The Physiology of Chronic Stress

February 10, 2019

Written by: Amanda Leaveck

Not all stress is bad.  Certain stress (ie. interviewing for a job, going on a first date, riding a roller coaster, etc), if experienced in short term bursts, can actually help us grow.   For example, we build muscle mass by applying stress to our muscle tissue.  We learn new information by challenging ourselves to learn. All sorts of hardships, if within our coping abilities, can push us to evolve emotionally.

Furthermore, our biological stress response keeps us alive.  Human bodies have evolved throughout thousands of years to relate to life-threatening stressors in a way that is both intelligent and effective. 

What does the stress response look like?  When we encounter something that may be a threat to our survival, our body responds with a cascade of biological mechanisms that give us the energy, clarity, and focus needed to respond effectively to that stressor.  

A very brief overview of the way our nervous system is organized: our autonomic nervous system is responsible for bodily functions that are not consciously directed (breathing, the heartbeat, digestion, etc).  Two branches of the autonomic nervous system are the sympathetic nervous system (‘‘fight or flight’) and parasympathetic nervous system (‘rest & digest’).  The sympathetic nervous system is designed to mobilize energy and the parasympathetic nervous system is responsible for conserving energy.  If both of these branches are working optimally, the body is in balance (aka, homeostasis). 

When a stressor presents itself, the sympathetic nervous system is activated, which results in the following physiological responses:  

Physiological Effects of the Stress Response

  • Natural fats and sugars that are stored in our system are mobilized for extra energy.  
  • Epinephrine (aka adrenaline) causes our heart to beat faster so that extra oxygen/nutrients are sent to our skeletal muscles quickly, which results in extra power and agility. 
  • Extra oxygen is sent to the brain for immediate clarity.  
  • Endorphins are released and bind to opiate receptors in the brain to lessen our perception of pain (think ‘runners high’). 
  • Dopamine is released to increase psychomotor speed for quick mental processing
  • Increased cortisol levels (the ‘stress’ hormone) keeps the body on high alert, maintaining many of the processes above

In the blink of an eye, we basically become superhuman.  We’ve all been there, too.  Think of a moment in your life where you’ve responded quickly with instinctual power – perhaps you’ve saved yourself or someone from a life threatening accident, or maybe you’ve had to jump out of the way of a moving vehicle.  Your body inherently knows what it needs to do to survive in these moments.  These processes occur beyond our conscious reasoning.  In fact, these physiological responses start occurring even before our vision can process the threat at hand.

The experience of short term, acute stress isn’t bad.  In fact, one could even make the argument that it’s completely natural.  The health risks happen when, over time, the sympathetic nervous system puts the body in overdrive, knocking the entire system out of balance.   The constant presence of stress hormones (cortisol, adrenaline, norepinepherine) become unhealthy over long periods of time for a number of reasons:   

Negative Effects of Chronic Stress:

  • Decrease in digestive activity as blood flow decreases to stomach, kidney, and liver
  • Natural dopamine stores become depleted, which can be linked to the experience of depression, anxiety, and addiction
  • Persistent adrenaline can damage blood vessels and arteries, increase blood pressure, and raise the risk of heart attacks
  • Cortisol keeps the body on high alert, using a lot of energy.  Over time, the body will become exhausted.  The immune system is weakened.
  • The constant presence of high beta brain waves are associated with anxiety, paranoia, chronic pain, and insomnia
  • The hippocampus (the part of the brain associated with long term memory), decreases in size, as stress hormones block the ability of new neurons to be created.

When the parasympathetic nervous system and sympathetic nervous system are out of balance, the body is no longer in homeostasis.  As mentioned previously, homeostasis refers to balance, which is the ability of an organism to regulate its internal conditions and maintain optimal health and functioning (regardless of outside conditions).  As a society, we are on overdrive – not just with our schedules, workload, and commitments, but also within our emotions and thoughts. 

This is why carving out time for ourselves to rest, rejuvenate, and recover is so important.  Without the proper time for stillness, the parasympathetic nervous system doesn’t have the space to rebuild and repair our bodies.  Yoga, meditation, and exercise have all been scientifically proved to reduce the effects of chronic stress on the physical body.

If you want to learn more about the biology behind these process and discover ways to interact with stress in a way that’s healthy, check out my Stress Resilience Virtual Course, a one month experience that offers a deep dive into the human nervous system and stress response.     


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