A child with bacterial meningitis develops a rising temperature with vigorous shivering and peripheral vasoconstriction. Aspirin is given and sweating begins shortly afterwards. The sequence underlying these observations is best described as:

• A Aspirin directly cools the blood perfusing the anterior hypothalamus below the set point
• B Shivering generates pyrogens that act directly on skeletal muscle thermoreceptors
• C Vasoconstriction raises the hypothalamic set point while sweating lowers it independently
• D Pyrogens raise the hypothalamic set point, driving shivering and vasoconstriction until core temperature reaches the new set point; antipyretics reset it downward, triggering sweating and vasodilation ✓

Explanation

Endogenous pyrogens such as IL-1 induce prostaglandin E2 in the preoptic area, elevating the hypothalamic set point. Because core temperature now sits below the new set point, the body behaves as if cold, conserving heat by cutaneous vasoconstriction and generating it by shivering. Cyclooxygenase inhibition by aspirin lowers the set point back toward normal, so the body now perceives itself as hot and dissipates heat by sweating and vasodilation.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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