Pain Gate

gate control theory pain 

Melzack and Wall introduced their “gate control” theory of pain in the 1965 Science article “Pain Mechanisms: A New Theory”. The authors proposed that thin (nociceptive) and large diameter (inoccuous) nerve fibers carry information from the site of injury to two destinations in the dorsal horn of the spinal cord: the “inhibitory” cells and the “transmission” cells. Signals from both thin and large diameter fibers excite the transmission cells, and when the output of the transmission cells exceeds a critical level, pain begins. The job of the inhibitory cells is to inhibit activation of the transmission cells. The transmission cells are the gate on pain, and inhibitory cells can shut the gate. When thin (pain) and large (touch, etc.) fibers, activated by a noxious event, excite a spinal cord transmission cell, they also act on its inhibitory cells. The thin fibers impede the inhibitory cells (tending to leave the gate open) while the large diameter fibers excite the inhibitory cells (tending to close the gate). So, the more large fiber activity relative to thin fiber activity coming from the inhibitory cell’s receptive field, the less pain is felt. The authors had conceived a neural “circuit diagram” to explain why we rub a smack. 

Small nerve fibers (pain receptors) and large nerve fibers (“normal” receptors) synapse on projection cells (P), which go up the spinothalamic tract to the brain, and inhibitory interneurons (I) within the dorsal horn. 

The interplay among these connections determines when painful stimuli go to the brain: 

1. When no input comes in, the inhibitory neuron prevents the projection neuron from sending signals to the brain (gate is closed).
2. Normal somatosensory input happens when there is more large-fiber stimulation (or only large-fiber stimulation). Both the inhibitory neuron and the projection neuron are stimulated, but the inhibitory neuron prevents the projection neuron from sending signals to the brain (gate is closed).
3. Nociception (pain reception) happens when there is more small-fiber stimulation or only small-fiber stimulation. This inactivates the inhibitory neuron, and the projection neuron sends signals to the brain informing it of pain (gate is open).

Descending pathways from the brain close the gate by inhibiting the projector neurons and diminishing pain perception. 

This theory doesn’t tell us everything about pain perception, but it does explain some things. If you rub or shake your hand after you bang your finger, you stimulate normal somatosensory input to the projector neurons. This opens the gate and reduces the perception of pain. 

Blocking pain or closing the pain gate is central to pain management. It is said that it is the chemicals, described above, which block pain also help to produce the joggers’ ‘high’ or that special serene feeling which occurs after lovemaking (which can send some people to sleep). 

Increasing your control over your pain
The first way to take control over your pain is to tell yourself your pain is something you can learn to manage. We do not aim to get rid of pain here, but to teach you how to manage it and keep the pain gate closed as much as possible. We can block pain signals in many ways. The main ones you will be taught here are relaxation, pacing and exercise. 

If you can learn to manage your pain you are on your way to rehabilitating to the best of your ability (this will be different for everyone). 

Begin now by continuously reminding yourself that your pain does not mean you are in imminent danger. 

Remember learning to control your pain takes Practice Patience, and Prioritizing. Remember too that all new learning takes time.
 

A Summary: Chronic Pain
Over time, chronic pain can get you into habits which may aggravate your pain e.g. tension, low mood and inactivity. Such habits become part of a vicious cycle which feeds the pain and keeps it central in your life.Below are same suggestions for outwitting the pain and ettseffing up positive cycles instead, which put the pain back in its place and you back in control of your life and your choices.