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Flashcards

Acid Base balance

Hannah Tribe KBF1 Degree English 27 cards

Cards in this deck (27)

  1. 1Where do acids come from?Metabolism
  2. 2How is pH controlled? (3)Buffering systems, Respiratory system and the kidneys
  3. 3Name 3 buffering systems1. Bicarbonate
    2. Phosphate
    3. Proteins
  4. 4What is pK?The equilibrium constant, so at this pH the concentration of acid = concentration of base
  5. 5When is a substance a good buffer?1pH either side of its pK
  6. 6Which is theoretically a better buffer, bicarbonate or phosphate? Why?Phosphate, because its pK value is nearer to normal body pH
  7. 7So why is bicarbonate the most important one?As we can independently regulate its levels with our ventilation and our kidneys
  8. 8In which order do the pH control mechanisms work in the body?1. buffers
    2. Respiratory system
    3. Kidneys
  9. 9What is the Henderson-Hasselbach equation?pH = pK + log ([HCO3-]/[CO2])
  10. 10What does it show?How the pH is affected when concentrations of bicarbonate and CO2 change
  11. 11How do you convert pCO2 to [CO2]?multiply by 0.03
  12. 12How do the kidneys contribute to acid base balance?They can control the excretion of H+ and HCO3-, as well as reabsorbing the HPO4 2-.
  13. 13What occurs in the proximal convoluted tubule?HCO3- combines with H+ that has been excreted via the Na+/H+ antiporter (mainly) and the H+ ATPase pumps on the apical surface, to form H2CO3 within the lumen. Cabonic anydrase on the apical surface converts it to CO2 and H2O. The H2O remains in the tubule to be excreted, and the CO2 diffuses into the cell, where it combine with water again in the presence of carbonic anhydrase to form H2CO3 which dissociates. The H+ is excreted via mechanisms above, and HCO3- is reabsorbed via a N+/HCO3- symporter on the basolateral membrane.
  14. 14What occurs in the distal convoluted tubule and collecting duct?On the apical surface of the intercalated cells, H+ ATPase pumps are the dominant transporter, excreting H+ ions, which are buffered in the urine by HPO4 2-. Any HCO3- in the cells is reabsorbed on the basolateral surface by HCO3-/Cl- antiporters.
  15. 15Explain how the kidney is able to synthesise bicarbonate ions 'de novo'.The tubular epithelial cells are able to metabolise the amino acid glutamine to alpha ketoglutarate and ammonia. The alpha ketoglutarate can form H2CO3 which dissociates. The HCO3- can enter the ECF via the HCO3-/Na+ symporter on the basolateral surface. The H+ ions can combine with the ammonia to form NH4+, which can be excreted via NH4+/Na+ antiporters on the apical surface, to be excreted as ammonium salts.
  16. 16Where are chemoreceptors located? (3)1. Medulla of brain
    2. Aortic arch
    3. Carotid bodies
  17. 17How is the respiratory system involved in acidosis/alkalosis?Chemoreceptors detect a fall in plasma pH and CSF pH and stimulate increased ventilation to try and lower CO2 levels and increase pH.
  18. 18How is the pH of the CSF altered?CO2 can diffuse across the blood-brain barrier, whereas charged molecules cannot. Once CO2 is across, it can lower the pH of the CSF.
  19. 19Where is there a high concentration of carbonic anhydrase?In RBCs
  20. 20What buffering occurs in RBCs?CO2 combines with H2O (with carbonic anhydrase) to form H2CO3, which dissociates. The H+ is buffered by Hb in the RBCs.
  21. 21What happens to the HCO3- formed here?It is transported out of the cell, in exchange for Cl- entering, to maintain the charge.
  22. 22What characterises metabolic acidosis?High ECF [H+] or low ECF [HCO3-]
  23. 23What causes metabolic acidosis? (3)1. Severe sepsis (produces lactic acid)
    2. Uncontrolled diabetes (diabetic ketoacidosis)
    3. Diarrhoea (loss of HCO3-)
  24. 24What are the compensation mechanisms for this? (3)1. Buffering system (= low HCO3-)
    2. Respiratory system (increase ventilation)
    3. Kidneys (increase excretion of H+, rebsorption of HCO3- and synthesis of HCO3- de novo [with increased NH4+ excretion])
  25. 25What is characteristic of metabolic alkalosis?Increased ECF [H+] or decreased ECF [HCO3-]
  26. 26What causes metabolic alkalosis?1. Vomiting (loss of [H+])
    2. Excessive thiazide diuretic use (loss of electrolytes increases loss of H+)
    3. Excessive antacid use
  27. 27What are the compensation mechanisms for this?1. Decreased ventilation in order to try and retain more CO2
    2. Buffering
    3. Kidneys (decreased H+ excretion, decreased HCO3- reabsorption and formation, increased HCO3- excretion)

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Degree KBF1 Flashcards on Acid Base balance, created by Hannah Tribe on 31/05/2014.
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Hannah Tribe
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