In one study, which examined the medial articular nerve of the cat, it was demonstrated that 21 percent of the fibers were of the A-delta variety and 70 percent were C fibers. We can no longer avoid it. Consider some of the nociceptive processes chiropractors encounter on a daily basis. It is well known that nociceptors themselves and nociceptive activities in the spinal cord can become sensitized. However, the presence of chemical irritants, which are released after tissue injury, can lower nociceptor thresholds.
Peripheral sensitization refers to the lowering of a normally high nociceptor threshold.
Now innocuous stimuli, such as turning the head, bending over, and gentle palpation can activate nociceptors. It happens all the time. 19 Central sensitization is more difficult to describe than peripheral sensitization. First, it should be understood that central facilitation and wind-up are generally considered to be synonyms of central sensitization. It is now believed that neuronal plasticity is the process which creates central sensitization.