The Fight Or Flight Response – Five Facts You Need to Know

by Farzana Rahman

This is the first in a series of blog posts about the ‘stress response’ and its opposite, the ‘relaxation response’. In this post we talk about the fight or flight response and how stimulation of this pathway leads to physical changes in our body.


The Fight or Flight Response

The fight or flight response is the term used to describe the body’s natural response to an acutely stressful event. 

The term harks back to the choices we imagine our ancient ancestors had to make when faced with life-threatening danger. Did they have time to grab their club and fight the threatening bear who had stumbled into their cave or did they make like lightning and bolt ?

The term ‘fight-or-flight’ was first coined by the American physiologist Walter Cannon.  It described the internal processes that occurred in the body when faced with a threat.

Modern medicine now attributes the fight or flight response as the cause  of chronic stress . Here are five interesting facts about it:


1. The Sympathetic Nervous System

The fight or flight response is modulated by the sympathetic nervous system.  The term nervous system refers to a series of interconnected neurons. When the body faces something it perceives as acute stress, it is this nervous system that is activated.


2. Raging Hormones

Once the sympathetic nervous system is activated, it stimulates the adrenal glands. The adrenal glands are small hormone producing organs that lie at the top of both kidneys. The adrenal glands release hormones called adrenaline and noradrenaline when stimulated by the sympathetic nervous system.  These hormones are known as catecholamines.


3. Adrenaline Rush

Catecholamines have very specific effects on the body. These include:

·      Raised heart rate

·      Increased breathing rate

·      Altered blood flow: blood flows preferentially to the muscles, brains, legs  and  arms.

·      Dilated pupils

·      Trembling and shaking as muscles become tense

These effects all make a lot of sense. The body is priming itself for an attack and giving itself the best chance of fighting. The raised heart rate and breathing rate help metabolism and oxygenation in preparation for energy expenditure. The dilated pupils help us become more aware of our surroundings.


4. Peak Performance

This heightened state of stress can improve performance in any stressful situation.  We may not fight bears anymore, but that rush of adrenaline can help us during a stressful exam or in that presentation we’ve been dreading.


5. Stressed Out

Whilst the fight or flight response is undoubtedly useful, chronic stress is attributed to overstimulation of this pathway.

These days, we often experience stress not from an actual physical stressor, but from stressful thoughts.  Our ability to learn responses is incredible. Once our body associates a thought with a particular physical response, this pathway becomes more and more streamlined and efficient. It’s this streamlined pathway which can lead someone who once had an unexpected stressful experience with spiders to develop a phobia that can be stimulated by just thinking about them.


We’re going to talk about the body’s stress response and its mechanism to counteract this through the ‘relaxation response’ in subsequent posts. Stay tuned !