeogenesis
- Effects of Insulin on Protein Metabolism: Promotes protein synthesis and storage
- Increases amino acid uptake by muscle cells(similar to Growth hormone*)
- Decreases protein breakdown (deficiency of insulin results in a breakdown of protein)
- Depresses the rate of gluconeogenesis - Effects of Insulin on Fat Metabolism
- Increases triglyceride synthesis(lipogenesis) in adipose tissue
- Increases triglyceride uptake by fat cells
- Decreases triglyceride breakdown (lipolysis) in adipose tissue, by decreasing the activity of hormone-sensitive lipase - Effects on Potassium
- Insulin pumps K+ into cells (by increasing the activity of Na/K-ATPase in most body tissues)
- This K+ lowering action of insulin is used to treat acute, life threatening hyperkalemia
Control of Insulin Secretion
Stimuli that inhibit insulin secretion
- decreased blood glucose
- fasting
- somatostatin and leptin
- sympathetic innervation: norepinephrine
Stimuli that promotes insulin secretion
- increased blood glucose, free fatty acids, amino acids
- GIT hormone, GIP, gastrin, secretin, CCK, glucagon, GH, cortisol
- Parasympathetic stimulation
- Beta adrenergic stimulation
- sulfonylurea drugs (glyburide, tolbutamine)
Effects of Hyperglycemia
Vascular pathology:
Atherosclerosis
Peripheral vascular disease
- atrophy of skin and loss of hair of lower extremity
- claudication
- nonhealing ulcers
- gangrene of lower extremities
Microvascular disease
- diffuse thickening of basement membranes
- hyaline arteriosclerosis
Diabetic nephropathy:
-renal artery atherosclerosis
- hyaline arteriosclerosis of afferent and efferent arterioles
- diffuse glomerulosclerosis
- nodular glomerulosclerosis
- pyelonephritis
- renal failure
Diabetic retinopathy:
- microaneurysms-nonproliferative phase
- retinal hemorrhages and exudates-proliferative phase
- neovascularization
- increased rate of cataracts and glaucoma
Glucagon-Action
Major target is the liver, where it promotes
- Glycogenolysis
- Gluconeogenesis
- Release of glucose to the blood
- Increases liver ketogenesis and decreases lipogenesis
- Increases ureagenesis
- Increases lipolysis
- Increases insulin secretion
Control of Glucagon Secretion
Stimuli that inhibit glucagon secretion
- hyperglycemia
- insulin
- somatostatin
stimuli that promote glucagon secretion
- hypoglycemia
- amino acids
