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"Fight or Flight" vs. "Rest and Digest"

Most people have heard of the "fight or flight" response of the nervous system, the way in which the body reacts to stress or danger. Many, however, have never heard of the "rest and digest" response. This system activates the more tranquil functions of the body; those that help to maintain a healty, long term balance.

These systems are both part of a larger system named the autonomic nervous system, which controls and influences the way that our internal organs function.

The sympathetic nervous system, or the "fight or flight" responce, prepares our body for action. All of the organs involved in getting ready for a physical challenge (fight) or preparing for a retreat (flight) are activated through this system. The parasympathetic nervous system ("rest and digest") helps produce a state of equilibrium in the body.


The Sympathetic Nervous System

The sympathetic nervous system (SNS) is faster-acting than the parasympathetic system (PNS), and moves along very short, fast neurons. SNS activates a part of the adrenal gland, which than releases hormones into the blodstream. These hormones activate the target muscles and glands, causing the body to speed up and become tense, as well as more alert. Functions that are not immediately essential (like the immune system) are shut down to some degree.

  • heart rate increases
  • pupils dilate
  • muscles contract
  • saliva production is reduced
  • stomach stops many of the functions of digestion
  • the bronchial tubes in lungs dilate
  • more glycogen i9s converted to glucose
  • heart rate increases
  • blood pressure increased
  • releasing a complex mix of hormones and Chemicals such as adrenaline, cortisol and norepinephrine

The Parasympathetic Nervous System

The parasympathetic nervous system (PNS) is much lower system that moves along longer pathways. The parasympathetic response is responsible for controlling homeostasis, or the Balance and maintenance of the body`s systems. It restores the body to a state of calm and counterbalance, and allows it to relax and repair. All of the changes are designed to maintain long-term healt, improve digestion, conserve energy, and maintain the healty Balance in body`s system.

  • digestive enzymes are released
  • saliva is increased
  • heart rate drops
  • blood pressure drops
  • muscles relax
  • bronchial tubes in lungs constrict
  • pupils constrict
  • urinary output increases


The sympathetic nervous system kicks in automatically, and occurs in response to any perceived threat. This doesn`t have to be an imminent physical threat, any perceived threat or stressful situation can trigger this responce. For example, if you have ever felt your heart racing and your mouth dry up ahead of a public speaking engagement, then you know what a sympathetic nervous response feels like. SNS evolved to protect us from real physical dangers like dangerous animals or person. However, it  can also be triggered by the ordinary stressors we face on a daily basis. these might be Things like work deadlines, phones ringing and simply being pulled in too many directions.

Stress is not necessarily a bad thing. The challange is when your body goes into a state of stress in a inappropriate situations.  This can lead to an inability to "think straight"; a state that is a great hindrance in both our work and home lives. If we are kept  in a state of stress for long periods, it can be detrimental to our healt. The results of having elevated cortisol levels can be increase in sugar and blood pressure levels, and a decrease in libido.