Then, [Mr Hammerhead Shark], his shirt covered in blood, spun around and hit his knee on the table, at which point he swore and yelled “My knee! My knee!,” the whole time unfussed about the hammer stuck in his neck.
G Lorimer Moseley. Painful yarns. Metaphors & stories to help understand the biology of pain. Canberra: Dancing Giraffe Press, 2007
Even the simplest biological organisms can protect themselves from threatening stimuli—by altering their path of movement away from the source of the threat.1 As evolution has honed us into more and more sophisticated creatures, we have also honed this fundamental capacity to protect ourselves from threat. Indeed, humans have very sophisticated methods of protection, perhaps none more sophisticated than pain. This chapter includes:
some examples of the “fearful and wonderful complexity” of pain, which are conveyed by
proposing a contemporary definition of pain that is contrary to conventional definitions but which integrates the huge amount of research that has been undertaken since our conventional definitions were established
introducing the idea of nociception and describing some of what is known about the biological mechanisms that underpin nociception
providing a conceptual framework with which to make sense of pain within the context of clinical practice
a very practical clinical approach to considering referred pain when managing patients.
COURTESY OF MALCOLM WILLETT
Almost everyone experiences pain. Those who do not experience pain as the rest of us know it are at a distinct disadvantage in life and are likely to die young without living fast. Pain is an unpleasant sensory and emotional experience that is felt in the body and that motivates us to do something to escape it. These two characteristics of pain—its unpleasantness and its anatomical focus—are what makes it such an effective protective device. Pain alerts us to tissue damage or the threat thereof. Pain makes us seek attention. Pain changes our behavior. Pain stops us competing, keeps us seeking a cure, and compels us to prioritize pain relief above almost everything else. In fact, if the brain concludes that there is something more important than protecting a body part, then it makes the executive decision to not produce pain. Therein lies the key to really understanding pain—it is as simple and as difficult as this—if the brain concludes that a body part is in danger and needs protecting, and you, the organism, ought to know about it, then the brain will make that body part hurt.2
This concept of pain integrates a vast body of basic, applied, and clinical research. It differs greatly from conventional theories, which have changed little since the seventeenth century when Rene Descartes was ridiculed for suggesting that we were not made from four bodily humors.3