Pain and Gate Control Theory

Pain is defined as an unpleasant sensory and emotional experince associated with, or resembling that associated with actual or potential tissue damage by IASP*. We are all experiencing [%95 of whole population] pain less or more and it is limiting our physical activities. We are classifying pain by duration, physiology, region or mechanism.

Pain, which usually tells us there is something wrong in our body, consist of 4 steps in nervous system.

Lets describe this pathway basically. Stimulations are perceived by specialist neurons called nociceptors and it process into electrical stimulation. This electrical stimulation gets along in nervous system and it changes a bit. Eventually, it is percieved by different central nervous system parts.

Wall and Melzack, described how emotion, thoughts and physical stimulators effect our pain perception by inhibations which occurs on pain pathways.

For instance, theory describes how athletes keep running despite the pain or how murderers keep run away from police officer despite the bullet pain.

Before inhibation mechanism, we need to know 3 types of neuron fibers. Pain is sensoring by myelinated (isolated) type A-delta and unmyelinated (unisolated) type C neurons. Third type of neuron that we need to know is A-beta. We need to know that, because it is a mechanoresceptor.

These neurons that we mentioned, encounter in the part called “substantia gelatinosa” of the region that we see in the form of a horn behind the cross section of the spinal cord. At substantia gelatinosa, A-beta fibers which are carrying mechanical stimulations are able to pass due to largeness of fiber, but the others which are carrying pain stimulations can not pass. Basically, a-beta fibers are closing gates to pain neurons.

Thanks to this gate, pain neurons can not pass to other parts of pathways and it cannot be perceived by parts of central nervous system. And we do not feel the pain. The reason of gate’s closing is gate’s sensibility to large fibers.

Activating gate cells and start inhibation is is the basis of many physical therapy and rehabilitation methods today.

*Melzack, R., & Wall, P. D. (1965). Pain mechanisms: a new theory. Science, 150(3699), 971-979.

Writer: F. Eren Oluc