 The pH of the extracellular fluid, including the blood plasma, is normally tightly regulated between 7.32 and 7.42, by the chemical buffers, the respiratory system, and the renal system.Aqueous buffer solutions will react with strong acids or strong bases by absorbing excess hydrogen ions, or hydroxide ions, replacing the strong acids and bases with weak acids and weak bases.This has the effect of damping the effect of pH changes, or reducing the pH change that would otherwise have occurred.