Defining Pain




Defining pain. The idea of this overview is to break down some of the complex terminology that comes up when discussing concepts of pain and pain models. I want to extract some of textbook definitions and break them down into more detail. My hope by the end of this short clip is to construct a framework of pain concepts that we use to build upon as we discuss more complex topics of pain in the future.


The most accepted definition of pain in the medical community was put out by The international association for the study of pain and is as follows. Pain is “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” Now that’s a mouthful so let’s break it down into its parts.


Basically the experience of pain requires 2 things: (#1) is a sensation that is perceived as painful or unpleasant AND (#2) is an emotional response or cognitive processing of the experience. Meanwhile, the definition also accounts for the fact that pain does not necessarily correlate with tissue damage.


So now let’s apply this definition of pain to the process by which the body senses pain. One other definition I want to review before going on is nociception since it’s a fundamental component of pain. Nociception is the encoding and processing of unpleasant and potentially harmful stimuli. So when applied to the definition of pain, nociception describes that initial component, that sensory component of pain without the cognitive processing of pain.


So let’s see how this works. There are peripheral sensory neurons called nociceptors that are located within the skin, muscle, skeletal structures, and viscera whose job it is to detect noxious, harmful, or unpleasant stimuli. Specifically, these sensory neurons are programmed to detect really high or low temperature, extreme pressure, and potentially harmful chemicals (these can be external corrosive chemicals or chemical changes in the body like lactic acid build up). These noxious stimuli are detected by receptors located in one end of the neuron. The nociceptor then encodes this information and sends it on to the brain and spinal cord for processing.


Just to review, pain is a sensory and emotional experience with or without actual tissue damage. Nociceptors are the peripheral receptors that detect the noxious stimulus and nociception is the process by which information from nociceptors about noxious stimuli is encoded and communicated to the peripheral and central nervous system.

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