Definition: Autonomic Nervous System (ANS)

The Autonomic Nervous System (ANS) is a major division of the human Nervous System (NS). The ANS controls the predominantly automatic and self-regulatory functions of our blood vessels, most of our internal organs, various tissues and our glands.

The ANS is in turn subdivided into two main areas:

• The Sympathetic Nervous System (SNS), the main function of which is concerned with arousal and brings about catabolic processes. The SNS becomes activated in response to a perceived threat or stress, sometimes switching on the 'fight / flight' reaction, which sends energy to our limbs for action and takes energy away from our digestive system. This is a primitive but entirely natural response that enables us to react quickly, for instance to jump out of the way of a bike that suddenly comes up onto the pavement next to us. However, the SNS can become over-active during periods of high or prolonged stress, often resulting in physiological and psychological strain or illness.

• The Parasympathetic Nervous System (PNS) is dominant during quiet, peaceful times and brings about anabolic processes. The PNS can become activated for instance, when a stressful situation ends, or the person uses a coping strategy in order to calm down. The PNS is predominantly involved with our digestive system and the conservation of energy, so when someone practices the Alexander Technique Lying Down Procedure, for instance, you will often hear a gentle tummy-rumble, which is a sound to be welcomed as it indicates that their nervous system is calming down and the PNS is activated, so their gut can function again.

These two divisions of the Autonomic Nervous System are mainly antagonistic, creating opposing reactions in our bodies. However the SNS and PNS do, for the most part, balance their functioning to bring about homoeostasis in our system. They also work together at times of strong emotions, such as during sexual activity or extreme fear.