Renal Physiology 5

  1. Which section of the nephron is known as the "workhorse?"
    The proximal tubule.
  2. The proximal tubule reabsorbs ______ % of filtered fluid and NaCl.
  3. True or False?
    The proximal tubule of the nephron is the site of secretion of organic acids and bases.
  4. True or False?
    The proximal tubule of the nephron reabsorbs about 80% of filtered glucose and amino acids.
    • False.
    • 100% is reabsorbed.
  5. The osmolarity of the solution inside the proximal tubule is ___________, compared to the osmolarity of the solution in the interstitium.
    Isosmotic. 300 mosmol.
  6. Explain why the processes that occur in the proximal tubule are known as "bulk reabsorption."
    Because H2O follows the solutes as they are transported out.
  7. The thin descending loop of Henle is mostly permeable to what? How is it transported?
    • Water.
    • Passive diffusion into the hyperosmotic medullary interstitium.
  8. The thick ascending loop of Henle is permeable to what? Impermeable to what? How is it transported?
    • Permeable to Na+, K+, and Cl-, by active transport.
    • Impermeable to water.
  9. As fluid passes through the thin descending loop of Henle, its osmolarity (increases / decreases).
  10. As fluid passes through the thick ascending loop of Henle, its osmolarity (increases / decreases).
  11. Describe the absorption characteristics of the early distal tubule.
    Similar to the thick ascending loop of Henle (except there is no K+ reabsorption).
  12. Describe the absorption characteristics of the late distal tubule.
    • Similar to those of the cortical collecting duct.
    • Site for hormone action.
  13. True or False?
    ADH acts all the way down the collecting duct, but Aldosterone only acts at the cortical collecting duct.
  14. What is the result of ADH action along the collecting duct of the nephron?
    ADH results in increased water reabsorption along the collecting duct and therefore a decrease in urine output.
  15. What is the physiological mechanism by which ADH increases H2O reabsorption?
    When ADH binds to tubular epithelial cells of the LDT and collecting duct, aquaporons are placed on the apical surfaces of the epith. membranes.
  16. When aquaporons are placed on the tubule epithelial cells, how does water move through the cells and into the interstitium?
    The very large solute concentration of the renal medulla's interstitium causes water to flow out of the tubule by passive diffusion.
  17. What points along the nephron are permeable to water?
    • 1.) Proximal tubule
    • 2.) Thin descending loop of Henle
    • 3.) Late distal tubule (ADH)
    • 4.) Collecting duct (ADH)
  18. What points along the nephron are impermeable to water?
    • 1.) Thin ascending loop of Henle
    • 2.) Thick ascending loop of Henle
    • 3.) Early distal tubule
    • 4.) Late distal tubule (no ADH)
    • 5.) Collecting duct (no ADH)
  19. Which portions of the nephron are under hormonal control? Which hormones?
    • 1.) Late distal tubule - ADH and aldosterone
    • 2.) Cortical collecting duct - ADH and aldosterone
    • 3.) Medullary collecting duct - ADH
    • 4.) Papillary collecting duct - ADH
  20. Renal function will be most affected if which portion of the nephron is disturbed?
    The proximal tubule.
  21. Under normal circumstances, the strongest starling force in the peritubular capillaries is _________, and favors net ___________.
    • 1.) Colloid osmotic pressure IIpc
    • 2.) Absorption (negative NFP)
  22. True or False?
    An increase in MAP will cause an increase in the hydrostatic pressure of the peritubular capillaries.
  23. List, in order, the process by which an increased MAP results in an increased Ppt.
    • 1.) Increased MAP
    • 2.) Constriction of afferent arteriole (to stabilize GFR)
    • 3.) Dilation of efferent arteriole (to stabilize GFR)
    • 4.) Increased Ppt
  24. How does increased hydrostatic pressure in the peritubular capillaries help to lower MAP
    Increased Ppt results in less reasborption and therefore an increase in urine output, thus slightly depleting the body's fluid volume and lowering MAP.
  25. The afferent arteriole more significantly affects (urine output / GFR), while the efferent arteriole more significantly affects (urine output / GFR).*
    • 1.) GFR
    • 2.) Urine output
  26. True or False?
    When MAP changes, the afferent arteriole will keep both GFR and Ppt relatively constant.
    • False.
    • GFR will remain constant, but Ppt will be affected depending on the actions of both the afferent and efferent arterioles.
  27. What is the formula for filtration fraction?
    Filtration fractions = GFR / Renal Plasma Flow
  28. True or False?
    Changes in filtration fraction help predict changes in IIgc.
    • False.
    • Filtration fraction helps predict changes in IIpt.
  29. What disease state consists of a tumor(s) that produces proteins, thus raising [protein]plasma and therefore decreasing GFR?
    Multiple myeloma.
  30. What disease state decreases the liver's ability to synthesize proteins, thus lowering [protein]plasma and therefore increasing GFR?
Card Set
Renal Physiology 5
Renal Physiology 5