What are arrector pili? What do they do?

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1. Arrector pili are small, smooth muscles located in the dermis of the skin, attached to hair follicles.
2. These muscles are responsible for causing hair to stand on end, a phenomenon commonly known as 'goosebumps.'
3. When the arrector pili muscles contract, they pull the hair follicle upright, which can trap an insulating layer of air, helping to retain heat.
4. The contraction of these muscles is typically involuntary and can be triggered by cold temperatures or emotional responses such as fear.
5. This response is a vestigial reflex, meaning it is a remnant of an evolutionary trait that was more useful to our ancestors, who had more body hair.

Key Concepts

Arrector Pili Muscles

Arrector pili are small, smooth muscles attached to hair follicles in mammals. When these muscles contract, they cause the hair to stand upright, a phenomenon known as piloerection. This reaction is often associated with cold temperatures or emotional responses, such as fear, and is part of the body's mechanism to retain heat or appear larger to potential threats.

Piloerection

Piloerection is the process by which hair stands erect due to the contraction of arrector pili muscles. This response can be triggered by various stimuli, including cold temperatures and strong emotions. In addition to its role in thermoregulation, piloerection can enhance the appearance of an animal, making it look more formidable to predators or rivals.

Function of Arrector Pili

The primary function of arrector pili muscles is to facilitate piloerection, which serves both physiological and psychological purposes. Physiologically, it helps in thermoregulation by trapping air for insulation. Psychologically, it can signal emotional states, such as fear or aggression, contributing to the animal's overall survival strategy in response to environmental challenges.