Well, we really haven’t talked much about pain yet, have we? From the start I want to point out that in a normal functioning, healthy body, pain is probably not the evil villain we make it out to be. Pain serves a very important purpose – it alerts our body that something is wrong and threatening to harm our body and forces us to stop whatever it is that is about to damage our body, whether we are about to burn our bodies or if we are working them to the point our joints are about to experience damage. It also can alert us to get something checked out before more serious conditions develop.
Viewed from a slightly different perspective, let’s imagine a world
where we have our same bodies, subject to deterioration, only let’s imagine we can’t feel pain. So when we go about a normal day’s work, when
we would start to feel pain we would not. You’re probably already thinking about how much more work you would get done. Now I want you to guess how long you think this could go on before you would have broken bones and totally wore out joints, etc. Do you get the picture?
Let’s notice one way the body processes pain. Your body has various receptors, or sensors, in its tissues which send information about the body to the brain. Two such receptors are mechanoreceptors and nociceptors. To give a simple explanation, Mechanoreceptors tell the brain where the body is in space. When you move your arm with your eyes closed, you don’t need to open your eyes to tell you what position your arm is in; your body already knows that thanks to your mechanoreceptors. Nociceptors, on the other hand, are free nerve endings that fire off a message when the body is exposed to noxious or harmful stimuli.
The firing of a nociceptor, called nociception does not always result in
the body feeling pain. This is because the nociceptive activity must travel all the way up a certain tract in your spinal cord (called the spinothalamic
tract), and enter the brainstem before the brain recognizes it as pain. If the nociceptors are inhibited, or shut down before entering the brainstem, there are no symptoms. In fact, I read one statistic that mentioned 90% of all nociceptor activity never reaches the brain. This is because there are specific criteria or factors that determine whether nociception ever reaches the brainstem and becomes pain. The major factors are the intensity of the stimulus, the duration of the stimulus, and something called inhibition.
I mentioned mechanoreceptors with nociceptors for a reason. This is because the signals from mechanoreceptors compete with nociceptors. You probably knew this for a long time, only you didn’t think about it in this way. Let me illustrate. Have you ever hit your finger with a hammer? Did you find yourself shaking that finger afterwards? That’s because when you caused your mechanoreceptors to fire by shaking your hurt finger, you didn’t feel the pain. You caused the duration of the mechanoreception to exceed the duration of the nociception.