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The autonomic nervous system ( ANS ) as we have already seen is part of the peripheral nervous system ( PNS ).
It has an important function in maintaining the internal environment of the human body in a steady state. This role is vital in returning the body to a homeostatic state after trauma.
As various changes occur within the environment, both internal and external, the ANS reacts by regulating such things as the Blood Pressure, Heart Rate, Concentration of salts in the Blood Stream etc.
For example when the level of nutrients within the blood stream falls the Sensory Nervous System (SeNS ) picks this up and stimulates the ANS to activate food seeking behaviour and also stimulates the digestive processes. If the body becomes dehydrated such as playing football on a very hot cloudless day the SeNS will pick up sensory information on the depletion of body fluid and the ANS will activate the mechanisms which conserve and replenish body fluids.
The ANS is also involved in many other body activities such as, waste disposal, response to stress, and sexual response.
The functions of the ANS underlie the physiological aspects of coping during stress and forms a major link between the nervous system and the endocrine system during these times.
The system generally works automatically without voluntary control - hence the name which comes from ancient Greek meaning 'self governing'. We do not consciously direct the rate of our heart beating nor are we normally aware of the diameter of our blood vessels or the need to stimulate our salivary glands to produce saliva.
However the effects of the ANS do impinge upon our consciousness, especially at times of heightened emotion. For example most of us have experienced fear, either real or imagined, at some time in our lives and have been aware of our hearts beating faster. The increased heart rate is due to the effects of the ANS.
Once physiologists believed that the system was wholly independent of the CNS. However we now realise that this is not quite the picture and that there is some CNS component involved.
This includes the spinal cord, the brain stem and the hypothalamus. The hypothalamus is probably the most important area of the brain involved with the ANS but other areas such as the medulla oblongata and parts of the limbic system of the cerebral cortex have an important part to play.
This will be enlarged upon during the sessions on the CNS later in the course.
Some techniques such as Yoga or Transcendental Meditation claim that it is possible to gain conscious control over autonomic activities. Studies of people practising Transcendental Meditation have claimed that it is possible to gain conscious control over autonomic activities. Studies of people practising 'transcendental Meditation have indicated that physiological changes do occur. Heart beat, metabolic rate and blood pressure decrease and alpha- waves are shown to increase when brain activity is monitored by electroencephalogram ( EEC). The studies have also suggested that the body's response to noradrenaline ( sometimes known as norepinephrine ) is lowered. As we shall see later noradrenaline is a hormone important in autonomic response.
In recent years the technique of biofeedback has been developed in order to assist people in relaxation. This technique provides the individual with some recognisable indication of the status of an autonomic function. For example, by connect.ion to a digital readout or to a sound monitor etc. Using these readouts as a guide subjects have learned to actually exert some conscious control over such things as brain wave patterns, blood pressure, blood sugar levels etc, People have learned to prevent or reduce pain from problems such as pain from headaches. They have even been able modify abnormal heart rhythms. The technique has also been used in helping women relax during childbirth.
This page last updated Sunday, 02 May 1999 08:28 +0100
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