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Nervous System

"It would seem that our glands effect control
far above proportion to their size and this is
true. It is also true, however, that the glands
have their master, probably the most remarkable
creation of life's miracles - the human brain."
(Dr Bernard Jenson PhD)

When trying to understand stress, anxiety and depression it can help to have a very basic idea of how our nervous system functions and the role it plays in the stress response; this will help us to understand our psychological health problems more clearly.

The human nervous system is very complex, but basically it is like a telephone network, the main switchboard is the brain, with telephone cables (nerves) running from it down the spine connecting into every organ and system of the body. The nervous system communicates with the body in two ways - via chemicals called hormones and by electrical impulses that travel at a speed of 130 metres per second.

The nervous system is broken down into 2 major parts:

1. The Central Nervous System consisting of the brain and spinal cord.

2. The Peripheral Nervous System.

The peripheral nervous system further divides into the autonomic nervous system which is the part we are particularly interested in with regard to stress, anxiety, depression and its related problems.


The function of the autonomic nervous system is to run all the automatic functions of the body like breathing, heart rate, digestion, endocrine (hormonal) system, etc.

The autonomic nervous system is divided into 2 divisions:

1. The Sympathetic Nervous System which initiates the stress response.

2. The Parasympathetic Nervous System which induces the relaxation response.

The body's organs and systems are supplied by nerves from the sympathetic and parasympathetic nervous systems which can slow them down or speed them up via hormones and electrical impulses depending on the situation.

Normally there is a balance kept between the sympathetic and parasympathetic nervous systems, but in long term chronic stress this balance can be disturbed and either one of the sympathetic or parasympathetic nervous systems can predominate over the other leading to stress related health problems.


When we perceive a real or imagined threatening stressor, the brain initiates the stress response by triggering a series of chemical chain-reactions that prepare the body for fight or flight. This reaction is a healthy, vital defense mechanism and triggers the release of hormones that affect every organ and system of the body. The hypothalamus, a collection of tissues in the brain, which then stimulates the pituatary gland in the brain which then stimulates the adrenal gland on top of each kidney to release its stress hormones. The stress response is the biological equivalent of a super charger on an engine.

The stress response hormones cause a number of biochemical and physiological changes which in the short term are vital and healthy but if the stressor is chronic then these stress hormones can start to undermine our health. Our stress response is designed to be triggered mainly in the short term.

In the long term these hormones cause blood clotting to increase and blood cholesterol levels to elevate increasing the risk of many diseases such as heart disease, stroke and angina. Stress hormones also weaken the immune system in the long term leaving us more vulnerable to infections. Increases in blood pressure are another long term effect of these stress hormones increasing the risk of stroke, heart attack and kidney disease. Chronically tensed muscles brought about by the stress response can lead to pain in the neck and back for example.

Excess cortisol in the blood interferes with mood enhancing neurotransmitters called serotonin. Disturbances in serotonin levels can be a factor in causing clinical depression and anxiety disorders as well as being linked to insomnia, obesity and increased sensitivity to pain.

Fortunately, the body has a compensating system which switches off the stress resopnse and releases chemicals that reduce blood clotting, reduce blood fats, lower blood pressure and heart and breathing rates.


The human brain weighs approximately 2 lbs, and it is 2 lbs of the most complex software on earth. It is so sophisticated it makes the most ultra modern super-computer look like an abacus in comparison. In the book, "The Healing Brain", Dr Robert Ornstein said we should see the brain not solely as an organ of rational thought but also as a gland. The brain is not just an organ used for thinking, it is a vast chemical manufacturing complex, producing many potent hormones called neurotransmitters which can have powerful effects on our psychological and physiological health.

Certain brain neurotransmitters have antidepressant and anti-anxiety effects and regulate appetite. Research indicates the balance of neurotransiiters affect everything from sleeping, waking, love, stress, anger, opetimism, pessimism, risk taking behaviour, aggression, drug abuse, alcohbol abuse, violence, anxiety, appetite etc.

