What is the Autonomic Nervous System?

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  • Written By: A Kaminsky
  • Edited By: Niki Foster
  • Last Modified Date: 22 September 2019
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Most people are seldom aware of it, but the body’s autonomic nervous system (ANS) regulates much of what they do every day, and it does this largely outside their conscious control. It is part of the peripheral nervous system and regulates many of our most basic functions, such as heartbeat and respiration. This system can be divided into three parts: the sympathetic, parasympathetic and enteric nervous systems.

The sympathetic portion of the system helps the body use energy and is connected to the “fight or flight” response. If a person sees an animal that he is afraid of, he could run the other way or cautiously edge around it. That increased heartbeat, dry mouth and adrenaline surge are all the result of the sympathetic portion of the autonomic nervous system at work.

The parasympathetic nervous system, on the other hand, is all about relaxation. It starts the digestive process, slows the heartbeat and helps the body conserve energy. This is why most fitness experts suggest waiting at least one hour after eating to do any vigorous physical exercise. The body needs energy to digest a meal, as well as for strenuous exercise. A nice walk immediately after dinner might be in order, but a person should hold off on the aerobic jazzercise for an hour or two.


Even such humble, if necessary, functions as salivation, perspiration and the pupils dilating in response to light are jobs for the autonomic nervous system. The ANS also regulates how much the blood vessels dilate, controlling blood pressure.

The enteric system is that mass of nerves and nerve fibers in the gastrointestinal system, and they help regulate digestion and excretion. This system is the reason that a person knows that his bladder is full. Those nerves signal that “full” feeling, telling the person that he needs to use the restroom.

The “full” feeling that comes after a good meal is also the enteric system doing its job. It also tells the stomach how to process foods into amino acids. The loss of control over body functions when scared is an old way of helping the body prepare for flight. A person can run faster on an empty stomach.

Study of the autonomic nervous system is reaping great rewards in the medical field. Scientists are learning ways to fight disease and help improve quality of life through research into this complex system.


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Post 6

Why does it take such a long time to calm down after being scared?

Post 4

Does anyone know why the autonomic nervous system is relevant to the study of emotions?

Post 3

anon22554, i have a feeling it has nothing to do with Mark's autonomic nervous system. there are actually some articles on this site that may be of assistance:

good luck!!! you may also tell him that studies show that men who help with household chores fare better in the bedroom!

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