Now that we understand how these two receptors work it will be easier to discuss the neurological changes. When there is a hypomobile segment there is less mechanoreceptor activity because there isn't movement occuring. One of the functions of mechanoreceptors is to inhibit nociceptors, also known as the Melzack and Wall Gate Theory. This theory can be easily understood if you have ever hit your finger or hand and began waving it around or rubbing it after to make it feel better. By moving or rubbing your hand your engaging mechanoreceptors which in turn help to inhibit the sensation of pain. When there is a subluxation, there is decreased mechanoreceptor activity, which leads to loss of inhibition, and inevitably an increase in nociceptor activity secondary to cell damage.
The nociceptors then go on to fire signals onto interneurons which then can fire onto a number of different cells and have several different paths. If the signal ascends the spinal cord via the spinothalamic tract and reaches the thalamus, there will be a pain sensation. If the signal ascends but is inhibited prior to the thalamus, then no pain is felt (which is 90% of all signals sent via nociceptors). The signal may ascend but then synapse in the reticular formation, which is the area of the CNS that control autonomic responses (such as heart rate and blood pressure).
The interneurons can go on other paths as well. Another path they may take is to synapse on the anterior horn of the spinal cord. The research has shown that by having an increase in the number of synapses on the anterior horn results in increased local muscle tone, most noticiably in the intrinsic spinal muscles. Having hypertonic musculature further pertepuates the cylce of hypomobility.
Finally the interneurons can also fire onto the intermediolateral cell columns, which results in increased sympathetic nervous system activity.
So as the weather gets warmer and we begin our spring cleaning, don't forget to ignore your body. Those strained muscles will begin to tighten up causing trigger points and hypomobility. Come into the office and make sure that you body is f