Goose bumps are created when tiny muscles at the base of each hair, known as
arrector pili muscles, contract and pull the hair straight up. The reflex is started by the
sympathetic nervous system, which is responsible for many
fight-or-flight responses. The muscle cells connected to the hair follicle have been visualized by actin immunofluorescence.
Arrector pili muscle Arrector pili muscles (APM) are smooth muscles which connect the basement membrane to the hair follicle. When these muscles contract, they increase the trapping of air on the surface of the skin and in turn, causes
thermoregulation to the body. It used to be believed that each APM was connected to an individual
hair follicle. More recent studies have disproved this and now explain that there can be multiple hair follicles connected to a single APM. In between the hair follicle and the APM there are lobules which form an angular shape. These lobules are
sebaceous gland lobules which are supported by the APM. 2)
Arrector pili muscle 3)
Hair follicle 4)
Dermis The diagram shows that the arrector pili muscle is connected to the hair follicle and the epidermis resulting in the erection of the hair during muscle contraction causing goose bumps.
Hair follicle Hair follicles have four parts. There is the bulb, supra bulbar area, isthmus and infundibulum. The bulb is to be known as the part that is responsible for the growth of the rest of the hair follicle.
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 In humans, goose bumps can even extend to piloerection as a reaction to hearing nails scratch on a chalkboard, or feeling or remembering strong and positive emotions (e.g., after winning a sports event), or while watching a
horror film. Some people can deliberately evoke goose bumps in themselves without any external trigger. This is called "voluntarily generated piloerection." Further research is needed to discover more on such people. Goose bumps are accompanied by a specific physiological response pattern that is thought to indicate the emotional state of being moved. In humans, goose bumps occur everywhere on the body, including 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, goose bumps tends to occur across the whole body, especially when elicited by thermal or emotional stimuli, and only locally when elicited via tactile stimuli. 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. == Causes ==