Lecture 03, 4

• How are glucose, bicarbonate ions, sodium ions, and water reabsorbed in the nephron?

  By active and passive processes

  
• Where does tubular reabsorption and secretion occur in the nephron?

  In various locations of the nephron

  
• Compare and contrast tubular reabsorption and secretion.

  • Energy required: Reabsorption uses energy, secretion may not
  • Solute movement: Reabsorption moves solutes into blood, secretion moves solutes into urine
  • Concentration gradients: Reabsorption often against gradients, secretion often with gradients
• What is the role of aldosterone in reabsorption and secretion?

  It promotes sodium reabsorption and potassium secretion

  
• What does antidiuretic hormone (ADH) do in the nephron?

  It increases water reabsorption in collecting ducts

  
• What is the function of atrial natriuretic peptide (ANP) in the nephron?

  It decreases sodium and water reabsorption

  
• What is the paracellular pathway in tubular reabsorption and secretion?

  • Pathway outside of cells
  • Occurs in spaces between cells
  • Regulated by tight junctions
• What is the transcellular pathway in tubular reabsorption and secretion?

  • Movement across a cell
  • Passes through cell membrane
  • Involves cytoplasm

  
• What are the types of membrane transport involved in renal physiology?

  Facilitated diffusion, primary and secondary active transport

  
• What percentage of energy used by kidneys is spent on sodium reabsorption?

  80%
• What substances are secreted in the proximal tubule?

  1. Hydrogen ions
  2. Nitrogenous waste products
  3. Drugs (penicillin, morphine)
  4. Uric acid
  5. Ammonium ions
  6. Creatinine
  7. Urea

  
• What is the permeability of the ascending limb of the Loop of Henle?

  It is impermeable to water

  
• What is the permeability of the descending limb of the Loop of Henle?

  It is permeable to water

  
• How does aldosterone function in the kidneys?

  • Targets principal cells in collecting ducts
  • Involved in sodium reabsorption
  • Involved in potassium secretion
  • Responds to hormones like ADH

  
• How does anti-diuretic hormone (ADH) affect the collecting ducts?

  It increases their permeability to water

  
• What is diabetes insipidus?

  Condition where kidneys stop conserving water
• What are the symptoms of diabetes insipidus?

  Thirst and dehydration
• What causes diabetes insipidus?

  Damage to hypothalamus or low ADH
• How does the counter current multiplier establish the medullary osmotic gradient?

  • Involves the Loop of Henle
  • Creates a gradient through differential permeability
  • Enhances concentration of urine

  
• How does the permeability of renal tube sections affect urine concentration?

  It leads to either dilute or concentrated urine

  
• What roles do the Loop of Henle, vasa recta, and counter current mechanism play in urine concentration?

  • Loop of Henle: establishes osmotic gradient
  • Vasa recta: maintains gradient
  • Counter current mechanism: enhances concentration

  
• What renal adaptations do desert-dwelling animals have to conserve water?

  • Produce highly concentrated urine
  • Have long loops of Henle
  • Juxtamedullary nephrons
  • Thicker medulla in smaller rodents
• How do the Loop of Henle adaptations differ in desert-dwelling animals compared to humans?

  • Desert animals have longer loops of Henle
  • Most are juxtamedullary type
  • Humans have 15% juxtamedullary nephrons