Understanding Stress

The Fight, Flight or Freeze Response

As humans developed from ape into primitive people they sometimes needed quick bursts of energy to fight or flee predators such as saber tooth tigers in order to survive. Sometimes, when unable to outrun their predators they would stop lay down and pretend to be dead. Humans, over time, developed an automatic biochemical response to help them deal with dangers that might threaten their survival. These automatic bodily reactions persist in humans today when we are faced with a threat, and are known as the fight, flight or freeze response.

Your nervous system is divided into 2 parts: the voluntary nervous system and the autonomic nervous system. The voluntary nervous system is composed of nerves that connect to muscles which control movement to our arms and legs by sending information to them from our eyes, ears and other senses.

The autonomic part of the nervous system is composed of all of the nerves which connect to the internal organs and glands. It also controls automatic bodily activities such as digestion and breathing. It is a part of the autonomic nervous system which sets off the fight, flight or freeze response and activates our bodies quickly to prepare it to fight, freeze or flee from any danger we perceive as threatening our existence. It does this almost instantaneously. 

How does our nervous system help us when faced with a threat or danger?  The autonomic nervous system will suspend all non-essential activity in the body and increase the activity in systems needed to either fight, freeze, or flee the danger or threat perceived. When the nervous system triggers the fight, flight or freeze response it releases increased amounts of adrenaline and related chemicals into the bloodstream. This provides extra strength, stamina and ability to respond quickly to the danger or threat perceived.

Some of the automatic changes our nervous system will implement instantaneously when faced with a threat are:

  • Accelerated Heartbeat: this pumps more blood to the muscles for the impending struggle.

  • Deeper and More Rapid Breathing: this ensures a large supply of oxygen

  • Increased Muscle Tension: this prepares the muscles for any upcoming action

  • Cold Sweat: prepares the body for the warm sweat from actual muscular activity

  • Constriction of Peripheral Blood Vessels near the Surface of the Body: this raises blood pressure

  • Shivering and the Raising of Hairs: this conserves body heat and protects the body from the increased threat of cold due to the constriction of the peripheral blood vessels

  • Dilation of the Pupils: permits a better view of the threatening danger “eyes wide with fear”

  • Suspension of Digestive Activity: provides additional blood for the motor muscles

  • Dry Mouth due to Decreased Flow of Saliva: this accompanies the decreased flow of gastric juices in the stomach as digestive activity is suspended

  • Tendency Toward Voiding Bladder and Bowels: this frees the body for strenuous activity

  • Suppression of the Immune System and Pain Response: this prevents swelling and discomfort which could interfere with a quick escape

You can see how the fight, flight or freeze response aided our early human ancestors in surviving physical threats such a tigers, snakes and fast developing lightning storms. However, as humans today, we face fewer and fewer physical dangers requiring strenuous action to survive than our ancestors did. The most probable physical threats we face today may be an oncoming car heading toward us, or an overly aggressive panhandler that engages us. In fact, the most common threats we face today are psychological threats as opposed to physical threats. Threats such as the loss of love, status, prestige or our sense of belonging and significance are our most common concerns. These psychological losses usually do not require an immediate physical response. However, if we perceive them as a threat, the nervous system will automatically trigger the fight, flight or freeze response. This will in turn cause instantaneous physical reactions to our bodies that are unnecessary for that particular perceived threat.

What is Stress?

Stress is pressure or tension exerted on a material object.
In the context of this discussion, the material object is a human.
There are 2 forms of stress humans experience:

Physical Stress

Physical stress is created by physical demands on the body such as those caused by accidents, illness, chemical toxins or a demanding physical work schedule.

Psychological Stress

Psychological stress is anything that triggers the fight, flight or freeze response. It is created by mental or emotional demands we place on ourselves. These mental or emotional demands often come from personal beliefs, family,work or friends.


These mental or emotional demands of psychological stress often come from personal beliefs, family, work demands or friends. Here are a few causes of psychological stress:

  • Pressure: an internal or external demand to complete a task or activity either within
    a limited time, or in a specific manner

  • Frustration: the blocking of needs or wants

  • Conflict: the need to make a choice between 2 or more competing alternatives

An important point about stress is that your body reacts to any thought as though the thought concerns an event occurring in the present. It doesn’t matter whether the thought is relates to something in the past, present or future. A vivid thought about a past negative event, or a negative future event can trigger the fight, flight or freeze response in the present.

 A simple example of stress may be the requirement of having to give a speech to a group of 100 people. If the need to give the speech triggers your fight, flight or freeze response then it is a stress in you. This stress, in the form of a speech, will trigger the fight, flight or freeze response because it is perceived as a threat to you in some way. It may be a threat to your status or prestige.  Your fight, flight or freeze response will automatically kick on to enable you to deal with the threat. Your muscles may tense. Your mouth may become dry. Your heart may start to beat rapidly. All of this may occur in the present just while only thinking about the prospect of giving a speech in the future. These reactions which are a result of your fight, flight or freeze response may result in hindering your ability to give a satisfactory and competent speech. ,

However, if you have given many, many speeches in your life, the requirement of giving a speech in front of 100 people may not trigger the fight, flight or freeze response. You may not perceive this as a threat. Thus, this event is not stress for you. You won’t get those reactions of a dry mouth, muscle tension or rapid heartbeat.

From the above example, we can see how the same event may be stress for one person therefore activating the fight, flight or freeze response and its associated symptoms  while the same event may not be stress for another person. Stress ,in fact, can even be positive. Take the example of an athlete taking the field for a big game. The fight or flight response and its flow of blood to muscles may help with his performance. The musician before a performance may be helped by increased sense of hearing and muscle reaction. On the other hand negative stress can be short term such as waiting to board an airplane or long term such as being unemployed for a long period of time.