Why wouldn't the acids in the venous system (lactic, pyruvic) increase the pH?
JPINFV (and anyone else who can answer)- talk to me about this buffer system or throw a link please; i'm very interested.
I know there were some links, but here's a very quick and basic run-down of the bicarbonate-buffer system.
The normal equilibrium equation for normal blood is as follows:
(H20)+(CO2) <-> (H2CO3)+(H2O) <-> (HCO3-)+(H3O+)
If it works correctly, the CO2 equalizes through carbonic acid (H2CO3) into hydronium ions (H3O+) and bicarbonate ions (HCO3-). When it works, this keeps the pH of the blood between 7.35 and 7.45. When it doesn't work, the pH can change, as Le Chetelier's principle takes effect.
When it doesn't work, there are 4 basic things that can happen: respiratory acidosis, respiratory alkalosis, metabolic acidosis, and metabolic alkalosis.
Respiratory acidosis:
This results when the patient has too much CO2 in their system, which can result from hypoventilation or something else. This causes the equilibrium reaction to proceed like this:
(H20)+(CO2) -> (H2CO3)+(H2O) -> (HCO3-)+(H3O+)
In other words, more CO2 leads to an increase in the amount of carbonic acid which leads to an increase in the amount of bicarbonate ions and hydronium ions. An increase in hydronium ions leads to a drop in the pH of the blood (provided the buffer system can't overcome it).
Respiratory alkalosis:
This is along the same lines as respiratory acidosis, except instead of an increase in CO2 there's a deficit of CO2. This results in the following equilibrium reaction:
(H20)+(CO2) <- (H2CO3)+(H2O) <- (HCO3-)+(H3O+)
The reaction shifts to the left, to make up for the lack of CO2. This reduces the amount of hydronium ions, which results in a higher (and thus more basic) pH.
Metabolic alkalosis:
This results when a condition causes the pH of the blood to rise, and thus become more basic. This results in the following equilibrium equation:
(H20)+(CO2) -> (H2CO3)+(H2O) -> (HCO3-)+(H3O+)
Due to the drop of the pH on the right side of the equation, the equation shifts to the right to try to balance itself out. If the buffer system can't overcome the change in alkalinity, it can effect breathing and other things.
Metabolic acidosis:
This is the final one. When this occurs, such as in diabetic ketoacidosis, there is an excess of acid put into the bloodstream. This causes the equation to shift to the left:
(H20)+(CO2) <- (H2CO3)+(H2O) <- (HCO3-)+(H3O+)
The increase in acidity of the blood causes the amount of CO2 to increase, which causes hyperventilation as the body tries to rid itself of the extra CO2.
I hope this helps!
Eric