Acid Base Balance Flashcards
Define pH
pH = -log10[H+]
How is pH buffered in the circulation?
H+ + HCO3-
to H2CO3
to H2O + CO2
What is the Henderson-Hasselbach equation?
pH = pK + log10 [base]/[acid]
What is the Henderson Hasselbach equation in relation to HCO3-?
pH = pK + log10[HCO3-]/0.22xPco2
Where Pco2 is the partial pressure of CO2
When is H+ produced?
ATP hydrolysis
During anaerobic respiration with the production of lactate
During the production of ketones
During ingestion of acids
How is HCO3- absorbed in the proximal tubule?
Carbonic anhydrase in the filtrate converts it to water and CO2
Carbonic anhydrase then converts it back to HCO3-
How is HCO3- excreted from the proximal tubule?
Via Na+ cotransporters
What is reabsorption of HCO3- dependent on?
Na+/H+ exchanger to maintain H+ concentration in the tubule
What promotes de novo HCO3- production?
CO2 from the vasa recta
How much HCO3- is reabsorbed?
At rest, almost all
An excess will not be reabsorbed
Where is H+ secreted in the nephron?
In the distal tubule
How is H+ secreted in the distal tubule?
H+K+ATPase
H+ATPase
How is free concentration of H+ in urine kept low?
Phosphate buffer
H+ HPO42- to H2PO4-
Where is ammonia secreted in the nephron?
Ammonium ion is produced in the proximal tubule by conversion of glutamine to glutamic acid and alpha ketoglutarate
NH4+ in the filtrate lumen as a reservoir for H+
How does pH vary across the nephron?
Falls
What is respiratory acidosis?
Caused by hypoventilation
CO2 goes up to decrease pH
Kidney increases the production of HCO3-
What is respiratory alkalosis?
Caused by hyperventilation and high altitude
pH decreases with a fall in CO2
Kidney decreases the production of HCO3-
What is metabolic acidosis?
Caused by renal failure, lactic acidosis, ketoacidosis, poisoning
H+ concentration increases and pH falls
CNS increases ventilation rate
What is metabolic alkalosis?
Caused by vomiting or contraction alkalosis
CNS decrease the ventilation rate
What is the anion gap?
The difference between positive and negative ions in the body
How is the anion gap measured?
[Na+]-[Cl-]-[HCO3-]
What is a normal anion gap?
3-11 mmol/l
What would be a cause of an increased anion gap?
Lactate
Ketones
Sulfates
Aspirin overdose
