Article: the fight or flight response

The autonomic nervous system functions automatically and below the level of consciousness to control such functions such as heart beat, breathing, digestion, pupil size, amount of blood in the arteries, etc. It has two parts, the sympathetic and parasympathetic they act in opposition to one another to create balance between energizing the body for activity and calming the body for relaxation. It consists of nerves and ganglia. The largest ganglia are the solar plexus this links the central nervous system with organs in the body.

When a person feels threatened in any way the body prepares for "fight or flight" i.e. the body prepares to give the individual extra energy, oxygen, improved vision, better blood supply to muscles by slowing down non-essential activity, increased awareness of all senses. This is so that the person can physically fight off the attack or run away.

However in most societies today many situations do not require us to physically fight or to run away. Our ancestors needed this in order to face physical danger, in most situations we do not. The process is triggered by our emotional response to a situation or by our higher senses i.e. smell, taste, touch / sensation, sight, hearing and the thoughts and judgements we attach to the stimulus. The nerve cells of the sympathetic nervous system in the hypothalamus and the medulla oblongata (in the brain) are stimulated. The hypothalamus increases secretion of adrenocorticotrophic hormone releasing factor (ACTH-RF) into the blood stream. This is received by the pituitary gland and stimulates increased production and secretion of adrenocorticotrophic hormone (ACTH) into the blood stream. When this reaches the cortex of the adrenal glands (situated on top of the kidneys) growth and activity of the cells increase the secretion of glucocorticoid hormones, primarily hydrocortisone (cortisol) into the blood stream. At the same time adrenaline is secreted from the medulla of the adrenal glands into the blood stream.

Together, increased sympathetic nervous activity, increased secretion of glucocorticoids and increased secretion of adrenaline bring about the following physical responses:

• The metabolism speeds up releasing nutrients, including glucose, there is an increase in cholesterol in the blood stream.
• Heart rate increases to provide more blood
• Respiration increases, promoting oxygen supply to the tissues and the removal of carbon dioxide
• The supply of blood to and from the tissues is increased
• Blood is redistributed away from non-essential, inactive organs such as skin and gut to essential active organs such as the heart and skeletal muscles
• The activity of the gut decreases
• The pupils dilate so that more light can enter the eye.
• Blood coagulability increases to enable speedy coagulation should injury occur
• Inflammation is repressed so decreases resistance to infection
• The central nervous system is aroused so that the person can "learn" or adapt quickly

In the above state the body is ready to physically deal with any threat. If a fight took place or the individual ran at speed for some distance, the above responses would be used to the maximum benefit of the body and recovery to homeostasis would be rapid and smooth.

The Hypothalamus responds to the amount of adrenaline and glucocorticoids in the blood stream. And by negative feedback on the pituitary controls the levels. So as the threat diminishes so do the levels of hormones. However if the stressor is continuous then the levels are kept high and the parasympathetic system cannot do its job.

Normally we would face a stressful situation and the sympathetic nervous system would kick in and put us into a state of arousal. This would help us to deal better with whatever it is that's causing us stress. Then the parasympathetic system fires up and calms us down. Returning our system to a state of balance and relaxation. When it does function like this the stress response is a healthy.

But what happens with stress is that the sympathetic nervous system is continually triggered. Then our parasympathetic system doesn't have the time or opportunity to bring things back to a balance. When the sympathetic nervous system is always switched on it stops being a helpful response. It becomes a nuisance. When we are in "fight or flight" mode we are more likely to respond aggressively at inappropriate times. And this causes yet more stress. So what happens is that our stresses become self-reinforcing. This is when stress becomes a trap.

So what protects us can also damage us. This is called "allostatic load." It's the price the body has to pay for either doing its job less efficiently or simply being overwhelmed by too many challenges. For our metabolism the overactivity of the ANS and increased cortisol secretion produce hyperglycemia (increased sugar levels) As little as a week of inadequate sleep can raise evening levels of blood sugar. If prolonged what can result is a rise of insulin. If this situation goes on for a long time continued hyperactivity of the ANS and elevated cortisol could lead to diabetes as well as a range of other diseases.

When we have completely surpressed the immune system by being in a continual state of arousal we are more likely to suffer from the following stress related diseases:

• Depression
• Coronary heart disease
• Peptic ulcer
• Asthma
• Diabetes
• Lower back pain
• Headaches
• High Blood Pressure
• Arthritis
• Spastic bowel
• Ulcerative colitis
• Gout
• Cancer
• Skin rashes
• Accidents
• Multiple sclerosis
• Mental health problems
• Family violence

While acute stress actually improves our brain's attention chronic stress impairs nerve cells. For the immune system, which is controlled by the nervous system and by circulating hormones, chronic stress suppresses the ability of the immune system to do its job.
But what happens when the body cannot mount an adequate response to an acute stress? They are unable to function normally and replenish energy reserves, enhance memory or move immune cells.