What is the role of the renin-angiotensin-aldosterone system (RAAS) in exercise?

• A. RAAS helps regulate blood pressure and fluid balance through vasoconstriction and renal sodium/water handling.
• B. RAAS primarily enhances muscle contraction via neural signals.
• C. RAAS reduces blood pressure during exercise.
• D. RAAS is inactive during exercise.

Answer: (A)

During exercise, the body needs to keep blood pressure and plasma volume stable as blood is redirected to working muscles. The renin-angiotensin-aldosterone system helps do this by responding to any drop in kidney perfusion. When renin is released, it kicks off a cascade that produces angiotensin II and aldosterone. Angiotensin II constricts blood vessels, which raises systemic blood pressure, while aldosterone increases sodium reabsorption in the kidneys (and water follows), expanding plasma volume. This combination helps maintain renal perfusion and blood pressure during activity and also supports fluid retention to combat dehydration. The system isn’t about enhancing muscle contraction through neural signals, nor is it inactive during exercise; it activates to preserve circulation and fluid balance as exercise continues.