What are goose bumps

A.� Goose bumps, sometimes known as goose flesh or goose pimples, or technically cutis ansirina, (which translates from the Latin as goose skin) are a temporary change in the appearance of the skin, usually when you're cold, angry or scared. Your skin becomes bumpy and the hairs on your arms stand on end.

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Q.� What makes the hairs stand up

A.� The stimulus that makes us feel cold or scared kicks off an involuntary nerve discharge which causes the muscles that pull up our body hair, called the arrectores pilorum muscles, to contract. This contraction makes our hairs stand on end and the hair follicles become raised bumps: goose bumps.

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Additionally this contraction makes the sweat glands smaller, so heat can't escape as readily.

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Q.� Why do I get goose bumps

A.� For two possible reasons. If you're goose bumps are caused by being cold, the erect body hairs trap air escaping from the body, acting as extra insulation.

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Alternatively if you've got goose bumps through fear or anger your bristled body hair makes you appear bigger than you actually are, scaring off aggressors.

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Q.� But I'm not covered in hair, so why do I get goose bumps

A.� Yes you are, it's just very fine. Goose bumps and the advantages they provide are a vestige from the days when humans were covered with thicker hair.

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Although we don't have enough thick body hair to provide extra insulation when it stands up anymore, we probably did in the distant past. Other, still furry, animals take advantage of their hair standing on end. Dogs and cats have enough hair to make difference to their body temperature if it stands on end when they're cold.

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Similarly, when threatened, they can appear bigger than they actually are by fluffing up their hair, making a potential attacker think twice.

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Have you got a question about why something happens Click here to ask.

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by Lisa Cardy