Goose bumps can temporarily rise up on parts of your body when you feel a blast of cold air or hear a scary noise coming from outside the window. But what exactly makes your skin get all bumpy?

A physical or emotional feeling (like cold or fear) triggers an automatic surge of a hormone called adrenaline, which is often released when people feel chilly, afraid, or stressed-out in some way. This subconscious response in your nervous system causes tiny muscles in your hair follicles to contract. These hair-erector muscles, technically known as Arrectores pilorum, raise the follicles above the rest of your skin, and voila! You’ve got bumps.

Goosebumps are also commonly known as gooseflesh, and sometimes called "horripilation," which is a mix of the Latin words "horrere" (meaning to bristle or stand on end) and "pilus" (meaning hair). Funnily enough, doctors and other medical professionals call goose bumps by their technical name, "cutis anserina," which comes from the Latin words for skin ("cutis") and goose ("anser"). In other words, "goose skin." In other other words, it’s a much fancier way of saying "goose bumps."

Have you ever seen your cat’s hair stand on end when something startles it? Or noticed that your dog’s coat looks fluffier when it’s outside in the cold? Animals also have erector muscles that raise up their hair, but you’re not going to see goose bumps on something that furry! Having fluffier hair can make a threatened animal look bigger and maybe help it ward off an attacker, while a coat that’s puffed up in cold weather is better for insulating the animal and helping it to stay warm.