Pilomotor - Anatomy and Biology

Anatomy and Biology

Goose bumps are created when tiny muscles at the base of each hair, known as arrector pili muscles, contract and pull the hair erect. The reflex is started by the sympathetic nervous system, which is responsible for many fight-or-flight responses.

As a response to cold: in animals covered with fur or hair, the erect hairs trap air to create a layer of insulation. Goose bumps can also be a response to anger or fear: the erect hairs make the animal appear larger, in order to intimidate enemies. This can be observed in the intimidation displays of chimpanzees, some New world monkeys like the cotton-top tamarin, in stressed mice and rats, and in frightened cats. In humans, it can even extend to piloerection as a reaction to hearing nails scratch on a chalkboard, listening to awe-inspiring music, or feeling or remembering strong and positive emotions (e.g., after winning a sports event). During the formation of goose bumps, the body is warmed from the muscle tension in piloerection.

In humans, goose bumps are strongest on the forearms, but also occur on the legs, neck, and other areas of the skin that have hair. In some people, they even occur in the face or on the head.

In humans, the areolas of the breasts of females typically show piloerection because of hormonal distribution, for example, when aroused or inside the maternity cycle.

Piloerection is also a classic symptom of some diseases, such as temporal lobe epilepsy, some brain tumors, and autonomic hyperreflexia. Goose bumps can also be caused by withdrawal from opiates such as heroin. A skin condition that mimics goose bumps in appearance is keratosis pilaris.