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Autonomic Nervous System 101

Have you ever been startled awake in the middle of the night by a noise, followed by fear, pounding heartbeat, butterflies in your stomach, and a desire to get to a safer location? Then it turns out it was just the wind outside, or your cat knocking something over? And once you realized you were safe, you felt your heart rate slow down, and you were eventually able to relax and fall back asleep? Well, that whole scenario is an example of your autonomic nervous system in action!


The autonomic nervous system is a part of the peripheral nervous system (PNS) that regulates involuntary actions in the body. It is divided into two components: the sympathetic nervous system (SN) and the parasympathetic nervous system (PN).

Though they’re part of the PNS, the nerves of both the parasympathetic and sympathetic nervous systems originate from the CNS. The nerves that support the parasympathetic nervous system originate from the cranium and the sacrum, and the nerves for the sympathetic nervous system originate from the thoracic vertebrae (a group of bones in the spine that connect to the ribs). From these origin points, they go on to provide nerve function to the organs, blood vessels, muscles, and so forth.


The sympathetic and parasympathetic nervous systems tend to have opposing functions. In general, the sympathetic nervous system (SN) stimulates the emergency “fight or flight” response, while the parasympathetic nervous system (PN) stimulates the “rest and digest” response.

The “fight or flight” response is how the body protects itself from danger. For example, when being chased, one’s sympathetic nervous system jumps into action. Heart rate, breath capacity and circulation (especially more blood to the arms and legs) increase, as other systems like the digestive and immune system turn off to reserve energy for escape (e.g., running away).

The “rest and digest” response is the body’s default mode of function for everyday life. The parasympathetic nervous system is responsible for sustaining normal body functions, a healthy heart rate and blood pressure, allowing the digestive tract to process food and eliminate waste, and restoring and conserving energy for emergencies. PN is also sometimes called the “feed and breed” nervous system because an animal will usually only mate if it is safe from danger. For this reason, sexual arousal is another function of the parasympathetic nervous system.

Though they primarily have opposed duties, the sympathetic and parasympathetic nervous systems do not work exclusively of one another while “fighting” or “resting.” Instead, they work together to create homeostasis (a stable environment). For example, the sympathetic and parasympathetic nervous systems work together to modulate the heartbeat in a push-pull manner. When the heart receives stimulation from the neurons of the parasympathetic nervous system, the heart slows down; and when the heart receives stimulation from the neurons of the sympathetic nervous system, the heart speeds up. Another example of how the two systems work together is that the parasympathetic nervous system is responsible for sexual arousal, but orgasms are controlled by the sympathetic nervous system.

Why and How to Balance the Autonomic Nervous System

To sustain a balanced body, we should employ and live in the parasympathetic nervous system to a greater degree than the sympathetic nervous system. Remember, when the sympathetic nervous system is triggered, some systems like the digestive and immune system shut down. A balanced body requires our systems to function as designed. Therefore, the sympathetic nervous system must be reserved for vigorous workouts and other temporary situations. Unfortunately, many of us—consciously or unconsciously—continuously trigger our sympathetic nervous system. This puts our bodies in a constant state of emergency, which, over time, can put our overall health in jeopardy.

We are stressed—a lot. Stress of the mind and body comes in various forms: financial stress, food stressors (too much or too little food, or poor quality of food), relationship stress, improper sleep, poor air quality, and more. Stress stimulates the sympathetic nervous system. When the sympathetic nervous system is constantly on, many basic body functions are inhibited. The inhibition of these body functions may lead to various conditions and diseases. Excessive stress has been linked to conditions such as anxiety, depression, multiple sclerosis flareups, fibromyalgia, and gastroesophageal reflux disease (GERD), just to name a few.

In short, by stimulating the parasympathetic nervous system, you can live a healthier and more stress-free life. So how can you do that? The first step is to eliminate stressors: get adequate sleep, eat a balanced diet, exercise regularly, and practice relaxation. There are many methods for inducing relaxation, including simple breathing techniques, meditation, restorative yoga, reiki, massage, and more. Regular practice of relaxation techniques increases the amount of time you spend in your parasympathetic nervous system, and increases your ability to access the parasympathetic nervous system and choose relaxation over stress.

Common Ailments

Ailments that affect the autonomic nervous system can happen alone or as a result of another disorder. Autonomic nervous system issues include blood pressure problems, heart problems, trouble breathing, trouble swallowing, and erectile dysfunction. Some ailments that affect the autonomic nervous system include Parkinson’s disease, alcoholism, and diabetes. An imbalanced autonomic nervous system may influence or exacerbate ailments such as gastrointestinal tract ailments, anxiety, depression, fibromyalgia, multiple sclerosis, headaches, and asthma.

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