Pain is a major force of survival. Without pain, we would, simply, not survive. Of course, pain can be cumbersome, and unnecessary, at times. For example, when you stub your toe on your desk, do you really need that much pain for that long?

More importantly to this discussion, what do you do when you stub your toe? Probably do a bit of hopping, and you certainly grab that toe and squeeze or rub it.

Why do you do that? The Gate Control Theory of Pain can answer that.

At its basic, the Gate Theory of Pain dictates that non-painful input (like that rubbing) closes the gates to painful input. This results in the prevention of the sensation of pain from being fully perceived by the brain. Simply, when the painful stimulus is overridden by a non-painful stimulus, the pain sensation does not travel to the central nervous system (CNS).

Even more simply, non-painful stimuli suppress pain.

Why is that?

Collaterals, or processes, of large sensory fibers that carry cutaneous (skin) sensory input activate inhibitory interneurons. Now, inhibitory interneurons do just what their name implies: they inhibit. And what do they inhibit in this case? Pain sensory pathways. This therefore modulates the transmission of pain information by pain fibers. Non-painful input suppresses pain by “closing the gate” to painful input.

This happens at the spinal cord level: non-painful stimulation will result in presynaptic inhibition on pain (nociceptive) fibers that synapse on nociceptive spinal neurons. This inhibition, which is presynaptic, will therefore block any incoming painful stimuli from reaching the CNS.

More on this topic on this week’s Séance Sunday, coming up!