Physio L33 Renal Control- Secretion- Filtrate

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  1. Renin- Angiotensin System
    • Maintain BP by increasing Na+ and water reabsorption
    • Decrease renal BP -> release of renin from kidney JG cells
    • Renin is a protease
  2. Production of Angiotensin II
    • Renin converts angiotensinogen into angiotensin I
    • Angiotensin converting enzyme (ACE) converts A-I to A-II
    • ACE is in the walls of lung capillarries
  3. Effects of Ang II
    • Powerful vasoconstrictor-> increases BP
    • Causes release of aldosterone from adrenal cortex
  4. ACE Inhibitors
    • Block production of Ang II
    • Used as treatment for hypertension
    • Few side effects, but may produce fetal development problems
    • (used for elevated BP)
  5. Tubular Secretion
    • Extra removal from plasma
    • Carriers and pumps move material from tubular cells into filtrate
    • Most secretion is at proximal tubule
    • Organic acids and bases secreted: poisons, medicines, dyes, food additives
  6. Renal Blood Flow- PAH
    • PAH is totally secreted from plasma
    • Appearance in urine proportional to renal blood flow
    • RBF: ~20-25% of cardiac output
  7. H+ Secretion
    • Carbonic anhydrase in tubular cells make H+ and HCO3-
    • H+ secreted in both proximal and distal tubules
    • Uses Na+ - H+ countertransport, H+ into filtrate HCO3-, -> ISF, net loss of H+
  8. K+ Secretion
    • K+ reabsorbed in exchange for Na+ in proximal tubule
    • The Na+ pump activity increases tubular cell K+, which increases it's secretion by the proximal tubule cells
    • Since K+ and H+ both exchange with Na+, an increase in the secretion of one decreases secretion of the other
  9. Plasma Clearance
    • Measure of the kidney's ability to remove a substance from the plasma
    • It is the volume of plasma from which an amount of material has been removed
    • Glucose has zero clearance
    • If a substance is filtered but not secreted or reabsorbed, like inulin, its plasma clearance is the GFR
    • If a substance is both filtered and secreted, its clearance is greater than GFR (penicillin)
    • If a substance, like PAH, is filtered and entirely secreted, its plasma clearance is the renal blood flow ~20-25% of cardiac output
    • GFR/ RBF= C-inulin/ C=PAH= Filtration Fraction ~20%
  10. Loop of Henle
    • Creates osmotic gradient in kidney medulla
    • 300 mOsm at cortex, 1200mOsm in deep medulla
    • Filtrate at the end of the Loop of Henle is 100 mOsm
    • Plasma is 300 mOsm
  11. Countercurrent Multiplication
    • Descending limb of the Loop of Henle is H2O permeable
    • Ascending limb is H2O impermeable- H+. K+. Cl- pumped out
    • Filtrate entering distal tubule always dilute, ~100Osm (never changes)
  12. Vasopressin present
    distal and collecting tubule permeable to water
  13. Glomerulus -> Bowman's Capsule (cortex)-> Proximal tubule (cortex)-> Loop of Henle (medulla)-> Distal Tubule (cortex)-> Collecting Tubule (medulla)

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Physio L33 Renal Control- Secretion- Filtrate
2013-11-26 01:07:47

msu physio
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