Homeostasis

• What is homeostasis?

  The maintenance of a constant internal environment
• What are the four conditions needed for homeostasis?

  Blood sugar level, body temperature, water potential, pH level
• Why do we need to maintain pH and temperature?

  Changes reduce enzyme activity or may denature them
• Why is it important to maintain water potential and glucose levels in blood?

  High blood glucose decreases water potential, causing cell bursting
• What is negative feedback?

  A mechanism that restores levels back to normal
• Describe the process of negative feedback.

  Change detected, coordination center sends instructions, effector responds
• What is positive feedback?

  Deviation from optimum causes greater deviation
• What is glycogenesis?

  Conversion of glucose to glycogen
• What is glycogenolysis?

  Breakdown of glycogen to glucose
• What is gluconeogenesis?

  Production of glucose from glycerol/amino acids
• What happens when blood glucose concentration rises?

  Pancreas secretes insulin, glucose moves into cells
• What are the characteristics of hormones?

  Produced in glands, secreted into blood, long-lasting effects
• What are glucagon and insulin?

  Hormones involved in blood glucose regulation
• Which part of the pancreas secretes glucagon and insulin?

  Islets of Langerhans
• What is the effect of glucagon?

  Increases blood glucose levels
• What is the effect of insulin?

  Decreases blood glucose levels
• Where do glucagon and insulin bind?

  Glucagon binds to liver cells, insulin to liver and muscle cells
• What are the effects of glucagon secretion?

  Activates glycogen breakdown, less glucose uptake
• What are the effects of insulin secretion?

  Increases glucose absorption, converts glucose to fats
• How does insulin produce its effects?

  Insulin binds to receptors, increases glucose transporters
• What is the second messenger model?

  Mechanism of adrenaline and glucagon in glucose regulation
• Outline the second messenger model of hormone action.

  Hormone binds, activates adenyl cyclase, produces cAMP
• What is the glucose transporter in skeletal and cardiac muscle cells?

  Channel protein called GLUT4
• What causes type 1 diabetes?

  Genetics, infection of the pancreas
• What causes type 2 diabetes?

  Obesity, poor diet
• Who does type 1 diabetes affect?

  Begins in childhood
• Who does type 2 diabetes affect?

  Affects older people, over 40
• What goes wrong in type 1 diabetes?

  Insulin is not produced
• What goes wrong in type 2 diabetes?

  Insulin produced but body doesn’t respond
• What treatments exist for type 1 diabetes?

  Insulin injections
• What treatments exist for type 2 diabetes?

  Exercise, healthy diet, medications
• What are the structures of the kidney?

  Fibrous capsule, cortex, medulla, renal pelvis, ureter, renal artery, renal vein
• What are the structures of the nephron?

  Renal/Bowman's capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule, collecting duct
• What blood vessels are associated with each nephron?

  Afferent arteriole, glomerulus, efferent arteriole, blood capillaries
• What does the kidney do?

  Filters the blood and produces urine
• Why is the efferent arteriole narrower than the afferent arteriole?

  To increase pressure in the glomerulus
• What is formed by ultrafiltration?

  Glomerular filtrate
• What substances undergo ultrafiltration?

  Water, glucose, amino acids, vitamins, drugs, urea
• What are the three layers of the filter between the glomerulus and nephron?

  Endothelium, basement membrane, epithelium of renal capsule
• What are the properties of the endothelium of blood capillaries in ultrafiltration?

  One cell thick, perforated with pores