I am trying to tailor what I talk about to what people are actually interested in knowing about. So this one goes out to a friend, who apparently got goose bumps on the metro this morning.
Goose bumps (science term: cutis anserina) are the tiny bumps everyone feels, mainly on your arms, when you are cold or emotionally moved. Goose bumps are actually a very simple thing to understand so I’m going to throw in some side info too.
Let’s say you are sitting on the metro and you are cold. Or say someone in crocs was asking if they could sit next to you (which scares you to death). In either case, your brain is going to know it needs to respond and it is going to tell the sympathetic nervous system to create the needed response. Neuronal shockwaves are going to fly through your body and some are going to hit the middle layers of your skin – this is where the roots of your hair follicles can be found. Attached to each hair follicle is a tiny little smooth muscle (an arrector pili muscle).
Little aside: Arrectores pilorum muscles are smooth muscles. That means you cannot control them. You can only control skeletal muscles. So sorry kids, you cannot control your goose bumps. Back to the metro …
Once these muscles get a neuronal signal they contract and pull the hair follicle straight up. Just like that, you have a goose bump!
Goose bumps make a lot of sense in other mammals. When an animal is cold, it can raise its hairs to trap warm air next to its skin. When an animal is frightened, it can raise its hairs to look bigger than it actually is. The best example of the latter is a porcupine, which uses its arrectores pilorum muscles to raise it quills. Mice and cats do this a lot too.
In humans, egh, not so much. We don’t have enough hair to make it effective. The ability to have goose bumps is considered a vestigial trait (a trait that has lost its helpfulness). Eventually we will probably lose the ability to get goose bumps though evolution.
So enjoy them now!
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