The phenomenon of getting goosebumps when you feel excited, emotional, or experience something pleasurable is known as piloerection or the pilomotor reflex. It is a natural physiological response that occurs in both humans and many animals. This response is a relic of our evolutionary past and is associated with the "fight or flight" response.
When you experience strong emotions like excitement, joy, or pleasure, your brain may activate the autonomic nervous system, which is responsible for controlling involuntary bodily functions. This includes the sympathetic nervous system, which is involved in the "fight or flight" response. One of the reactions triggered by the sympathetic nervous system is the contraction of tiny muscles at the base of your hair follicles, known as arrector pili muscles.
These muscles contract when stimulated by the sympathetic nervous system, causing the hair follicles to be pulled upright. In animals, this response serves to make them appear larger and more intimidating to potential threats, as their fur stands on end. However, in humans, our body hair is not dense enough for this effect to be noticeable, but the response still occurs.
The term "goosebumps" comes from the visual appearance of the skin when these muscles contract – it looks similar to the skin of a plucked goose. The feeling of having goosebumps is caused by the skin becoming slightly raised or elevated, which may be more pronounced in areas where body hair is present.
In addition to emotional responses, other factors such as cold temperatures or experiencing a sudden fright can also trigger the pilomotor reflex. It's a fascinating example of how our bodies retain some reflexes from our evolutionary history, even though they might not have the same practical significance for modern humans.