Which system helps maintain blood pressure by regulating fluid balance and sodium retention?

Which system helps maintain blood pressure by regulating fluid balance and sodium retention?

• A. Sympathetic nervous system
• B. Natriuretic peptide system
• C. Hypothalamic-pituitary-adrenal axis
• D. RAAS

Answer: (D)

The system that maintains blood pressure by regulating fluid balance and sodium retention is the renin-angiotensin-aldosterone system. When kidney perfusion drops or sodium delivery to the distal tubule falls, renin is released and starts a cascade that produces angiotensin II. Angiotensin II causes blood vessels to constrict and stimulates aldosterone release from the adrenal cortex. Aldosterone tells the kidneys to reabsorb more sodium (and water follows), increasing blood volume and pressure. It also promotes thirst and vasopressin release, further helping to retain fluid. This mechanism acts over longer periods to sustain blood pressure through volume and salt control, whereas other systems have more immediate, different roles: the natriuretic peptide system promotes sodium loss and vessel dilation to lower pressure; the sympathetic nervous system adjusts heart rate and vascular tone quickly; and the hypothalamic-pituitary-adrenal axis has a broader stress-related influence with indirect effects on BP.

The system that maintains blood pressure by regulating fluid balance and sodium retention is the renin-angiotensin-aldosterone system. When kidney perfusion drops or sodium delivery to the distal tubule falls, renin is released and starts a cascade that produces angiotensin II. Angiotensin II causes blood vessels to constrict and stimulates aldosterone release from the adrenal cortex. Aldosterone tells the kidneys to reabsorb more sodium (and water follows), increasing blood volume and pressure. It also promotes thirst and vasopressin release, further helping to retain fluid. This mechanism acts over longer periods to sustain blood pressure through volume and salt control, whereas other systems have more immediate, different roles: the natriuretic peptide system promotes sodium loss and vessel dilation to lower pressure; the sympathetic nervous system adjusts heart rate and vascular tone quickly; and the hypothalamic-pituitary-adrenal axis has a broader stress-related influence with indirect effects on BP.