Renal Physiology 6

  1. Define pressure diuresis.
    Increased urine output in response to an increase in MAP.
  2. How is urine output increased in pressure diuresis?
    Ppt is ultimately increased, resulting in less reabsorption (a NFP that is less negative) in the proximal tubule and therefore more urine excretion.
  3. True or False?
    In pressure diuresis, reduced formation of angiotensin II also occurs.
  4. Define renal clearance.
    A volume of plasma completely "cleared" of a substance by the kidneys per unit time.
  5. How do you calculate renal clearance?
    • Clearance (mL/min) =
    • urine flow rate x [substance]urine / concentration in plasma
  6. Explain why inulin is a good way to determine GFR.
    • It is a polysaccharide that is small enough to be filtered, but is too large to be reabsorbed or secreted.
    • Therefore, all the inulin that is filtered is excreted.
    • Clearance = GFR.
  7. [inulin]plasma = 100 mg / 100 mL
    [inulin]urine = 125 mg/mL
    urine flow rate = 1 mL/min

    What is the renal clearance of inulin?
    125 mL/min.
  8. What does it mean if the clearance of drug X is greater than the clearance of inulin?
    Drug X was both filtered and secreted.
  9. What does it mean if the clearance of drug X equals the clearance of inulin?
    Drug X was only filtered.
  10. What does it mean if the clearance of drug X was less than the clearance on inulin?
    Drug X was filtered and reabsorbed.
  11. What is an example of an endogenous chemical who's clearance nearly resembles that of inulin?
  12. What is key concept # 4 in regards to the body's osmolarity?
    Osmolarity = [NaCl] / [H2O]
  13. True or False?
    KCl is the most significant source of osmotically active solute in the body.
    • False.
    • NaCl is the most significant source.
  14. How will an increase in body fluids without an increase in NaCl effect ECF osmolarity?
    Osmolarity will decrease --> the ECF will be hypo-osmotic.
  15. How will an increased amount of fluid excreted from the body without a similar increase in NaCl excretion affect ECF osmolarity?
    ECF osmolarity will increase --> hyper-osmotic.
  16. How will the kidneys correct a hypo-osmotic ECF?
    Excrete water in excess of solutes (dilute urine) (ADH absent).
  17. How will the kidneys correct a hyper-osmotic ECF?
    Excrete solutes in excess of water (concentrated urine) (ADH present).
  18. True or False?
    The kidneys can conserve water and solutes, but cannot create it once it is lost.
  19. What is the obligatory urine output?*
    The body must excrete a solute load of about 1200 mOsm / day.
  20. What is the maximum solute concentration the body can produce in urine? The minimum?
    • 1200 mOsm / L max.
    • 50 mOsm / L min.
  21. What are the characteristics of AHD?
    • 1.) Anti-diuretic hormone aka Vasopressin
    • 2.) Secreted by posterior pituitary gland
    • 3.) Controls water permeability of LDT, CCT, and collecting ducts.
  22. Isosmotic urine has an osmolarity of 300 mOsm, while dilute urine is ________ than 300, and concentrated urine is ________ than 300.
    • 1.) less than
    • 2.) greater than
  23. If ADH is not present at the latter portions of the nephron, (dilute / concentrated) urine will be excreted.
    Without ADH, water will not be reabsorbed, and dilute urine will be excreted.
  24. Which portion(s) of the nephron always produce dilute filtrate?
    • 1.) Thick ascending loop of Henle
    • 2.) Early distal tubule
  25. True or False?
    The renal medullary interstitium is very hyperosmotic.
  26. In what portion of the nephron are solutes actively transported out of the tubule?
    The thick ascending loop of Henle.
  27. How is the high osmolarity of the renal medullary interstitium maintained, even as water is reabsorbed?
    Countercurrent exchange with the vasa recta.
  28. Why is the high osmolarity of the renal medulla necessary for water reabsorption (when desired)?
    Water needs a concentration gradient to follow or no net movement will occur, despite the presence of aquaporons.
  29. How does ADH allow water to be reabsorbed from the tubule?
    ADH triggers aquaporon synthesis in tubular epithelial cells and causes the channels to be placed on the apical surface of the membrane.
  30. With high enough ADH levels, the osmolarity of the urine to be excreted will be the same as ___________.
    • The renal medulla.
    • The resulting permeability will allow water to equillibrate with the surrounding interstitium.
Card Set
Renal Physiology 6
Renal Physiology 6