What is the parasympathetic nervous system?

Updated: Mar 02, 2020
  • Author: Ryan O Stephenson, DO; Chief Editor: Milton J Klein, DO, MBA  more...
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The parasympathetic fibers typically act in opposition of the sympathetic autonomic nervous system through negative feedback control. This action is a complementary response, causing a balance of sympathetic and parasympathetic responses. Overall, the parasympathetic outflow results in conservation and restoration of energy, reduction in heart rate and blood pressure, facilitation of digestion and absorption of nutrients, and excretion of waste products. This parasympathetic response is primarily mediated through cranial nerve X, the vagus nerve, and the S2, S3, and S4 spinal nerves.

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