Library · Physiology
Goosebumps
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Goosebumps have a technical name, piloerection, and they are something very specific: each hair stands on end because a muscle pulls on it.
That muscle is called the arrector pili, and it is a bundle of smooth muscle fibers, the kind that does not move on command. It sits in the dermis, the middle layer of the skin, and it runs from a bulge on the hair follicle, the little pouch each hair grows out of, up to just beneath the epidermis, the layer above. Every hair comes with its own tiny muscle to straighten it.
The signal comes from the sympathetic nervous system, the part of the nervous system that responds without any decision on your part, and it is triggered by cold or emotion. As the hairs rise, they trap a layer of air underneath, and that air helps hold in heat.
The same contraction does something else: it helps the sebaceous gland push out its sebum, the oil that lubricates hair and skin.
In brief
Goosebumps, or piloerection, happen when the arrector pili muscle contracts and the hair stands up.
That muscle is a bundle of smooth muscle fibers in the dermis, running from the bulge of the hair follicle to just under the epidermis.
Every hair comes with its own tiny muscle to straighten it.
The sympathetic nervous system triggers it in response to cold or emotion, and raised hair traps a layer of air that holds heat.
The same contraction helps the sebaceous gland push out its sebum.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingAnatomy, Hair Follicle, StatPearlsPublished
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