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How To Gain Maximum Benefit From This Course | Session 1: - Stress | Session 2: - Relaxation | Session 3: - Stress and Exercise | Session 4: - Stress and Nutrition | Session 5: - Stress Resistant Thinking
Stress Management for Health Course
The Fight/Flight Response

".....the 60 pounds of gear I was wearing suddenly weighed nothing....."

(New York Fire Fighter talking about his experience when a building near the World Trade Tower started to collapse and he had to start running for his life)


Fight/Flight - Introduction

Humanity has survived and thrived on this earth for hundreds of thousands of years and through some of the most difficult and stressful times.  One of the factors that has enabled us to survive is a system called the fight/flight response. 

Whenever we perceive we are physically or psychologically threatened we all have an inbuilt, reflex alarm-system in our brain that triggers the release of electrical impulses and a variety of hormones. There is a complex hormonal cascade of over 30 stress hormones, such as adrenaline, noradrenaline and cortisol, which have a powerful and widespread effect on our body's biochemistry, physiology and psychology, giving us the extra strength and speed we need to help us deal with a threatening situation.  If a wild animal attacks us, we can either run away (flight) or if trapped, stand our ground and fight.  This 40,000-year-old model is designed to be used in the short term to deal with physical threats; the stressful situation resolves in a few minutes, either you kill the wild animal or it kills you! 


Modern Life 

The alarm reaction of fight/flight is designed to deal with short-term physical threats in which the emergency is over very quickly in seconds or minutes; but life in the 21st Century is infinitely far more complex than it was 40,000 years ago (or even 50 years ago for that matter). Most of the stressors today are mainly psychological in origin; they are chronic, lasting days, weeks, months, even years in some cases.  Modern stressful events such as financial problems, health worries, work problems, difficult neighbours, relationship problems, etc. can not be resolved by fighting or running away; never the less these psychological stressors still trigger the fight/flight response.

The fight/flight response is designed to be triggered occasionally, however modern living keeps tripping it, making it overactive which can be a factor in causing stress related health problems.  These problems are then made worse by the typical western diet, full of fat and sugar which can cause increased blood clotting, increased blood pressure and can stimulate higher levels of stress hormones in the blood stream. This is then complicated by the fact that we do not get enough physical exercise.  Exercise can help to counter the stress response by - reducing blood clotting, boosting immune function, reducing blood pressure, relaxing muscles, increasing metabolism which burns up stress hormones and making the sympathetic nervous system (which triggers the stress response) less sensitive. 

When the fight/flight response is triggered 1400 different physiological and biochemical changes occur in the body.  But there are also psychological effects making us more alert, aggressive, angry, fearful etc., which all motivate us when we are physically threatened, but have to be suppressed during a meeting with the Bank Manager that doesnt go so well! 

Having said this, the fight/flight response is still an important part of our body's vital defence systems.  Even though the majority of physical threats have gone, there are still situations today where the fight/flight response can be life saving; such as escaping a house fire or speeding up the reflexes to avoid an accident on the motorway. 

For example, a few years ago a farm worker had his arm torn off by a baling machine, yet he was able to pick up his severed arm, carrying it for two miles, to get help.  It was the fight/flight response that enabled him to do this.


Fight/Flight Response and The Autonomic Nervous System

The part of our nervous system that controls the automatic functions of the body (those not under our conscious control such as regulating heart beat, digestion etc.) is called the Autonomic Nervous System (ANS).  

The Autonomic Nervous System is made up of two branches:

1.   The Sympathetic Nervous System (SNS).  This is the system which triggers the biochemical and physiological changes brought about by fight/flight.  Think of it as being a bit like the accelerator on a car or a supercharger on an engine which pumps in more air and fuel to increase speed.

2.   Parasympathetic Nervous System (PNS).  The second part of the ANS is the Parasympathetic Nervous System, which helps to switch off the fight/flight response and return all hormones, organs and systems, back to pre-stress levels.

All of our bodys organs and systems, such as the brain, heart, the endocrine, immune and digestive systems, are hard wired into the autonomic nervous system.  As a result the sympathetic branch can speed up an organ or system and the parasympathetic branch can slow down an organ or system. 


The Two Stages of the Fight/Flight Response

There are 2 co-ordinated stages to the fight/flight response:

1.    Short Term Fight/Flight Response

2.    Long term Fight/Flight Response

1.      Short Term Fight/Flight Response (SAM Axis Sympathetic Adreno Medullary

The SAM or Short term response is the primary system that is triggered in us in response to short term threats.  This is a reflex response, which is electrically triggered.  Electrical impulses from the hypothalamus gland, which is located in the brain, travel along nerves that directly connect to the adrenal glands (these sit on top of the kidneys), to stimulate the release of stress hormones adrenaline and noradrenaline.  Nerve impulses travel at 150 metres per second so this short-term response occurs very quickly, literally in milliseconds; whereas the long-term (HPAC) fight/flight response lasts longer taking several minutes to kick in.   

The body cant sustain the short-term fight/flight response for long because it would become exhausted.  If the stressor is a more chronic one then this triggers the secondary, longer-term fight/flight response to take over. 

2.      Long Term Fight/Flight Response (HPAC Hypothalamic Pituitary Adreno Cortical)

The longer-term fight/flight response is triggered hormonally.  The hypothalamus secretes a hormone called CRF (Corticotropin Releasing Factor), which stimulates the pituitary gland (also located in the brain) to produce ACTH (Adrenocorticotrophic Hormone), which in turn stimulates the adrenal cortex (outer part of the adrenal glands) to release stress steroid hormones like cortisol.  This longer-term fight/flight response is affected by our perception of events, which decide the type and amount of stress hormones that are secreted.  Research has shown that chronic activation of the longer-term HPAC fight/flight response can be a factor in causing a number of psychological and physiological health problems.


When the Stress is Over

The fight/flight response is triggered by the Sympathetic branch of the Nervous System, but three minutes after we perceives that the threat is over, the brain, via the hypothalamus, stimulates the parasympathetic nervous system which switches off the fight/flight response.  The stress hormones fall back to pre-stress levels, reversing all the biochemical and physiological responses; blood pressure falls, heart rate slows down, digestion is stimulated again.


Threats Real or Imagined

The brain cannot distinguish between a real threat, or worry about a potential threat.  It can only respond in one way to both, by triggering the fight/flight response.  For example research has shown that our levels of stress hormones rise when we are just watching a horror film even though we are not physically experiencing the stressor ourselves.


Biochemical and Physiological Changes caused by the Fight/Flight Response  

It has been estimated that the body undergoes 1,400 different biochemical, physiological and psychological changes when the fight/flight response is triggered.  All these changes are designed to give us extra strength and speed to help us fight or run away.  They are vital in the short-term but in the long-term they can have a potentially negative impact on our physical, psychological and social well-being.

Some of the changes that occur include:

         Digestion slows

Blood is diverted from less vital areas such as digestion, to more vital areas such as muscles; digestion slows and stomach acidity increases.

         Breathing Rate Increases

The muscles need extra oxygen for fight-flight.  To supply this extra oxygen requirement our breathing rate speeds up and the airways in the lungs widen.  Breathing switches from relaxed, slow, diaphragmatic breathing, to fast, shallow, chest breathing.

          Pupils Dilate

In order to help us see more clearly, our pupils widen to let in more light.

         Muscles Tense

In order to give us extra speed and strength the muscles of our body tense.


Our hearing improves.

Click below to be taken to the next section

Session 1: Stress - Signs and Symptoms of Stress


S. Jackson D.A.Ac., M.S.A.Ac., M.I.S.M.A. (2003)

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