What is the physiologic term for maintaining a stable water balance?

• A. Water balance
• B. Electrolyte balance
• C. Blood pressure stability
• D. Oxygen homeostasis

Answer: (A)

Maintaining a stable water balance means keeping the body's water content within a narrow range despite varying intake and losses. This balance is achieved when water input (drinking, metabolic water) roughly equals water output (urine, sweat, respiration, stool). In physiology, this is described as water balance or fluid balance, and it’s tightly regulated by mechanisms like thirst and the kidneys’ ability to concentrate or dilute urine under the influence of hormones such as antidiuretic hormone.

This concept is distinct from electrolyte balance, which concerns the concentrations of charged particles (sodium, potassium, chloride, etc.), from blood pressure stability, which is about maintaining adequate circulatory pressure, and from oxygen homeostasis, which deals with maintaining proper oxygen levels. So the term that best describes maintaining a stable water content is water balance.