Which control mechanisms are involved in maintaining fluid balance?

Which control mechanisms are involved in maintaining fluid balance?

• A. RAAS, natriuretic peptide system, and ADH.
• B. Respiratory rate alone.
• C. Bone remodeling.
• D. Gastrointestinal absorption only.

Answer: (A)

Fluid balance is controlled mainly by hormonal systems that regulate how the kidneys handle salt and water. The renin-angiotensin-aldosterone system responds to lower effective circulating volume or low sodium by increasing sodium reabsorption and promoting water retention, which raises blood volume. The natriuretic peptide system is activated by stretch from increased volume and works to lower volume by promoting sodium and water excretion. Antidiuretic hormone (ADH) is released when plasma osmolality rises or blood volume falls, increasing water reabsorption in the collecting ducts to restore balance. Together, these mechanisms finely regulate extracellular fluid volume and osmolality. Other options don’t represent primary regulators of fluid balance. Respiratory rate affects acid-base balance rather than direct fluid regulation; bone remodeling is not involved in maintaining fluid balance; gastrointestinal absorption influences intake but is not a regulatory mechanism that maintains fluid balance.

Fluid balance is controlled mainly by hormonal systems that regulate how the kidneys handle salt and water. The renin-angiotensin-aldosterone system responds to lower effective circulating volume or low sodium by increasing sodium reabsorption and promoting water retention, which raises blood volume. The natriuretic peptide system is activated by stretch from increased volume and works to lower volume by promoting sodium and water excretion. Antidiuretic hormone (ADH) is released when plasma osmolality rises or blood volume falls, increasing water reabsorption in the collecting ducts to restore balance. Together, these mechanisms finely regulate extracellular fluid volume and osmolality.

Other options don’t represent primary regulators of fluid balance. Respiratory rate affects acid-base balance rather than direct fluid regulation; bone remodeling is not involved in maintaining fluid balance; gastrointestinal absorption influences intake but is not a regulatory mechanism that maintains fluid balance.