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Concept

piloerection

A creature with upright, golden-brown bristles on its back stands against a neutral background, demonstrating piloerection, the involuntary contraction of arrector pili muscles that causes hairs to stand up.

The involuntary contraction of the arrector pili muscles, tiny strands of smooth muscle anchored to each hair follicle, which pulls hairs upright. In furred mammals this traps an insulating layer of air against the skin or makes the animal look larger to threats. In modern humans, with negligible body hair, the reflex produces only the dimpled skin known as goosebumps, triggered by cold, fear, or strong emotion.

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