If a marathon runner experiences exertional heat stroke despite adequate hydration, which mechanism is most likely failing?

💡 Explanation

Failure in hypothalamic set-point adaptation, where the body's internal thermostat fails to regulate core temperature effectively during intense exercise, can lead to heat stroke, because the runner cannot dissipate heat adequately. Therefore, the hypothalamic regulation is the primary failure, rather than peripheral mechanisms like shivering or vasoconstriction which are secondary responses.

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