Why does severe dehydration lead to a rapid drop in blood pressure, despite compensatory mechanisms, when plasma osmolality increases beyond a critical threshold?

💡 Explanation

Dehydration increases plasma osmolality, stimulating ADH release and thirst. However, if dehydration is severe, impaired baroreceptor sensitivity limits the heart's ability to increase cardiac output to maintain blood pressure because the baroreceptors cannot adequately respond to the hypovolemia. Therefore, blood pressure drops despite ADH and thirst mechanisms, rather than direct vasoconstriction or immediate sodium/potassium shifts.

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