Neuromechanics Weekly: Third Installment


The Pain Pathway

Pain is the emotional response to adequate activation of the nociceptive afferent system.


Pain is an emotional response. We feel (or experience) it in the cingulate gyrus (the gyrus right above the corpus callosum, that thing they cut in “One Flew Over the Cukoo’s Nest, see the 1st picture above). Your pain is different than your patients/clients pain. Like John Travolta said in Swordfish "It’s all about perception…”

Pain is subjective. Men usually have lower tolerance for physical pain than women (We think this has to do with their wiring, as it is all connected for them, and we males have our little boxes we keep everything in (see here if you don’t understand).

We know what “adequate activation” is. Enough stimulus to elicit a response. Like when someone keeps pestering you and finally you let them have it!

The “nociceptive afferent system” is the pain pathway. You remember: the C fibers (or pain fibers) in the periphery get activated (adequately, of course), the impulse travels up the peripheral nerve to the dorsal horn of the spinal cord, synapses in lamina 2-5 (the key here is that it synapses; proprioceptive and other sensory stimuli DO NOT synapse, but travel higher up the chain. The synapse allows modulation of the signal, the subject for the next in this series’s post). The next neuron in the pathway (remember, we are still in the cord, right after the 1st synapse) crosses (or decussates) the cord and travels up the ever famous lateral spinothalamic pathway (see middle picture above). We would think this pathway (from the name) goes an synapses at the thalamus next (THE central relay for ALL sensory stimuli EXCEPT SMELL); in reality only about 27% of the fibers synapse here, and then go to the parietal lobe. to tell you WHERE the pain is.

What about the other 73%? They go to the reticular formation ( a loosely organized group of nuclei in the brainstem) to cause the autonomic concomitants of pain (increased heart rate, increased breathing, nausea, urge to urinate, etc).

So, the next time someone has pain in their knee or foot, or _______, not only will you be able to tell what tissue is causing the pain, but now can trace the pathway north to the brain. Why is this important? Because of the modulation that YOU can influence with your therapy. More on that in  the next neuromechanics.

The Gait Guys. Eliciting a response in your cingulate gyrus. Hopefully, you are storing this in your inferior temporal gyrus (memory area) for future use.