Which system reacts the slowest to pH changes?

The kidneys are the system that reacts the slowest to changes in pH. While they play a crucial role in maintaining acid-base balance in the body by adjusting the excretion or reabsorption of bicarbonate and hydrogen ions, this process can take hours to days to effect meaningful change.

In contrast, the lungs, which are involved in respiratory regulation of pH, can respond more rapidly by adjusting ventilation rates. The bicarbonate system provides an immediate but temporary buffer against pH changes without initiating long-term compensation. Therefore, in the context of managing acid-base status, the kidneys' slower response time is a distinguishing characteristic that underscores their vital function in stabilizing the body’s pH over a longer period.