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BMS11-1038 Kidney Function IV: Regulation of Acid Base status

Evian Chai BMS11 - Renal System English 25 cards

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  1. 1Where are the three locations of renal acid/base handling?1. Proximal convoluted tubule
    2. Ascending loop of henle
    3. Cortical collecting ducts at intercalated cell type A
  2. 2When does H+ excretion occur?When there is no bicarbonate in the tubular lumen, H+ will combine with a non-bicarbonate buffer and be excreted
  3. 3What is the pH determining acidosis/alkalosis?7.35
  4. 4What is the bicarbonate buffer system?CO2+H20<->H2CO3<->HCO3-+H+
  5. 5What is respiratory acidosis caused by?Insufficient CO2 excretion by lungs aka hypoventilation
  6. 6What is metabolic acidosis caused by?Fall in plasma HCO3- due to:
    1. True HCO3- deficet (renal tubular acidosis/diarrhea)
    2. H+ gain from exogenous acid, abnormal carb/lipid/protein metabolism
  7. 7What causes respiratory alkalosis?Fall in pCO2 due to:
    1. Excess central respiratory drive (from aspirin overdose/fever)
    2. Hypoxic stimulation (altitude increase, hyperventilation, pulmnary embolism)
  8. 8What causes metabolic alkalosis? pH>7.45Increased plasma bicarbonate due to:
    1. Loss of gastric acid from vomiting
    2. Excess aldosterone (increases H+ ATPase)
    3. Excess alkali ingestion
  9. 9What causes acute respiratory acidosis?1. Airway obstruction eg. asthma
    2. Drug induced eg. narcotics
  10. 10What are the three sources of acid loss?1. Utilisation of H+ to metabolise organic anions
    2. Vomit/urine
    3. Hyperventilation
  11. 11What are the 3 sources of acid gain?1. Metabolic acid production from proteins etc.
    2. H+ intake from CO2
    3. Loss of bicarbonate in urine/diarrhea
  12. 12What 3 types of airway obstriction cause CHRONIC respiratory acidosis?1. Lung damage (fibrosis)
    2. Chest wall disorders
    3. Neuromuscular disorders like lateral scelerosis
  13. 13pH= pK+ log[(...)/(...) CB WA1. HCO3- (CB)
    2. H2CO3 OR PCO2
  14. 14Normal Values Body pH= ... Parterial CO2: ... Aterial/venous [HCO3-]= ... Aterial pH= ...1. pH=7.35-7.45
    2. Parterial CO2=4-6kPa
    3. 25nM
    4. arterial pH=7.5
  15. 15How does the respiratory brain stem respond to metabolic acidosis?Increase ventilation to decrease pCO2, increasing pH
  16. 16How does glutamine metabolism add new HCO3 to the plasma?1. Glutamine (filtered) enters tubular epithelial cell
    2. Glutamine breaks down into NH4+ + HCO3-
    3. HCO3- reabsorbed into interstitial fluid
    4. NH4+ goes to tubular lumen via Na+NH4+ cotransporter and is excreted
  17. 17How does filtered HCO3 in the filtrate get reabsorbed?1. In the tubular lumen, it combines with H+ to form H2CO3
    2. H2CO3--> CO2+H20, enters tubule epithelial cell
    3. Reabsorbed (see next slide)
  18. 18How does bicarbonate reabsorption occur in the tubular epithelial cell?1. H20+CO3 combines into H2CO3 via enzyme carbonic anhydrase
    2. H2CO3-->H+ + HCO3-
    3. HCO3- reabsorbed via HCO3/Na+ cotransporter
    4. H+ goes to tubular lumen via H+/Na+ exchanger
  19. 19How do the following respond to respiratory alkalosis? 1. Chemical buffers 2. Respiratory brain stem 3. Renal mechanisms1. As CO2 concentration falls, plasma HCO3 combines with H+ to form H20+CO2. So, concentration of HCO3-/H+ drops
    2. Lower ventilation if possible
    3. Lower H+ secretion in tubules, so less to combine with HCO3- for reabsorption (so less HCO3- in plasma). Produces alkaline urine
  20. 20How do the following respond to respiratory acidosis: 1. Chemical buffers 2. Brainstem respiratory centre 3. Renal mechanisms1. As more CO2 is present, more HCO3- + H+ is produced via bicarbonate buffer system
    2. Cannot be adjusted as ventilation is issue
    3. Increase HCO3- reabsorption to increase secretion/excretion of H+
    Increase glutamine metabolism to increase HCO3 in plasma
    Produces acidic urine
  21. 21How do the following respond to metabolic alkalosis: 1. Chemical buffers 2. Respiratory brainstem 3. Renal mechanisms1. Fall in H+ pushes rxn left, generating more HCO3- and H+, and decreasing CO2
    2. Respiration slows (hypoventilation) to retain more CO2 to make HCO3-/H+
    3. Excess bicarbonate excreted
  22. 22How do renal mechanisms respond to metabolic acidosis?1. Increase H+ secretion
    2. Increase glutamine metabolism
    Both these raise plasma HCO3 to a normal level
  23. 23How do chemical buffers respond to metabolic acidosis?1. Rise in H+ will cause HCO3- to drop as it combines to form CO2. pCO2 will rise
  24. 24Chemical buffers work in {{c1::seconds}} eg. ... in ECF,...in ICF, ...in urine Brain respiratory center works in {{c5::minutes}} in response to changes in arterial changes Works by...to expel/retain CO2 Renal mechanisms work in ... For each H+ secreted, HCO3- is added to blood1. Seconds
    2. Bicarbonate, phosphate, phosphate/ammonia
    1. Minutes
    2. pCO2/pO2
    3. Adjusting ventilation
    1. Hours to days
  25. 25—

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BMS11 - Renal System Flashcards on BMS11-1038 Kidney Function IV: Regulation of Acid Base status, created by Evian Chai on 28/04/2020.
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