Which of the following is an example of a homeostatic variable?

• A. Atmospheric pressure
• B. Room temperature
• C. Blood pH
• D. External humidity

Answer: (C)

Blood pH is an example of a homeostatic variable because it is a critical factor that the body regulates to maintain optimal functioning. The normal range for blood pH is tightly controlled between 7.35 and 7.45. Deviations from this range can lead to significant physiological disturbances, impacting enzyme activity, oxygen transport, and overall metabolic processes.

The body has various mechanisms in place to regulate blood pH, such as respiratory adjustments to carbon dioxide levels and renal excretion of hydrogen ions, which help to restore balance when pH levels fluctuate. This illustrates the concept of homeostasis, where the body actively maintains internal stability despite external changes.

In contrast, atmospheric pressure, room temperature, and external humidity are environmental factors that do not have the same regulatory mechanisms within the body. While these factors can influence bodily functions and overall comfort, they are not variables that the body actively regulates to maintain homeostasis.