Why do we get goosebumps when the water is cold or when we get out of it?
When faced with cold, the brain sends a signal that causes the small erector muscles located at the base of the hairs, under the skin, to contract. In addition to releasing a small amount of heat, the contraction of these arrector pili muscles, also called "arrector pili," causes the hairs to stand up to form an insulating layer, which is supposed to retain body heat. While this worked well for our ancestors with much more developed hair, in us, the tiny bumps that appear on the skin make us look more like a plucked chicken, hence the term "goosebumps."
The principle is the same when we are afraid. Here again, it is a reflex inherited from our ancestors, whose hair stood on end to make them appear more imposing in the face of potential danger.
And coming out of the water…As for the chills we sometimes get when getting out of the water, they are due to the evaporation of water from the surface of our skin, which causes our body to cool . And, once again, our brain will send a signal to our horripilator muscles to make our ancestral fur, which is supposed to conserve our body heat, stand up.
