The Nervous System How it Works

Editor's Note: When you see these three dots surrounded by a gray rectangle — 1 — you can click on it to get further information about the topic. Click a second time, and the message goes away.

The Nervous System: What is it?

The nervous system is defined as "the network of nerve cells and fibers that transmits nerve impulses between parts of the body." But that limited definition hardly explains its many parts and purposes.

To go further: "The nervous system is the part of our body that coordinates voluntary and involuntary actions and transmits signals to and from different parts of our body." Now we're looking at a much more complex definition than just a "network of nerve cells."

Once you know that the brain is a part of the central nervous system, you know that it is indeed complex but absolutely necessary for our survival.

As well, it's important to know that there are two parts:

What are the parts of the central nervous system?

The brain is an important part of the Central Nervous System.

The central nervous system processes all information coming from and going to the peripheral nervous system.

The brain and spinal cord are the two main organs of this system, and they work together: (1) the brain processes and interprets sensory information sent from the spinal cord, and (2) the spinal cord sends on the information to the peripheral nervous system.

Both the brain and the spinal cord are protected by three layers of connective tissue.

The brain, the control center, has three parts:

The spinal cord is shaped like a cylinder. It runs down the center of the spinal column extending from the neck to the lower back. Spinal cord nerves send information from body organs and external stimuli to the brain (ascending) — and they also send information pertaining to motor function from the brain to the body (descending).

Finally, none of this could work without neurons which are the basic unit of the nervous system. Neurons are classified as:

What are the parts of the peripheral nervous system?

The peripheral nervous system consists of the nerves and ganglia on the outside of the brain and spinal cord. It has two parts: The Sensory-Somatic Nervous System and the Autonomic Nervous System.

The Sensory-Somatic Nervous System consists of sensory nerves and somatic nerves.

In the head and neck, twelve cranial nerves (ten of which originate from the brainstem) carry somatosensory data and mainly control the functions of the anatomic structures of the head. This includes the olfactory nerve and the optic nerves.

For the rest of the body, spinal nerves are responsible for somatosensory information. These arise from the spinal cord and control the functions of the rest of the body. In humans, there are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal.

The autonomic nervous system controls involuntary responses to regulate physiological functions. This includes:

The autonomic nervous system is always activated, although, depending on the situation, one state can overshadow the other, resulting in a release of different kinds of neurotransmitters.

What are some of the disorders of the nervous system?

Disorders of the nervous system may involve the following:

Can exercise help the nervous system?

Regular exercise decreases activity in your sympathetic system and increases activity in another part of the autonomic nervous system called the parasympathetic nervous system.

When you're confronted with stressful situations, involuntary processes in your body increase your blood pressure and heart rate and decrease food digestion. In today's society, it is believed that constant triggering of the sympathetic system may play a significant role in developing heart disease. There is reason to believe through research that If you lead an inactive lifestyle, your heart rate and blood pressure may be frequently higher than it should be, increasing your risk of heart disease. 2

When you engage in regular aerobic exercise, however, you reduce the stress load on your body, improving your blood flow and heart function. In combination, these physical changes lead to reduced activity in your sympathetic nervous system and increased activity in your parasympathetic system (see sidebar). 3

"The exercise-related reduction in the activity of your sympathetic nervous system may significantly decrease your chances for developing heart disease," according to Patrick J. Mueller of the University of Missouri-Columbia. "Increased activity in your parasympathetic nervous system may also contribute to decreased heart-health risks. Additionally, it appears that the more you exercise, the greater the effects on your sympathetic and parasympathetic systems. However, further study and testing are needed to verify the real-world results of laboratory testing." 4

So, once again, we can find evidence that exercise is good for you!

Some other articles which might be of interest to you:

I am a BCRPA-certified fitness instructor in Vancouver, BC. I teach four classes at the West End Community Centre in Vancouver, BC, mostly designed for the older adult. The Inevitable Disclaimer: Everything published here expresses only my opinion, based on my training and research. What you do with the information is entirely your own responsibility. I am not liable for any injury you suffer that seems to be related to anything you read here. Always consult your doctor before beginning an exercise program. For other articles, return to the table of contents.

★ ★ ★

  1. These three dots behave exactly like a footnote. Click on them and you will get more information about the topic. 

  2. From the LiveStrong website, an article titled: How Does Exercise Increase Sympathetic Nervous System Activity? 

  3. From the LiveStrong website, an article titled: How Does Exercise Increase Sympathetic Nervous System Activity? 

  4. From the LiveStrong website, an article titled: How Does Exercise Increase Sympathetic Nervous System Activity?