Brain freeze is a brief headache set off by very cold food or drink on the palate. Its exact mechanism is still debated, involving the trigeminal nerve and blood flow.
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No. The head loses heat roughly in proportion to its share of body surface, about 7 to 10 percent. The myth persists because heads are often the only uncovered part in the cold.
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No. Hair and nails do not keep growing after death. They look longer because the skin dries out and shrinks back, which creates an optical illusion.
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No. Alcohol makes your skin feel warmer by shifting blood to the surface, but this speeds up heat loss and can lower your core temperature, especially in the cold.
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A hiccup is an involuntary diaphragm spasm followed by a sudden closing of the vocal cords. The triggers are well known, but why the reflex exists is still unsettled.
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Wrinkling is mainly an active nerve-driven response: blood vessels in the fingertips narrow and the skin puckers. It may help grip wet objects, though that purpose is still debated.
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Goosebumps are an involuntary reflex in which tiny muscles pull hairs upright. It is a leftover from furrier ancestors, triggered by cold and by strong emotion.
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