What causes physical pain? Why do cuts hurt?


What is it that makes a cut in your skin feel painful? Such as a paper cut or a cut with a knife. Why does this register as pain?

In: Biology

Your brain receives a signal from a nerve that it’s been damaged, so it alerts you by putting pain there. The pain is uncomfortable so you have an incentive to figure out the cause an stop it.

A cut exposes the nerve to air, that triggers a strong pain response. Covering the wound can reduce the pain quickly, using something air tight like a liquid bandage can in some cases reduce felt pain to almost zero.

It’s actually a much more complex system than a surface level or eli5 type explanation can fully elucidate.

At the most basic it’s nerves sending signals that are interpreted by the brain.

But that brain part is a whole can of worms. The difference between neutral sensation and pain can come down to psychology. Pain is a warning but not all pain means something bad or damaging is happening. There are now therapies that teach chronic pain sufferers about pain and how to think about it differently that can lessen or even stop pain completely.

So imagine you get a repetitive stress injury. After totally healing people will still sometimes feel pain when doing the activity that caused the injury, when no damage is taking place. The brain has habituated itself to become more wary of sensations from the part of the body that was injured. After the kind of therapy I mentioned, a significant fraction of people with this problem can lessen or eliminate that….. uh, phantom pain, after having rehabituated their brain to accept more neutral sensations as not damaging and therefore not painful.

So, in short, though there are a lot of factors we still don’t understand about the brain and how it interprets the signals it receives from our nerves, one thing is totally clear: cognition is a feedback loop. Even sub- or unconscious processes are subject to this and can be “trained” by taking advantage of it.