Blood pH is normally regulated by the respiratory system to

Blood pH is normally regulated by the respiratory system to control the level of CO2 (g) and by the urinary system to control the levels of HCO3 - and non-volatile acids in the blood.

Solution

The body is constantly threatened from acid resulting from diet and metabolism. The stability of blood pH is maintained by the concerted action of chemical buffers, the lungs and the kidneys. Numerous chemical buffer (CO₂/HCO_3, phosphates) work together to maintain the pH changes in the body. The concentration ratio (base/acid) of any buffer pair, together with the pK of acid, automatically defines the pH.

The bicarbonate/carbon dioxide buffer is effective in buffering the body because its components are present in large amounts and the system is open. The respiratory system influences the plasma pH by regulating the pCO₂ by changing the levels of alveolar ventilation. The kidneys influence plasma pH by getting rid of acid or base in the urine.

Renal acidification involves three processes: reabsorption of filtered HCO₃^- , excretion of titrable acid, and excretion of ammonia. New HCO₃^- is added to the plasma and replenishes depleted HCO₃^- .

The stability of intracellular pH is ensured by membrane transport of H⁺ and HCO₃^- by intracellular buffers and metabolic reactions.