Goose bumps

Goose bumps are small bumps that appear on the skin. In American English, they are called goose bumps. In British English, people call them goose pimples. This physical reaction is known as piloerection or the pilomotor reflex. It is also sometimes called horripilation. These bumps occur at the base of body hairs. They happen when certain muscles in the skin tighten. This reaction is a common part of how many mammals interact with their environment.

The process of piloerection involves a specific biological mechanism. It begins with the sympathetic nervous system. This system manages the body's fight-or-flight responses. When the system is triggered, it sends signals to tiny smooth muscles. These are called arrector pili muscles, or APM for short. Each APM connects the hair follicle to the basement membrane. When these muscles contract, they pull the hair follicle straight up.

This contraction causes the skin to lift and form a bump. Scientists used actin immunofluorescence to visualize these muscle cells. While it was once thought one muscle connected to one hair, studies show one APM can connect to multiple follicles.

There are several different triggers for this reflex. One major cause is extreme temperature changes. If you enter a cold environment, your skin tries to re-balance its temperature. The cold stimulus causes the arrector pili muscles to contract. This helps with thermoregulation, which is how the body manages heat. In animals with thick fur, the upright hairs trap a layer of air. This air acts as insulation to keep the animal warm.

Strong emotions can also cause goose bumps in humans. This is often linked to intense feelings like fear, euphoria, or sexual arousal. You might experience them while watching a horror film or after winning a sports event. Some people even experience piloerection from hearing nails scratch on a chalkboard. Interestingly, some people can trigger these bumps on purpose. This is called voluntarily generated piloerection. Researchers are still studying why this happens. It seems to correlate with personality traits related to openness to experience.

Many other animals use piloerection for survival. For porcupines, raising their quills makes them more dangerous to predators. Sea otters raise their hair when they encounter sharks. Some animals use the reflex to look larger and more intimidating. This is called an intimidation display. Chimpanzees and certain monkeys, like the cotton-top tamarin, use this to scare enemies. Even cats and rodents like mice and rats show this reflex when they are frightened.

The term "goose bumps" comes from a visual comparison. When a goose is plucked, its skin has many small protrusions. These bumps look very similar to human skin during piloerection. Because of this, many languages use different birds for the name. In French, Spanish, and Japanese, the term refers to chicken skin. In Hebrew, the term uses the word for duck. In Ukrainian and Russian, the term refers to ants. This shows how different cultures use different animals to describe the same feeling.

Piloerection can also be a sign of medical conditions. It is a classic symptom of temporal lobe epilepsy and some brain tumors. It can also occur during autonomic hyperreflexia. In some cases, goose bumps are a sign of opiate withdrawal. The phrase "cold turkey" may come from this. It describes the bumps that appear during abrupt withdrawal from opioids. These bumps look like the skin of a refrigerated, plucked turkey.

Finally, it is important to distinguish between different sensations. Some people report feeling "chills" from music. However, research shows that the feeling of chills is a subjective experience. It does not always match the physical reality of piloerection. Piloerection is an objectively quantifiable physiological reaction. This means scientists can measure it physically. Understanding these differences helps researchers study how the body and mind work together.