Homeostasis(kidney)

• What are the two primary roles of the kidneys?

  Filter blood and produce urine
• Besides filtering blood, what else do kidneys control?

  Water potential of blood
• What is the functional unit of the kidney?

  Nephron
• Where does blood enter the glomerulus?

  Afferent arteriole
• Where does blood exit the glomerulus?

  Efferent arteriole
• What does the efferent arteriole branch into?

  A network of capillaries
• Why does the efferent arteriole branching into a network of capillaries around the nephron structure ensure?

  A short diffusion distance
• What are nephrons responsible for?

  Blood filtration and urine production
• Why are substances forced out of capillaries in the glomerulus?

  High hydrostatic pressure
• What causes the high hydrostatic pressure in the glomerulus?

  Efferent arteriole smaller diameter
• What is the process called where substances are forced out of the capillaries due to high hydrostatic pressure?

  Ultrafiltration
• What three structures must substances pass through to reach the Bowman's capsule during ultrafiltration?

  Endothelium, basement membrane, podocytes
• What is the mixture of substances that enters the Bowman's capsule called?

  Glomerular filtrate
• Where does selective reabsorption primarily occur in the nephron?

  Proximal convoluted tubule
• How are sodium ions transported from epithelial cells into the blood in the proximal convoluted tubule?

  Actively
• How are sodium ions transported back into epithelial cells from the blood?

  Facilitated diffusion and cotransport
• How is water transported back into the blood in the proximal convoluted tubule?

  Osmosis
• What are the adaptations of the proximal convoluted tubule?

  • Mitochondria for ATP production
  • Microvilli for increased surface area
  • Variety of co-transport molecules
  • Short diffusion distance
• What is the purpose of mitochondria in the proximal convoluted tubule?

  Produce ATP for active transport
• What is the function of microvilli in the proximal convoluted tubule?

  Increase surface area
• What is the significance of short diffusion distance in the proximal convoluted tubule?

  Increases rate of reabsorption
• In the loop of Henle, how does water move out of the descending limb?

  Via osmosis
• In the loop of Henle, how do sodium ions move out of the ascending limb?

  Via active transport
• Where do sodium ions move to from the ascending limb of the loop of Henle?

  Medulla
• What happens to the sodium ions that move into the medulla?

  Reabsorbed into blood
• What type of exchange is the movement of water and sodium ions in the loop of Henle?

  Countercurrent flow
• After the loop of Henle, where does the filtrate move next?

  Distal convoluted tubule
• Where does the filtrate go after passing through the distal convoluted tubule?

  Collecting duct
• What detects changes in the blood's water potential?

  Osmoreceptors in hypothalamus
• Where is ADH stored?

  Posterior pituitary gland
• What happens when blood water potential decreases?

  ADH release is stimulated
• How does ADH affect the distal convoluted tubule and collecting duct?

  Increases permeability to water
• What is the result of increased water reabsorption due to ADH?

  Increased blood water potential
• What type of urine is produced when ADH increases water reabsorption?

  Smaller volume of less concentrated urine
• What happens to ADH production once blood water potential returns to normal?

  Pituitary gland decreases production
• What happens when blood water potential increases?

  Less ADH is released
• How does less ADH affect the collecting duct and distal convoluted tubules?

  Permeability decreases
• What is the effect of reduced permeability on water potential of blood?

  Water potential to fall
• What type of urine is produced when less ADH is released?

  Larger volume of less concentrated urine
• What happens to ADH levels when the blood water potential returns to normal?

  More ADH is released