Nervous System Basics

Hey everyone,

As you may have heard me say, I really feel that people living with chronic pain/fibromyalgia can benefit immensely from learning about how the body works. Even the feeling that you are just beginning to understand the complex processes making up your experience of pain can help give you a sense of control over things.

And reading about the new research that is being done on pain, even if you don’t completely understand every word, can sometimes give you a reason to remain hopeful at times when you’re feeling stuck.

With that in mind, I’m going to back way up and publish a post I’ve been meaning to write for a very long time.  Here I’ll outline a few key terms and concepts about how the nervous system works. Hopefully it will be helpful to anyone who is interested in learning more about pain.

So let’s get started.

The nervous system can be divided into two main branches.

The central nervous system consists of the brain and spinal cord, and is shown in pink in the diagram above.

The peripheral nervous system consists of all the nerves in the body, and is shown in yellow.

The brain is the command center for your body, and it is where your experience of pain is processed. It is where you think consciously, but it also controls many unconscious functions, such as breathing, your sense of balance, and the ability to orient your body in space.

The spinal cord is the relay system for messages between the brain and the peripheral nerves. (It can also play a role in affecting how strong your ultimate experience of pain is, but we’ll talk more about that later).

The peripheral nerves have two main jobs:

Sensory: Sensory nerves send signals to the central nervous system about what you are feeling physically. When you stub your toe or get a papercut, it’s sensory nerves that send that signal up your spinal cord to your brain.

Motor: This is (to me) a kind of funny scientific word. It really just means “movement.” The motor nerves of the peripheral nervous system are what tell your muscles to move, as well as tell your organs to perform specific functions.

Pain

When people talk about how pain works, they are generally talking about the relationship between the sensory nerves, the spinal cord, and the brain. The sensory nerves send signals up to the brain about any damage that may have occurred, and the brain decides how to interpret those signals.

But Pain is a Two-Way Street

Historically, people considered this pain pathway to be a very consistent, cut-and-dry system that always worked the same way every time. If a person was in a lot of pain, they had to have a lot of physical damage/injury. If they weren’t in very much pain, they must not have a very serious physical problem.

However, scientific advances in the past few decades have shown that pain is actually much more complicated than that. It turns out that the severity of a person’s pain does not always reflect accurately the amount of physical injury they have experienced.

You can have soldiers in battle who do not even realize they’ve been shot– their peripheral nerves are sending very strong messages of “damage” up to their brains, but their brains tune those signals out because they need to focus on survival.

Conversely, you can have people with chronic pain, who– due to a number of potential factors—can experience excruciating pain in response to a very minor injury, or in fact no injury at all.

Central Sensitization

At the risk of boring my long-time readers, let me define one of my most favorite terms again.  Central sensitization is the process responsible for this last phenomenon, where people can develop an increased sensitivity to pain.

The term refers to a series of changes that can take place in the central nervous system (the brain and the spinal cord) which can ultimately make a person much more sensitive to pain.  In some cases, central sensitization can become a self-perpetuating phenomenon, in which a person continues to feel pain long after their initial injury has healed.

Central sensitization is such a fascinating topic.  There is still much research to be done on it, but so far it is believed to play a role in such seemingly-diverse conditions as fibromyalgia, chronic fatigue syndrome, irritable bowel syndrome, temporomandibular disorder, and many others.

One Last Thing

When I first started trying to understand the amazing, interesting new research that’s being done in pain, I kept hitting this one term that mystified me.  The dorsal horn.  What the heck is a dorsal horn?  I was so confused by this for a long time, and it really held me back from understanding a lot of articles.

Turns out, the term dorsal horn refers to an area in the back of the spinal cord.  The back of the spinal cord is where the sensory nerves meet with the spinal cord, so their messages can continue on up to the brain.  It’s pretty simple actually– the sensory nerves connect with the back of the spinal cord, and motor nerves connect in the front.  So when people talk about the dorsal horn, they are  talking about where sensory information is entering the spinal cord and then being relayed on up to the brain.

For more info

If you want a really great overview of the divisions of the nervous system, I highly recommend this video.

Conclusion

I really hope you’ve enjoyed this post!  As you can see, it’s written in a very different tone, and for a very different target audience, than my previous post.  I’m still in the process of figuring out what type of post works best on this blog.  I really want to be able to write about advanced scientific concepts for every day people, and I’ll probably be trying to figure out the best way to do that for a while. Your thoughts/comments/suggestions are always welcome, so please let me know if you have any! Thanks!

Part Two: click here if you’d like to keep reading!

Top photo courtesy of Geralt