4: Increased Nervous System Arousal & Adrenaline The nervous system is the vast network of nerve cells specialised to carry information to and from all parts of the body to bring about bodily activity. The nervous system may be broadly divided into two parts: • the central nervous system: the brain and spinal cord that process information • the peripheral nervous system: the nerves that conduct impulses to and from organs, muscles and tissues At times of physical and mental exertion or stress the nervous system is automatically aroused or 'switched on' and the powerful hormone, adrenaline is produced. This prepares us for action and is known as the 'fight or flight' response. In CFS, the nervous system is frequently • • • • • • •
aroused in response to:
overwhelming daytime fatigue physical deconditioning frustration with a limited lifestyle fear about the symptoms scepticism of others sense of helplessness anxiety and uncertainty about the future
Being in a stressful situation and having CFS can lead to a further increase in nervous system arousal and production of adrenaline.
The effects of nervous system arousal and adrenaline on the body Nervous system arousal causes the body systems to work on 'maximum setting': 1.
Increased heart rate
The heart beats faster to pump blood to the muscles ready for action. Sometimes this is felt as palpitations, pounding or tightness in the chest (51). For some people this can be a frightening and distressing sensation causing further anxiety, which results in further nervous system arousal and release of adrenaline so maintaining the unpleasant physical sensations (52). In CFS, the heart is already deconditioned with a higher heart rate at rest, therefore, the further increase in heart rate during times of nervous system arousal can cause noticeable palpitations and increased fatigue. 2.
Increase in blood pressure
During exertion there is an increase in blood pressure that gives vital organs and muscles a better blood supply. At other times when physical and mental stress is not present, blood pressure on standing can be low (postural hypotension Chap 2). 23