The fight or flight response was first described in 1929 by Walter Canon.  His theory defines what he calls hyper arousal or acute stress response stating that animals react to stress by a general discharge of the sympathetic nervous system preparing them to be able to meet a threat and either fight or flee from that threat.  This response is recognized as the first stage of the general adaptation syndrome regulating stress responses in vertebrates.


With the evolution of fight or flight, fight is manifested in aggressive and combative behavior while flight is manifested by fleeing from potentially threatening situations.  As our lives have been impacted by the changes of modern society so has the fight or flight responses which are now associated with a much wider range of behaviors.  The fight or flight response of males and females is different in dealing with stressful situations.  Males tend to respond to threatening situations more aggressively, while females are prone to flee, seek assistance and help or try to diffuse the situation.  Females however, will be more aggressive if demonstrating a protective response to their offspring and will also affiliate with others to achieve a shared social response to a threat.

Normally when unthreatened and in a relaxed state neuron activity is minimal in the locus coreruleus a nucleus in the brain stem involved with physiological responses to stress and panic.  Once a perception of danger and a threat is detected or an environmental stressor including overly bright light or increased sound levels occurs it is relayed from the brains sensory cortex.

The sensory cortex is an umbrella term for the primary and secondary cortexes of the bodies differing sensors.  This includes the visual cortex on the occipital lobes, the auditory cortex on the temporal lobes, the somatosensory cortex related to touch positioned in the postcentral gyrus, the olfactory cortex on the entorhinal and pyriform cortexes and the gustatory cortex laterally on the postcentral gyrus.  All these sensory areas of the brain are located behind the lateral and central fissure at the back of the brain.  The central fissure divides the primary motor cortex in the precentral gyrus from the sensory cortex in the postcentral gyrus.

The relay of the perception of danger from the sensory cortex occurs through the hypothalamus to the brainstem.  The hypothalamus is that portion of the brain containing small nuclei, just above the brain stem, it has varying functions.  The most import of which is to link the nervous system to the endocrine system. The hypothalamus is responsible for varying metabolic processes and other activities of the Autonomic Nervous System.  It controls hunger, thirst, and body temperature and fatigue.  It synthesizes and secretes neurohormones which in turn stimulate or inhibit the secretion of Pituitary hormones.

The hypothalamus is responsive to several stimuli however in a combative environment or a threatening situation it will respond to stress.  The route of signaling causes an increase of noradrenergetic activity in the locus coerulus enabling the person to become alert to the environment and attentive.  An increase of catecholamines at neuroreceptor sites will facilitate a reliance on spontaneous and intuitive behavior related to combating a threat or fleeing from it.  It is this behavior which we need to develop to enable us to respond instinctively to attacks.

Once a stimulus is defined as a threat the body reacts by an increased and prolonged discharge of the locus coerulus activating the sympathetic division of the autonomic nervous system associated with specific physiological actions within the system.  This is achieved by directly and indirectly by the release of epinephrine or adrenaline and to a lesser extent norepinephrine from the medulla of the adrenal glands.  This release is triggered by acetylcholine which is released from the preganglionic sympathetic nerves.

But what does this physiology which is occurring within our bodies mean to us when we need to respond instinctively in response to an attack.  With what is happening to us mean that our ability to respond will be inhibited or will we develop that 100 meter death stare like a lions prey on the Serengeti Plain in Africa.

Our bodies will respond in ways that we might not be able to control or initially understand. Our bodies automated systems initiate as our intuitive survival skills become active.  As adrenaline is released our pupils in our eyes will dilate, our heart rate will increase as will the force of contraction, the bronchioles in our lungs will dilate, the digestive system shuts down, there will be an increase of secretion of rennin in our kidneys and we may lose bodily control of our sphincter and bladder as well as possible ejaculation in males. However, through all of this we must be able to understand what is happening to us and be prepared for it.  Knowing reduces the uncertainty and fear.  Knowing how our bodies are reacting and taking that knowledge into consideration is essential when training for the development of instinctive defensive skills.

Our body’s immediate physical reactions in preparation for the muscular action required for instinctive response to an attack include the following:

Fight or Flight Our Bodies Natural Physiological Responses

  • Acceleration of heart and lung action
  • The paling and flushing of our skin coloring or alternation between each
  • Digestion slows and or stops
  • Sphincter control
  • Constriction of the body’s blood vessels
  • Dilation of blood vessels within the body’s muscles
  • Increases of fat and glucose for increased muscular action
  • Reduced tear and saliva production by the lacrimal gland
  • Pupil dilation
  • Relaxation of the bladder
  • Erectile dysfunction and or ejaculation
  • Loss of hearing
  • Tunnel vision
  • Shaking of the body
  • Acceleration of instantaneous reflexes

Recalling the GAS system discussed earlier which incorporates the body’s responses to stress including alarm, resistance and exhaustion the Sympathetic Nervous System (SNS) assists the body’s arousal in response to its initial alarm.  The Parasympathetic Nervous System (PNS) enables the body to regain control through the resistance stage and to recover when in the exhaustion stage of the GAS process.

When in a combative environment our body reacts further enabling us to focus on the threat.  However, as this occurs we are exposed to perceptual distortion.  The level of distortion will vary among individuals however; the majority of possibilities are highlighted as follows:

Types of Perceptual Distortion That may be Experienced in a Combative Environment

  • Auditory exclusion, diminished sound
  • Intensification of sound
  • Tunnel vision
  • Automation (scared witless) and temporary paralysis
  • Heightened visual clarity
  • Slow and or fast motion time
  • Memory loss for elements of the event including actions undertaken
  • Disassociation or distracting thoughts
  • Intrusive distracting thoughts
  • Memory distortions

Being aware of perceptual distortion can assist in managing it in association with other methods of calming and controlling our body’s responses.  This is why focus and mental conditioning are very important during our training processes as is understanding the information and knowledge of what our body is experiencing and how we can improve our combative response capabilities through realistic and stressful training practices.  Control of our breathing is an important element of this process.  There are only two automated processes our body conducts that we can consciously control, blinking and breathing.  Breathing control enables us to slow our heart rate where we can still function at an optimum level without our performance and skills deteriorating as well as maintain psychological control and commitment.

For us to be able to respond and defend ourselves instinctively we need to be able to train our bodies capitalizing on the body’s natural physiological responses.  This includes the chemical responses within our body, the acceleration of instantaneous reflexes and the physical changes that are occurring.

To assist in this we need to maintain sound sleeping habits, maintain reduced levels of alcohol and other adverse chemicals in our system and where possible expose our bodies to eustress through realistic training and fitness that increases our body’s endurance when functioning with an increased heart rate, lung capacity and muscular endurance while enhancing our reflexes, balance, coordination and skill bases.  This in turn will also enhance our performance and ability in a combative environment including visual reaction time, complex motor skills and cognitive reaction time.

In addition we need to train mentally adapting our appraisal process and how we condition ourselves to meet these challenges.