Neurotransmitters are very powerful hormones that are secreted by the brain and nervous system and have a powerful effect on our psychological and physical health. To date more than 60 different neurotransmitters have been found and there are more to be discovered. These chemicals such as serotonin, adrenaline, noradrenaline, endorphins, dopamine, enkephalins etc., have a very powerful influence on our mood and to a degree on the way we think.

Research has indicated that our thoughts can influence these neurotransmitters in the brain. Serotonin for example, is positively enhanced by factors like healthy diet, laughter, exercise, but chronic stress can lower serotonin levels. Here then we can see biological and psychological factors at work influencing, among many other things, our mood.


Research on patient's brains scanned by Positron Emmision Tomography have indicated that the type of thoughts we have infleunce the balance of brain chemicals, so by learning to think more positively and realistically we can influence brain chemistry in a positive way, but other factors like an unloved, unsupported childhood can influence brain chemistry and physiology in such a way that it makes us less able to cope with stress in adulthood. If we think mainly negatively our brains secrete chemicals that can undermine our psychological and physiological health, whereas if we think more positively we can cause chemicals to be secreted that boost our psychological and physical health.

We also need to be aware that we are not exact carbon copies of each other, we have subtle biochemical and physiological differences that partially influence how we react to stress. For example each person's nervous system can react quite differently to any given stimuli or situation. Some people's nervous systems are more sensitive than others, more easily triggered by stress, and may also take longer to switch on the relaxation mode, once the stress response has done its job . There can also be differences in the amount of stress hormones we secrete in response to a stressor. People who have more of a tendency to being what is known as Type A personality are more reactive to stress and can produce up to forty times more cortisol (a stress hormone), they can produce four times as much adrenalin (another stress hromone),and also pump three times more blood to their muscles than the more laid back Type B personality.

This does not mean however that there is nothing that the more biologically reactive Type A's can do to reduce their stress. Research on Type A personalities who had suffered a heart attack showed that if they were taught stress management techniques then they could dramatically reduce their risk of a second heart attack when compared to Type A personalities who had not been taught stress management techniques.


Our genes can also influence our brain biochemistry as can caffeine, alcohol, diet, exercise and stress. These factors can all have an impact in a positive or negative way on our brain chemistry and make us more vulnerable to developing stress, anxiety, depression, insomnia, etc.


Depression and anxiety, Pre Menstural Syndrome, social phobia, anxiety, aggression, obsessive compulsive disorder, post traumatic stress disorder, violence, gambling, overeating, excess sex, drug abuse, have all been partly linked to low levels of neurotransmitters among other factors. Some people believe that those who participate in these risky behaviours do so because they want to and while this may be partly correct, the reason they are doing this is because it makes them feel better by boosting mood enhancing neurotransmitters which they may be low in, such as serotonin. It has been found that when, for example, an alcoholic's serotonin is boosted they loose the desire to drink in excess. This is how antidepressant drugs like Prozac work - they increase levels of serotonin which boosts mood and resolves depression.

This is a very basic explaination of how the nervous system works.


1. Cooper K. (1995), Understanding Hypertension, Bantam Books.

2. McCance K.L. (1998) Pathophysiology, The Biological Basis for Disease in Adults and Children, 3rd Ed. Mosby.

3. Noback C.R, Demarest R.J. (1986) The Nervous System, Introduction and Review, McCraw Hill.

4. Ornstein R, Sobel D (1987) The Healing Brain, Simon and Schuster.

5. Pert C (1997) Molecules of Emotion, Simon and Schuster.

6. Peterson C (1996) The Psychology of Abnormality, Harcourt Brace.

7. Sarafino E.P. (1998) Health Psychology, 3rd Ed. John Wiley and Sons.

8. Watson D (1995) A Dictionary of Mind and Body, Andre Deutche.

9. Woolpert L (1999) Malignant Sadness, The Anatomy of Depression, Faber and Faber.