Acid-base Flashcards
Alkalosis:
- pH?
- CNS symptoms?
- Cause?
- pH > 7.45
- Drowsy, headache, convulsions
- Vomiting
Acidosis:
- pH
- Symptoms
- Cause?
- pH < 7.35
- drowsy, respiratory disfunction, coma
- Diarrhea
pH of urine
4.5-8 (diet dependent)
pH of gastric acid
1
pH of pancreatic fluid
7.8
pH of blood/ECF
7.4 (tightly regulated b/w 7.35 - 7.45)
pH of cell
7.1
Why regulate pH?
- Influences pH activity
- Regulates ion transport
- Needed for cell growth, metabolism, DNA synthesis
- CNS (alkalosis + acidosis)
Sources of H+ gain
- Generation of H+ from CO2 (hypoventilation)
- Production of non-volatile acids
- Loss of bicarbonate (i.e. diarrhoea, urine)
Sources of H+ loss
- Using H+ in the metabolism of anions
- Vomit
- Urine
- Hyperventilation
What reaction occurs in the body when CO2 is produced by cells? (with the help of which enzyme)
CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-
First reaction requires carbonic anhydrase
How is H+ buffered in transit?
How is it removed from the lungs?
- Haemoglobin
- Takes up H+ produced in cells (HHb)
- Releases H+ in lungs (O2Hb-)
The H+ in the lungs then goes on to form CO2
Why do we need to breathe at a continuous rate?
To prevent hypo-/hyperventilation and thus acidosis/alkalosis
What are the 3 main buffering mechanisms in the body?
- Bicarbonate
- Protein
- Phosphate
How does the kidney handle bicarbonate?
- Reabsorption of filtered HCO3-
- Replacement of HCO3- consumed in excretion of non-volatile acids
- Excretion of excess HCO3-
How is filtered bicarbonate reabsorbed in the body?
- Carbonic anhydrase catalyses the formation of carbonate from CO2 and H2O in the epithelial cells
- The carbonate dissociates into H+ ion and bicarbonate
- The bicarbonate is absorbed into the interstitial fluid
- The H+ ions are secreted into the lumen (coupled with Na+)
- The H+ ions combine with bicarbonate in the filtrate to form carbonate, which is secreted as H2O and CO2
Note: no new bicarbonate is formed
How is bicarbonate replaced?
- Carbonic anhydrase catalyses the formation of carbonate from CO2 and H2O in the epithelial cells
- The carbonate dissociates into H+ ion and bicarbonate
- The bicarbonate is absorbed into the interstitial fluid
- The H+ ions combine with filtered non-volatile acids (anions), e.g. (HPO4)2-
- The acid is excreted e.g. H2PO4-
What is compensation? (In terms of body pH balance)
If one variable changes, you can get the pH back to normal by changing the other variable to restore the ratio to 20:1
What are the 2 respiratory disturbances?
- Excess CO2
- Hypoventilation
- Acidosis - Not enough CO2
- Hyperventilation
- Alkalosis
What are the 2 metabolic disturbances?
- Excess bicarbonate
- Acid shortage
- Alkalosis - Not enough bicarbonate
- Excess acid
- Acidosis
What is the Henderson-Hasselbalch equation? (in terms of the body)
pH = 6.1 + log(conc. of bicarbonate / (0.03xpCO2))
What is the ratio of bicarbonate to (0.03 x pCO2)?
20:1
