Understand Your Nervous System: The "Fight or Flight" vs "Rest and Digest" Modes for Better Health - a podcast by Discussions with successful health experts such as Ben Greenfield, Terry Wa

In the face of stress and anxiety, it is imperative to understand the “fight or flight” versus “rest and digest” sides of the nervous system for optimal health. Our nervous system has two modes of operation, namely, the sympathetic nervous system (SNS), also known as the “fight or flight” mechanism, and the parasympathetic nervous system (PSNS), also referred to as the “rest and digest.” These modes play opposite roles depending on the state we are in.

The sympathetic nervous system (SNS)

The sympathetic nervous system is responsible for voluntary functions, such as controlling the heart rate, digestion, urination, blood pressure, and sweating. It is part of the autonomic nervous system. The SNS is the “fight or flight” mechanism that helps vertebrates to respond to stressful or dangerous situations.

What is the Purpose of SNS?

When facing danger or a stressful situation, SNS is activated to ensure control over the “fight or flight" response. This mode is responsible for the following body changes when facing danger or stress.

• Enlargement of the pupils to enhance vision by allowing more light into the eyes.
• Increasing the heart rate to ensure adequate oxygen supply to other body parts.
• Relaxation of the airway muscles in the lungs for optimal oxygen delivery.
• Reducing the pace of digestion to concentrate the digestive tract’s energy on other body parts.
• Activating the liver energy reserves for quick energy supply.

These changes help in circumstances where fast action or thought is required. The SNS helps in improving eyesight, strength, endurance, and reflexes. The system communicates through neurotransmitters such as epinephrine, norepinephrine, and acetylcholine.

The Parasympathetic Nervous System

The PSNS, or the “rest and digest”, helps relax the body after danger or a stressful situation. It is part of the autonomic nervous system responsible for controlling relaxation. PSNS regulates functions such as metabolism, resting heart rate, and breathing rate.

The Role of PSNS in Response to Stress

During relaxation, the PSNS is responsible for the following body changes.

• Constricting pupils to limit the amount of entering the eyes, enhance close-up vision, and trigger tear production.
• Triggering saliva and mucus production to aid breathing and digestion when the body is in rest mode.
• Reducing the workload for the lungs by constricting airway muscles during rest.
• Reducing heart rate.
• Enhancing digestion rate, diverting energy from other body parts to the digestive tract, and commanding the pancreas to increase the production and supply of insulin.
• Relaxing relevant muscles to facilitate waste removal.
• Controlling sexual functions and arousal feelings.

The "Fight or Flight" Versus the "Rest and Digest" Side of the Nervous System

The contrasts between these two sides of the nervous system include the following.

• While the SNN, or the “fight or flight” mode, increases alertness, the PSNS, or the “relax and digest" mechanism, relaxes the body.
• The PSNS regulates the body’s activities when calm and feeling safe, while the SNS triggers the body to react when its calmness or safety is threatened.
• The SNS contains signals that enhance alertness while the PSNS signals return the body to its standard activity level.
• The SNS acts first to fight or flee, while the PSNS comes later to help the body cool down, relax, rest, and digest.

The two modes of the autonomic nervous system play opposite but complementary roles to maintain body balance.

You may consult Dr. Jason Jones at our Chiropractic office at Elizabeth city, NC to learn more on the battle between the "fight or flight" and the "rest and digest" side of the nervous system.

 

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