Many people think that mental and physical stress is an ailment only of modern civilisation but that is completely wrong. Stress has been a part of the human condition since humanity first walked the earth and is an important part of human survival. It is an active force that helps us to to meet whatever challenges that everyday life gives us and and we thrive at taking up these challenges, meeting the deadline and adapting to difficult situations.

How our bodies respond to stress was first described in the 1930's by two American doctors called Walter B Cannon and Hans Selye. They found that the first reaction to severe stress is what is known as the 'fight or flight' response, which activates the body's protective mechanism either to fight (confront the stressor) or flee (act to avoid the stressor or threat of it). Initially, the fight-or-flight response alerts us to danger and is, in fact, beneficial. It provides the strength, speed and stamina that is necessary survival.

The stress response is controlled by the endocrine system, which replaces various bodily functions, including the reproductive system, the immune system, growth, metabolism, allergic response and stress tolerance. Any unusual demand on the body's physical and mental resources stimulates the endocrine glands - mainly the adrenal, pituitary and hypothalamus - to secrete chemical messengers, called hormones into the blood stream. These stress hormones include powerful stimulants, such as adrenaline, noradrenaline, cortisol. Testosterone and thyroxin, which provide a variety of physical responses. The most common include increased pupil dilation, increased heart rate and blood pressure, muscle tenseness, increased blood sugar, fats and cholesterol and rapid breathing.

Unfortunately, although this natural physical response would have been invaluable at an earlier stage in human evolution, fighting and running away are rarely the correct responses to stressful situations in the modern world. Under long term, unrelieved stress our bodies remain in a constant state of arousal, which can result in the gradual onset of various health problems.

Primitive human beings frequently faced life and death situations, when alertness, strength, speed and performance were vital and the primary, instinctive response was to survive. The types of challenges that we all meet with today, however, are much different and as they they rarely require a physical response, the body's reaction to the situation is often inappropriate.

The stresses of modern life are more complex and last over longer periods of time. In the past, challenges were instantaneous and had to be resolved instinctively. Today, we are subjected to long term emotional, occupational and environmental anxieties, which demand that we maintain a certain level of mental and physical health. We also have to prepare ourselves for times of crisis and events that test us to our fullest, such as divorce, redundancy, bereavement or illness. This means that we have to be ready to 'fight or flight' at another level and in a completely different way from our forbears.

The rapid way in which our society now changes and constantly creates new challenges, places an unhealthy strain on a system that may be struggling to keep up. The extra mental exertion we all expend to keep - 'on top of things' can create a bottleneck of energy as pressure builds up with nowhere to go. If nothing is done to relieve the situation the mechanisms that we have for dealing with stress will eventually fail us, causing exhaustion and illness. It is vital therefore that we make a priority of finding ways of easing our bodies and minds out of 'fight or flight' mode. This will put ourselves on a better footing to be able to deal with the ever changing pressure of the modern world.

In order to do this we need a greater understanding and awareness of how our bodies work. Our automatic physical response to danger or stress involves a complicated chain reaction of bodily and biochemical effects, involving the brain, the nervous system and hormones. As soon as we perceive a threat, our body erupts with energy and strength and thousands of messenger hormones flood into the bloodstream. Our minds and bodies instantly become clear and alert and ready to deal with the threat. In this situation the main players are the brain, nervous system, lungs, muscle systems and hormones. Arousal is initially initiated by the hypothalamus which controls all automatic bodily functions and reactions; it releases chemicals called endorphins, which act as natural painkillers. They reduce the perception of pain and mental confusion and help us to deal with the situation by blocking out factors that may otherwise prevent us from giving less than our maximum performance.

Adrenaline helps by causing a quickening of the heart rate, a raising of blood pressure and a release of vital nutrients. It also creates muscle tension and effects breathing patterns, making them faster and shallower. However it is only one of the arousal hormones released by the adrenal glands near the kidneys. Noradrenaline, which is associated with positive ecstatic arousal, is al;so released into the bloodstream. The hormone cortisol is the agent involved in the conversion of glucose, stored in the liver, into blood sugar, creating instant energy and alerting the brain. The required surge of strength and effort comes from the male hormone testosterone. The thyroid gland also plays a part in the body's arousal response by releasing thyroxin, a hormone that stimulates the metabolic system, increasing its work rate and regulating oxygen consumption. This is very important as the body knows that it will need increased resources of energy. Our digestive system also slows down during this process, as blood is diverted from the skin and stomach. We automatically shut down the less necessary systems in order to concentrate on prioritising those that are necessary for our survival. As the digestive system is not regarded as essential in a life or death situation it slows down and is effectively put on hold.

The body has evolved an efficient and prompt survival response but as already mentioned, the things that cause stress today are more complex and require more sophisticated solutions over a longer period of time. Our hormonal system suffers if it stays in 'fight' mode as lengthy periods in this mode, are not healthy for our mental or physical well being. What starts as a positive range of responses can ultimately have a negative effect on our health and well being.

Research shows that we put our bodies on a challenge alert without realising it. Emotions such as anger, anxiety and impatience will produce the same chemical reactions in the body as standing in front of a charging elephant. The same physiology that leaves us feeling poised and alert can create problems over a long period of time. A build up of energy can lead us to become stress addicts, who become reliant on the adrenaline rush that stressful situations create.

An overdose of adrenalin is likely to result in irritability and agitation whilst too much noradrenaline can leave us feeling as if we are high on drugs. If arousal continues, the adrenaline glands create anti inflammatory chemicals to speed tissue repair but cortisol will also suppress the immune system, leaving it vulnerable to illness and disease. Extra sodium is retained, endangering the the performance of the cardiovascular system by causing fluid retention, raising the heart rate, increasing blood pressure and the possibly blood clots. Stomach ulcers are a classic symptom of stress, as the stomach cannot deal with the extra secretion of acid that occurs during stressful periods. Acute and cumulative stress over a period of time can even cause death.