The arrector pili muscle, also known as the pilomotor muscle, is a small muscle attached to each hair follicle in mammals. The contraction of these muscles causes the hair to stand up, resulting in „goosebumps” on the skin. So, why does the arrector pili muscle contract?

There are two primary reasons for the contraction of the arrector pili muscle. The first reason is related to temperature regulation. When we feel cold, the muscles contract, pulling the hair upright and trapping a layer of air between the hair and the skin. This layer of air acts as insulation, trapping body heat and keeping us warm. In a similar way, when we feel hot, the muscles relax, allowing the hair to lie flat against the skin and promoting heat loss through sweating.

The second reason the arrector pili muscle contracts has to do with emotional response. When we experience strong emotions such as fear or excitement, the muscles can contract involuntarily, leading to the appearance of goosebumps on the skin. This response is related to our evolutionary past and the flight or fight response. When animals feel threatened, their hair stands on end, making them look larger and more intimidating to potential predators. While this response may be less useful for humans today, it is still an important part of our physiology.

In addition to these primary reasons, there are other factors that can cause the arrector pili muscle to contract. For example, certain medications or conditions can affect the muscles` functioning, leading to excessive or inadequate contraction. Additionally, some people may experience persistent goosebumps or enlarged hair follicles due to a genetic condition known as pilomotor hyperreflexia.

Overall, the arrector pili muscle plays an important role in our physiology, helping to regulate our body temperature and providing a physical response to strong emotions. While it may not be a muscle that we pay much attention to, it is an important part of our overall health and well-being. As with any aspect of our physiology, it is important to pay attention to any changes or abnormalities and seek medical attention if necessary.