Pain. Everybody knows what it feels like, and – apart from a few determined individuals – we tend to avoid it. But what is it? The International Association for the Study of Pain (IASP) defines it as:
“an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”
Or, in other words, when you damage yourself it hurts. And if you’re feeling down already, it hurts more. And if you’re not feeling down already, then pain may make you feel down. And then it will hurt more.
The IASP mainly looks at pain in humans, but it’s a long time since we stopped trying to pretend that animals either don’t feel pain like we do, or else don’t get upset about it. They do, and their inability to communicate pain effectively (or else our inability to properly listen) means that for a lot of animals, pain is a chronic, miserable constant in their lives, despite help being close to hand.
There are tiny pain receptors all over the body, inside and out, attached to nerve fibres. When a tissue is damaged, they’re triggered to send impulses up to the brain, which senses them and registers the feeling we call pain. Hard to describe, but we all understand what it is and we’ve all got experience of it. Pain receptors are usually well embedded in tissues, and usually need a fair bit of triggering – otherwise, any form of touch would be painful.