Oh, not entirely sure about this one – suspect it may have to involve muscle contraction of some sort. Isn’t this a response that’s not so useful for humans but is of more benefit to furrier animals when they are cold since it increases the thickness of the insulating layer formed by their coat?
Hey popthebottle i didn’t know the answer to this but I have found an answer on the internet (good old internet!) It said that the reaction of the nervous system (caused by cold/excitement as you said) causes the heart to beat more quickly and sends blood rushing to the muscles, including the very small muscles called “arectores pilorum,” which are attached to the hair follicles in the skin and causes goose pimples!
Theres a little muscle at the root of each hair which can contract to make your hair stand on end. This can trap air near to your skin (which is good for keeping you warm).
In our hairier relations it can also be used to send signals to other members of the group about fear aggression and excitement. I am guessing this is why we sometimes still get goosebumps in these situations even though in humans it would be pretty difficult to notice them unless you were really looking.