Why does severe dehydration rapidly induce intense thirst, despite the body's attempt at fluid conservation through increased ADH and water reabsorption in the kidneys' collecting ducts?

💡 Explanation

Thirst is triggered by elevated plasma osmolality detected by hypothalamic osmoreceptors. Because severe dehydration leads to a rapid increase in plasma osmolality, exceeding the threshold for thirst stimulation, it dominates despite ADH's water conservation efforts; therefore, thirst prevails, rather than ADH fully compensating rapidly enough.

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