Why does sustained strenuous exercise in a hot environment cause increased plasma osmolality to trigger thirst more effectively than after rapid intravenous saline infusion?

💡 Explanation

Sustained exercise increases angiotensin II levels because renal hypoperfusion stimulates renin release; this synergizes with increased plasma osmolality to enhance thirst drive. Therefore, the thirst response is more pronounced, rather than being solely driven by osmolality as with saline infusion.

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