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Multiple Sclerosis 101: Understanding the Nervous System

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By Stephanie Butler, RN, MSCNSeptember 17, 2014

I have a theory that education leads to empowerment, and empowerment leads to people being good advocates for themselves and improved health overall. It can be difficult for healthcare providers to explain really complicated diseases, such as multiple sclerosis, during office visits. There is so much to cover in such a short time, that often education is minimized or cut out altogether in order to make sure that we have plenty of time to address other issues during the office visit. My first reaction to being diagnosed with MS was to go on an information binge, and learn everything I possibly could. I had the advantage of already being a neurosurgical nurse, and of having nearly a decade of training and education in human biology, anatomy, physiology, and pathology. However, the average person diagnosed with a serious neurological disease doesn’t have a background in neurology. I can’t imagine how difficult it would be to try to understand it all on your own, without any prior knowledge. After all, even some of the nurses and doctors I know recoil at the thought of neurology because it is a difficult topic to learn and master. However, I have confidence that you all will be naturals since you live these concepts every single day. Firsthand experience is always the best way to learn! So, I want to attempt to teach you the major concepts of neurology, with the hope that you will get a deeper understanding about what MS is and how it affects you. If you’ve ever had a symptom and wondered “what in the world was that?”, then this is for you!

First, the Basics

What exactly is the nervous system and what does it do?

The nervous system is divided into two parts, the central nervous system (CNS), and the peripheral nervous system (PNS). It is easiest to picture the nervous system as a tree. The CNS is the tree’s roots and truck, consisting of the brain and the spinal cord and the PNS is the tree’s branches, consisting of nerves that travel to our organs, glands, muscles, and skin.

Overall, the main job of the nervous system is to organize and keep all the cells in your body on task. It acts as the body’s drill sergeant and leader. Since the brain can’t scoop up a megaphone and yell marching orders, it communicates with it’s army of cells via electrical and chemical signals. These signals travel from the nervous system through nerves and down to cells until the command is carried out.

The nervous system never sleeps, and is constantly gathering information and reacting to it at an astonishing speed. For example, when your stomach is empty it sends a signal that your brain recognizes as hunger, and you become aware that you need to eat something. Some signals are automatically detected and responded to, without you even having to think about them. These are known as reflexes. An example would be when you touch a hot stove the sensation travels up your nerves and into your spinal cord. This triggers an instant response, and your muscles quickly jerk your hand away. Your brain simultaneously processes the incident which makes you say “ouch, that was hot!”.

Every task our body does, consciously or unconsciously, has to travel through the nervous system in order to be completed. This information is usually communicated so quickly that we don’t even realize how complicated of a process it is.

The PNS is made up of sensory nerves and motor nerves. Sensory nerves do exactly what they are named for! They sense what is going on in the body by gathering information from our skin, muscles, bones, joints, and organs such as the bladder, stomach, and lungs. They then take this information and send it to the CNS for processing and further commands. Once commands are issued by the CNS, it is the job of the motor nerves to carry out these orders. This is the basic principle behind all of our body’s voluntary functions, and it is also where communication breaks down and problems start to occur in people with MS. Bladder dysfunction is a perfect example. Sensory nerves sometimes “over-sense” and signal our brain that our bladder is full long before it really is, and the result is an overactive bladder that constantly gives you the urge to urinate. In others the nerves “under-sense” and fail to alert your brain that your bladder is full, and can result in leaking of urine or incontinence. Motor nerves can affect the bladder too. Since the bladder is a muscle, and we depend on muscles to hold in urine, muscle weakness can cause incontinence. Additionally, leg weakness can make it difficult to make it to the bathroom.

And that’s really the basics, not so bad right? Now if you are feeling brave lets move onto:

Everything You Need to Know about Nerves!

As you may have gathered already, nerves are responsible for carrying signals between the CNS and the PNS. Going back to the tree metaphor, the nerves are what carries water from the ground through the tree’s roots and trunk, and into the branches resulting in nice green leaves. Now replace “water” with chemical and electrical signals, and you’ve pretty much got it down! MS targets our nerves, so it is important to understand how they work if you want to understand MS.

Lucky for us, all normal nerves have three things in common:

#1. They are excitable! They’re like that lady at the nail salon who knows everything about everyone, and excitedly gossips to everyone who will listen. Sensory nerves recognize things like heat and hunger, and get so excited that they create an electrical current. This electrical signal quickly runs up a series of nerves to the CNS so action can be taken.

