Our nervous system can be compared to a city communication network that is linked to a central computer.  The computer relays signals from within the system, as well as from other cities.
In the same way our body's nervous system provides a vital communication link between our internal and external worlds.  The sense organs of the nervous system receive external information and relay it to the brain.  There it is sorted, prioritized, and passed to organs, tissues and cells so they can adapt to changes in both environments.
The nervous system is composed of two parts: the central and the peripheral system.  The central system is the brain and spinal cord, both made up of nerve fibers.   The peripheral system is the network of nerves throught the body.
The nervous system penetrates every tissue of the body, just as the circulatory system does.  It is composed of 28 billion neurons, or nerve cells.  These cells are our communication specialists and messages are transmitted by electrical signals.
All of our sensen - vision, hearing, smell, taste and touch - are a vital part of the nervous system network.  They rely upon mechanical, chemical and electrical processes in order to sense the body's condition and environment.  That information is then transmitted to the brain via nerve impulses.

The Communication Process

The nervous system communicates two basic types of messages: one is to activate, the other is to relax.  Some of its actions are automatic (i.e.,the heartbeat, breathing and digestion) and some are voluntary (i.e., eating, drinking and walking)
In addition to influencing the physical functions of our body, the nervous system also influences how we act or react to stress.  The fight or flight response is a good example.  This is a hormonally stimulated state to prepare the body for an upcoming challege.
Chemical reactions influence the heart, nervous system, muscles and other areas of the body.  We need to supply this system with good food so that our nerves can accurately communicate and handle the various stresses to which they are constantly exposed.

Our nervous system doesn't differentiate between a physical threat and an emotional threat.  Thus, screaming kids, a critical boss, unpaid bills, traffic jams, missed deadlines and a host of other mental/emotional crises can be perceived by our nervous system as a form of danger.  These situations can also evoke our fight/flight response.  This defense mechanism can damage our health when it is constantly evoked unnecesssarily and the energy released by it is not dispelled by fighting of fleeing.
Prolonged emotional stress can lead to a breakdown of health.  Evidence shows that we may not be doing so well in handling stress.  It has been estimated that one-half of those going to see a doctor have sysmptoms that can be traced to psychological stress.
Of course, emotional stress is not the only factor involved in illness and disease, nor is it necessarily the primary cause.  It is, however, one of the risk factors associated with poor health.