sympathetic nervous system
Americannoun
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The part of the autonomic nervous system that tends to act in opposition to the parasympathetic nervous system, as by speeding up the heartbeat and causing contraction of the blood vessels. It regulates the function of the sweat glands and stimulates the secretion of glucose in the liver. The sympathetic nervous system is activated especially under conditions of stress.
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Compare parasympathetic nervous system
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The myCAFs release signals that draw in nerve fibers from the sympathetic nervous system, which controls the body's fight or flight response.
From Science Daily ● Feb. 15, 2026
When the researchers blocked the sympathetic nervous system, however, these benefits disappeared.
From Science Daily ● Dec. 6, 2025
A cold plunge can even result in a brief euphoric feeling as your body switches from the parasympathetic to sympathetic nervous system.
From The Wall Street Journal ● Nov. 7, 2025
It turns the human brain into a reptilian one and activates the sympathetic nervous system, putting us into fight-or-flight mode — the same one we can get stuck in when we’re chronically lonely.
From Salon ● Mar. 16, 2025
What part the sympathetic nervous system plays, we do not know.
From Maintaining Health Formerly Health and Efficiency by R. L. Alsaker
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
