HOW PAIN WORKS: the basics
Updated: Sep 21, 2020
Pain is different to tissue injury, yet we commonly think of them as one and the same. Find out more about how pain works and how understanding this can deepen roots for pain care.
When your roots run deep, there is no need to fear the wind African proverb
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HOW PAIN WORKS:
THE DIFFERENCE BETWEEN PAIN AND NOCICEPTION
Picture this: you’re out hiking on a mountain and you roll your ankle. It hurts! You can see your ankle has started to swell and when try to put weight on it, it’s really painful. You assume you’ve done damage to your ankle, probably sprained the ligaments and that the injury has caused some inflammation. You assume that the pain you’re experiencing is coming from your ankle. Now, what if I said that all pain we experience is ultimately the output of our brains? And further, that the pain itself can’t biologically come from your ankle. Your natural reaction, a reasonable one at that, might be surprise or even disbelief…..clearly the pain is in your ankle and therefore must be coming from your injured ankle…but is it?
Let’s look biologically at what happens. When you roll your ankle, nerves called nociceptors are activated, sending signals from your ankle to your spinal cord, and then onto your brain to say that your ankle has been stretched and that there is potential danger in the area. The important thing is this isn’t pain at this point; nociceptors are “danger detectors” simply signalling to the brain that there is some potential danger in the body. (1-3)
Once this nociception has been transmitted to the brain, your brain must react and then try to make sense of this sensation, at the same time as taking in and processing lots of other information. In a split second, beyond your conscious control, your brain goes to work. Detecting potential threat to you and your tissues, your emotional brain (i.e. the limbic system consisting of areas such as the amygdala, insula and anterior cingulate cortex) is activated and begins to protect you, recruiting your motor cortex in the process. Instinctively you hop, take the weight off, maybe sit down and gingerly touch your foot to check for damage.(4) Other parts of your brain, like the insula and cognitive centers like the pre-frontal cortex and again anterior cingulate cortex, start to integrate information about the significance and impact of this suspected injury, like the fact that you’re on a cliff path, and you felt your ankle twist- your brain is making sense of what’s happened.(4,5) Your brain is also drawing on information from your past- have you sprained your ankle before and what were the consequences? And it’s drawing conclusions about the consequences of you spraining your ankle a mile from your car on a mountain- how will you get back? Is it safe to move? Do you need an x-ray?
Your brain’s job right now is to decide how much threat you and your body part are in. If the brain decides on investigation that you/your tissues are under threat, you will experience pain as part of your body’s natural, in-built protective mechanisms. If the brain, for whatever reason computes that you are not under threat or indeed if something else is going on that’s more important, then you will experience less pain or no pain right now. (2) Saying that “the brain decides” often makes it sound like this happens under our conscious control. We’ll talk about this later as we explore the brain in more detail but at least initially much of this occurs really quickly and outside our conscious control. (4)
And so, pain really is the output of the brain but it’s the result of many inputs from tissue sensations to what we think, our attention and focus, memory and our emotional states. Ultimately, as a main survival tool, pain’s job is to protect us. It’s a very important job, but as we’ll see in the next few blogs, sometimes our nervous system can become over-protective (or sensitized) and we experience pain even when there’s little or no danger or damage.
Understanding pain may also allow us to utilize the breadth of our professional skills to address some of the multiple areas for pain care and integrate yoga as part of this pain care.
WHY DOES KNOWING THIS MATTER?
Pain is a normal human experience for all of us. Understanding how it works allows us to move beyond thinking that the pain people experience is always directly related to tissue injury. A broader understanding of the balance between physical injury and inflammation with how the nervous system reacts (as well as immune and endocrine system responses) allows much greater scope to explore multiple avenues back to health.
1. Butler DS. The Sensitive Nervous System. Adelaide: Noigroup Publications; 2000.
2. Butler D, Moseley LG. Explain Pain. Adeliade: Noigroup Publications; 2003.
3. Woolf CJ, Ma Q. Nociceptors--noxious stimulus detectors. Neuron. 2007;55(3):353-364.
4. Lumley MA, Cohen JL, Borszcz GS, et al. Pain and emotion: a biopsychosocial review of recent research. Journal of clinical psychology. 2011;67(9):942-968.
5. Wiech K, Lin CS, Brodersen KH, Bingel U, Ploner M, Tracey I. Anterior insula integrates information about salience into perceptual decisions about pain. The Journal of neuroscience : the official journal of the Society for Neuroscience. 2010;30(48):16324-16331.