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How does the autonomic nervous system work?

William B. Salt II., MD
Gastroenterology
There are two branches of the autonomic nervous system (ANS) -- the sympathetic branch and the parasympathetic branch -- which act in opposition to each other. For example, when the sympathetic branch is activated in response to stressors, the parasympathetic branch is inactive, or suppressed. When the parasympathetic branch is activated, the sympathetic branch is suppressed.

Both branches of the ANS originate from the hypothalamus of the emotional motor system of the central nervous system (CNS). They branch out to interface with virtually every organ, blood vessel and sweat gland in your body. The ANS, for example, is at work when a scary event causes your hair to stand on end. When a fear signal is sent from your mind/brain down the "wires" of your ANS, little muscles at the base of each hair follicle are stimulated to raise your hair! Goosebumps occur by the same mechanism.
Irritable Bowel Syndrome & the MindBodySpirit Connection: 7 Steps for Living a Healthy Life with a Functional Bowel Disorder, Crohn's Disease, or Colitis (Mind-Body-Spirit Connection Series.)

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Irritable Bowel Syndrome & the MindBodySpirit Connection: 7 Steps for Living a Healthy Life with a Functional Bowel Disorder, Crohn's Disease, or Colitis (Mind-Body-Spirit Connection Series.)

Fast Facts on IBS: One in five people suffers from the frustrating symptoms of Irritable Bowel Syndrome (IBS). There is no simple answer--no pill, potion, or quick fix--that will cure IBS. But help...

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.