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15 Cards in this Set
- Front
- Back
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Where is most HCO3 reabsorbed? How is it reabsorbed?
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Proximal tubule
Moves across the tubular lumen by converting to H2O and CO2 via carabonic anhydrase, which diffuses across the lumen. It is then converted back by carbonic anhydrase to H2CO3. The H2CO3 dissolves into HCo3- and H+. The H+ is pumped back to the lumen and HCO3- is pumped out to the capillary with a sodium symporter. |
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How is HCO3- reabsorbed in the collecting duct alpha intercalated cell?
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HCO3- is converted by H2CO3 and converted into CO2 and H2O without carbonic anhydrase. These diffuse across the membrane and are converted backto H2CO3 with CA, which dissociates into H+ and HCO3-. H+ is transported back via a H+ ATPase and HCO3- is converted to the capillary by a Cl- antiporter.
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How is HCO3- secreted into the urine via the collecting duct beta intercalated cells? When is this mechanism used?
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CO2 and H2O are converted to H2CO3. This dissociates into HCo3- and H+ H+ is transported into the ccapillary via a H+ ATPase and HCO3- is transported into the lumen via a Cl- antiporter.
Only used during alkalosis. |
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Through what mechanism is HCO3- created in the nephron? What molecule is used?
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Titratable acid excretion.
Uses HPO4-. |
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How does titration create new HCO3- in the collecting duct and proximal tubule?
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Creation of HCO3- from CO2 and H2O within the cell causes an H+ to be excreted. H+ is taken up by HPO4 to neutralize.
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Through what mechanisms is ammonium secreted?
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In the proximal tubule, NH3 combines with H+ to form NH4+ which is exchagned for Na+ into the urine
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Through what mechanis is ammonium reabsorbed?
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In the thick ascending limb, NH4+ and Na+ are exchanged for 2 Cl-. It also enters via a specific NH4+ port. It dissociates into NH3 and H+ and the ammonia can diffuse into the interstitium.
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What are the functions of NH3 in the interstitium of the nephron?
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Diffuse back into the proximal tubule
Diffuse into the collecting duct Combine with H+ to form NH4+ to be excreted as urea |
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What mechanism causes the excretion of NH4+?
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Secretion in the collecting duct.
NH3+ diffuses into the collecting duct and reacts with H+. NH4+ is then trapped in the duct and excreted. |
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What is the most important mechanism for excreting H+? How much is excreted this way?
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Ammonium excretino
30-40 meq/L |
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What regulatory mechanisms act to increase H+ excretion?
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Decreased cell pH
Increased cell PCO2 Sodium reabsorption Plasma hypokalemia Aldosterone |
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What are the renal responses to metabolic acidosis?
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Reabsorption of filtered HCo3-
Increased urinary H+ excretion via increased NH4+ production and increasedH+ secretion. Increased HCO3- generation. |
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what are renal responses to metabolic alkalosis?
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Decreased reabsorption of HCO3-.
Increased HCO3- excretion. Decreased urinary H+ excretion Decreased HCo3- generation |
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What are renal responses to respiratory acidosis?
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Increased reabsorption of filtered HCO3-.
Dramatically increased urinary H+ excretion. Dramatically increased HCo3- generation. |
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What are renal responses to respiratory alkalosis?
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Decreased reabsorption and increased excretion of HCO3-.
Dramatic decrease in urinary H+ excretion. Decreased HCO3- generation. |
