The Gate Control Theory of Pain
We are all familiar with the fact that various things can change how different people, or equally the same person at different times, can feel or react to pain. This is something we all experience. We have looked in the Pain Pathways page at the way that the "wiring" in the body carries pain from the periphery to the brain, but the situation is far more complex than a simple electrical connection. Other nerve activity coming into the dorsal horn in the spinal cord affects the processing of pain nerve (noxious) impulses at that level, and impulses descending from the brain also have effects. This explains why things like "rubbing it better" can help, as we have all learned.
Ronald Melzack and Patrick Wall published their paper (Melzack R, Wall PD. Pain mechanisms: a new theory. Science. 1965 Nov 19;150 (699): 971–979) on the gate control theory of pain in 1965. Although now further developed, this theory hugely changed our understanding of pain.
Pain impulses travel into the spinal cord carried along small fibres, classed as A-delta and C fibres. There, in the dorsal horn at the back of the spinal cord, in a specialised area called the substantia gelatinosa, these small nerves talk to other nerves which in turn travel up the spinal cord carrying the impulses. This communication can be reduced (shutting the Gate) by other larger nerves such as those carrying touch, which stimulate little connecting nerves called interneurons, these interneurons affecting the communication between the small nerves and the other nerves. This works by the release of chemicals including the body's own morphine-like chemicals, enkephalins. This explains how rubbing it better can help, and also is the mechanism behind some of the effects of acupuncture and the use of TENS machines.
In addition, other factors such as what is going on in our minds such as distraction, stress and attention to other things can reduce pain. This works through nerve pathways descending down through the spinal cord and feeding into the gate control mechanism through the interneurons.
These mechanisms are discussed in more detail in this article.
How Gate Control Theory has changed how we view Pain
• We now view pain as a perception rather than a sensation
• We feel pain actively rather than passively, interpreting and appraising the stimuli
• The many factors involved, and our own individual make-up, cause variation in how we feel and react to pain.
• Understandng of gate control and how psychological and other factors affect it explains why pain is never just "in your body" or "in your head" alone, but is an interaction between the mind and body.
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Page updated 22/6/2016