Together, the brain and nervous system are responsible for processing and storing information, thinking, sleeping, perceiving pain, breathing, contracting muscles, glandular secretions, maintaining body temperature and more. In short, they provide a vital communication link between our internal and external worlds. This happens because the sensory organs of the nervous system receive external information and relay it to the brain.

The nervous system has two parts, the central and the peripheral systems. The central system consists of the brain and spinal cord, both made up of nerve fibres. The peripheral system is the network of nerves located throughout the body.

The brain has three main parts: the cerebrum, cerebellum and brain stem. The cerebrum receives information, thinks about it, processes it and then sends it out. The cerebellum is essential for balance and coordination. The brain stem connects the cerebrum to the spinal cord and is responsible for regulating such functions as respiration, heart rate and blood flow, eye movements and pupil size, neck and head movement.

The peripheral system penetrates every tissue of the body just as the circulatory system does. It is composed of 28 billion neurons, or nerve cells that transmit messages by means of electrical impulses, or signals, to organs. When the impulses arrive at an 'end organ' or effector, they cause activity. If the effector is a muscle, the activity is contraction. But if it is a gland cluster connected with the digestive tract, the action is the release of digestive enzymes.

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 the body, the nervous system also influences how it acts or reacts to stress. The fight or flight response is a good example. This is a hormonally stimulated state that prepares the body for an upcoming challenge.

Stress is a factor in every life, and the degree to which it affects us negatively is largely determined by how we react to stimuli around us. We need to supply the nervous system with good food so that our nerves can accurately communicate and handle the various stresses to which they are constantly exposed. Even though everyday hassles may seem minor, researcher Dr. Richard Lazarus has found that in combination they can have an even bigger impact on our health than traumatic events such as death, major illness or financial difficulties.

It seems our nervous system doesn't differentiate between a physical threat and an emotional one. Thus, crying children, 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, and may even evoke our fight-or-flight response. This defence mechanism can actually damage our health if it is evoked constantly and unnecessarily and the energy released by it is not dispelled through fighting or fleeing.

Prolonged emotional stress can lead to a breakdown of health. Evidence shows that many of us may not be handling stress well. In fact, it has been estimated that half of those going to see a doctor have symptoms 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.

Psychologist Donald A. Tubesing related stress to the tension on a violin string. He said we need "enough tension to make music but not so much that it snaps".

Fortunately, stress can be managed and its effects reduced. Exercise, meditation and relaxation techniques, attitude changes and improved nutrition are some effective ways to handle it.

Stress can also increase the need for certain nutrients since it alters our metabolic process. For example, an increased metabolic rate means an increase in the burning of carbohydrates. When larger than normal amounts of carbohydrates are metabolised, the need for thiamine and other members of the B-complex family may increase.

Stress is closely related to nutrition. The fight-or-flight response increases the metabolic process, which in turn increases the need for certain vitamins, particularly the water-soluble vitamins that must be replenished on a daily basis. This is why the B-complex and C vitamins are the core of all anti-stress vitamin supplements.