TRI-4, Wk9, Day 238 - Monday

Week 9?! How the heck did that happen??? Neuromuscularskeletal Diagnosis (NMS) class was understandable but complex today. If there was ever a time to review notes for a class then today's class would have been it. I'll try to do that here.

In our homes we have different kinds of wired connections. We may have 110v wires for a lamp, 220v wiring for a refrigerator and a coaxial cable for an internet connection. In the same way we have different kinds of nerve fibers running throughout our body. In NMS today, we focused on pain. There is an A-delta fiber in our body which is used to conduct sharp, localized pain and we also have a "C" fiber used to conduct a more diffuse type of chronic pain. We talked about the C fiber today and how it conducts pain. Detecting pain is also known as "nociception".

The initial cause of the pain may be chemical, mechanical (aka tactile) or thermal (aka heat). A very interesting aspect we talked about was at the junction from one C pain fiber to the next. A substance known as Glutamate is always being released from the terminal end of one pain fiber to the next pain fiber which eventually leads to the brain for interpretation. Released glutamate finds receptors called AMPA which stands for alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate ....so....we'll just stick with AMPA.

Now, when we have "real" pain - or I'd hasten to guess a more intense level of pain then a threshold is crossed and the terminal end of our C pain fiber releases Substance-P which looks for NK-1 receptors. Those AMPA receptors are usually bound w/ Magnesium but when substance-P enters the picture and finds NK-1 receptors then the Magnesium leaves the AMPA which then allows Calcium to enter the nerve fiber. This causes the nerve to depolarize which then causes us to interpret pain.

With chronic pain, we have what is known as the "Wind Up Phenomenon" which means that pain receptor sites on our nerve cells will increase. With a greater number of receptors, less input will be needed to stimulate pain. We may call this sensitization hyperalgesia or even hyperasthesia.

I'm still trying to get a handle on all this but, from my current understanding, the substance-P also facilitates production of Nitric Oxide (NO) and prostiglandin-E2 (E2 for short) and an increase in NO and E2 causes a greater production of substance-P which is how that vicious cycle of pain sensitization occurs.

Now, what else happens as a result of excess substance-P? Well, there is something called NGF which stands for Nerve Growth Factor. At this point we have to realize something. Earlier, when I said the nerve route eventually gets to the brain where we interpret the signal as pain then we must be aware that the route to get to the brain is in our spinal cord. Specifically, there are tracts in our spinal cord and the route the pain takes is along tracts called Lamina 1 and 2. Also keep in mind that anything we perceive via our peripheral nervous system must travel via our spinal cord to get to our brain and there is a lot to be perceived! This Nerve Growth Factor (NGF) stimulates the growth of new nerve cells - ie, new axons to sprout from lamina 3 & 4!

Lamina 3 & 4 is where A-beta fibers travel. Those fibers carry mechanoreceptor impulses. Mechanoreception is basically movement of the body, sometimes referred to as proprioception and it's from the tracts occupied by those fibers which sprout the new nerve cells when eventually can end up connecting with the incoming pain fibers. This is where things get interesting because if the impulses from movement end up connecting with the incoming nerves for pain then simply moving may cause pain since those movement impulses are now also sending extra signals to the pain fibers. A result of the sprouting and new connections to pain fibers is known as Albdenia ...I probably don't have that word spelled correctly because I couldn't find anything on the internet on it - have to check my book...

The last part of the story here is how the body can help prevent these pain cycles, especially the new connections. For now, we've learned of 5 chemicals the body can send to the rescue. These 5 chemicals are

1. endorphins
2. enkephalin
3. nynorphin
4. GABA
5. Glycine

There is something known as the PeriAquaductal Gray (PAG) Area (I'm thinking this is somewhere in the brain) which makes endorphins which stimulates mu-opiate receptors - essentially, the endorphins help to block NMDA channels which helps to inhibit substance-P. Of course, one way the PAG is stimulated is by pain.... it's kind of like an on/off switch with regards to it's stimulation by pain.

What a minute ...notes update ....the PAG is part of the Decending Inhibitory Pathway (DIP) which...I guess is part of the brain... :)

Another part of the DIP is called the Nucleus Raphe Magnus (NRG) and that part of the DIP releases Enkephalin. This (as are the first three things in my list) is another opiate which can help reduce pain.

#3 on our list is Nynorphin which is released by an interneuron and is 10x more effective than morphine - everything shuts down (regarding pain) when nynorphin is released.

GABA - aka gamma-aminobutyric acid is something I've mentioned in previous blogs (we first learned about GABA in Tri-2) and is an inhibitory chemical.

Glycine is released by Renshaw cells which, I believe are in the spinal cord.

Anyway, all this stuff kind of gives a glimpse of some of the scientific theory behind chiropractic health care. These are some of the drugs that chiropractors work with, they aren't handed out by a pharmacist, they're made in our own bodies, they're made in the CNS, our brain & spine. It's like that function follows form principle wherein the shape of an object should be primarily based on its function or purpose. Chiropractors help people maintain the proper form of vertebrae so that nifty little spinal cord may continue to function as intended.

There's so much more to say about all that but I've got to wrap this up. A classic example of what's been talked about here may be fibromyalgia which used to be thought of as a hysterical kind of disease (it affects women about 7x more than men) In the 1970s valium was the standard Rx but more modern research indicates it's probably a problem with the central nervous system. SSRI's (selective serotonin reuptake inhibitors) now tend to be given as "treatment" for fibromyalgia. I put the word treatment in quotes because it's not a cure, the prescription doesn't fix the cause (as is the case with most medications) they're simply a management tool to help regulate symptoms. In the long run, SSRI's may do more harm than good and actually exacerbate the condition they were initially used to help.