Acid-base regulation Flashcards
Physiological pH: recall the normal plasma pH and the limits compatible with life
Regulator (blood pH) is more important in distinguishing normality/abnormality in urine
Buffering: explain the bicarbonate buffer system, recall the normal value for plasma bicarbonate, recall and apply the Henderson-Hasselbach equation, and explain renal mechanisms to alter/maintain serum bicarbonate concentration (reabsorption and secretion)
Bicarbonate
- HIGH CAPACITY CHEMICAL BUFFER
- can respond rapidly to changes in
- METABOLIC ACID
- can be produced from VOLATILE RESPIRATORY ACID
Most bicarbonate is absorbed in Proximal Convoluted Tubule - 80%
Ascending limb reabsorb most of what is left - 10%
Distal convoluted tubule - 6%
Collecting duct 4%
Useful buffering mechanism – we want all of it reabsorbed
pH=pK+〖log〗_(10 ) ([〖HCO〗_3^-])/(〖[CO〗_2])
Davenport diagram
Horizontal line – normal bicarb
Vertical line – normal H+
PCO2- 5.4 kPa
- TOP RIGHT QUADRANT:
- Metabolic alkalosis
- pH will increase
- Bicarb increases
- Migration along the green line because pCO2 not necessarily changes
- metabolic acidosis
(less steep than alkalosis)
- acute respiratory alkalosis
- Chronic respiratory alkalosis
- Chronic respiratory acidosis
- Acute respiratory acidosis
Acute conditions go sideways because not much time is given to the body to accommodate change
Phosphate, ammonium and protons: explain the mechanisms involved in the excretion of phosphate, ammonium salts and hydrogen ions
1. Proximal convoluted tubule
- Carbonic anhydrase combines with bicarbonate -> co2 and H20
- C02 goes into the cell
- Inverse carbonic anhydrase enzyme remakes bicarbonate from CO2 and H2P
- Bicarbonate reabsorbed in capillaries by:
- Sodium bicarbonate cotransporter
- Chloride bicarbonate exchanger
(Cl- re-pumped outside of the cell and Na is removed through Na+K+ ATPase)
- ATPases pump the H+ outside the cell
- Bicarb is saved in the cell
2.
- Acid-secreting cell (alpha cell) (same mechanism with the one above)
- Bicarbonate-secreting cells (beta cell; same mechanism but exactly the opposite -> sends bicarbonate into filtrate and H into the interstitium
- significance: If we are trying to reduce H we increase bicarb which allows more bicarb and h to come together –> battle acidosis
3
- we don’t only save the bicarb but we can manufacture it
- glutamine – getting rid of the ammonium (leverage amino acids) to create bicarb
- that creates a titratable redox reaction
see images
Acid-base disturbance: recall and explain disturbances in acid-base balance (including respiratory acidosis, metabolic acidosis, respiratory alkalosis and metabolic alkalosis), and explain respiratory and metabolic compensation
fully compensation BE and pco2 abnormal in the same direction