#2. The are conductive. An electrical cord’s job is to get electricity from a wall socket to a TV so that we can watch our favorite show. Similarly, a nerve must take electrical signals and conduct them from cell to cell in order to complete essential tasks like breathing, digesting food, moving our muscles, and keeping our heart beating.

#3. They release chemicals. Nerves are short, so it takes a chain of them to cover enough distance. This means that they must somehow get their electoral signal to the next nerve in order to keep the signal moving forward. They do this by releasing chemicals know as neurotransmitters. Neurotransmitters are able to jump across the gap between nerves and keep the electrical signal going. You may have heard of some common neurotransmitters such as seratonin and dopamine. I drew you a little picture so you can see how one nerve activates the next to form a chain reaction:


In the picture the yellow ovals are myelin. Myelin forms a protective coating that acts much like the rubber insulation around electrical wires. In the CNS myelin is made by a special type of cell called an oligodendrocyte. Oligodendrocytes produce myelin and wrap it around nerves so that they can properly conduct electrical signals. MS attacks both oligodendrocytes and myelin. This is a double whammy because it not only damages existing myelin, but also inhibits the production of new myelin.

Now how on earth does all of that relate to you exactly? Lets use the phone charger that my new kitten just chewed through as an example! I have to get rid of it, because it doesn’t charge my phone reliably anymore, and I don’t want to risk the fire hazard! MS is the same type of situation. The myelin coating is chewed through, leaving the inner wiring of the nerve exposed. Some electrical signals may go through, but overall the wire is frayed and unreliable. At least we don’t run the risk of spontaneously combusting (silver lining?)! Over time scar tissue forms around the damage (which is why the literal translation for MS is multiple scars). This scar tissue is what we can see in the form of lesions on an MRI scan.

Why MS Causes Such a Wide Variety of Symptoms

I have been trying to illustrate for you what a huge responsibility your nervous system has. It is responsible for organizing and carrying out thousands of tasks every day. In order to handle such an overwhelming job it has to take a “divide and conquer” type of approach. Each area of your brain is assigned a different task. There are areas for everything ranging from speech, memory, coordination, hearing, emotions and sleep, to bodily functions like bowel and bladder control, breathing, and digestion.

This is why MS, a disease that attacks the nervous system, can cause such a wide variety of problems. One doctor of mine once referred to MS as the whack-a-mole (fun game!) of diseases.  There is no way to know or to predict where a lesion is going to occur. For instance, one can pop up in your temporal lobe and cause you to start talking funny, or another could appear in your cervical spine and make your leg go numb. Some people have more lesions in their spine which primarily leads to issues with sensation, incontinence, and walking. Others have lesions in areas of the brain that make cognitive deficits their most challenging symptom. MRI’s allow us to look at the area of the brain that coordinates with the person’s symptom, so that we can monitor for any new damage.

When new symptoms occur, or when a relapse happens it means that the coordinating area is under attack. The nerves in that area have their electrical signals interrupted so they either have a more difficult time performing their normal duties, or they cannot perform them at all. Over time scar tissue forms and new research is showing that the nerves can even heal to some extent. The brain also finds ways to work around and compensate for the damage, so that some function can be restored. Much like building a bridge over a river, this process takes time and effort which is why it can take months to recover from a big relapse.

The majority of people living with relapsing-remitting MS have symptoms even in times of remission because our nervous system hasn’t completely compensated for past damage. Additionally, most of us have symptoms that wax and wane, which is what causes those “bad days” that we all know so well. There are several factors involved in these bad days including dehydration, lack of sleep, stress, extremes in temperatures, and illnesses. All of these things make it harder for even normal nerves to conduct electrical signals, and for nerves already damaged by MS it’s like adding insult to injury.

It’s pretty miraculous what our bodies go through, and all things considered they put up one heck of a fight. If you made it through this looooooong post without nodding off I hope you learned something new, and enjoyed it too! Any questions??

Profile photo of Stephanie Butler, RN, MSCN

Stephanie is a nurse, fitness enthusiast, science nerd, and eternal optimist. After being diagnosed with RRMS she realized that she could use her experiences as a patient to make a difference in the lives of others. Six months after she was diagnosed she became a Multiple Sclerosis Certified Nurse and began working in an MS center where she is a patient.

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