sympathetic nervous system

noun

: the part of the autonomic nervous system that contains chiefly adrenergic fibers and tends to depress secretion, decrease the tone and contractility of smooth muscle, and increase heart rate compare parasympathetic nervous system

Examples of sympathetic nervous system in a Sentence

Recent Examples on the Web

Sustained activation of the sympathetic nervous system promotes the production of pro-inflammatory cytokines, leading to a state of constant, low-grade inflammation throughout the body. —Daniel Combs, Verywell Health, 9 Mar. 2026

So, reductions in things like our heart rate and blood pressure as a result of changes in our sympathetic nervous system activity. —Dana Taylor, USA Today, 4 Mar. 2026

Heat activates the sympathetic nervous system. —Christopher McFadden, Interesting Engineering, 21 Feb. 2026

The response resembles what happens during mild exercise, which is a temporary activation of the sympathetic nervous system sometimes described as a fight-or-flight response. —Deirdre Bardolf, FOXNews.com, 14 Feb. 2026

Word History

First Known Use

1850, in the meaning defined above

Rhymes for sympathetic nervous system

• cryptosystem
• ecosystem
• intersystem
• multisystem
• photosystem
• subsystem

Kids Definition

sympathetic nervous system

noun

: the part of the autonomic nervous system that is concerned especially with preparing the body to react to situations of stress or emergency, that controls expansion of the pupil of the eye and air passages, increases the heart rate, slows digestion, and narrows most blood vessels, and that is made up of nerve fibers that trigger the release of norepinephrine compare parasympathetic nervous system

Medical Definition

sympathetic nervous system

noun

: the part of the autonomic nervous system that is concerned especially with preparing the body to react to situations of stress or emergency, that contains chiefly adrenergic fibers and tends to depress secretion, decrease the tone and contractility of smooth muscle, increase heart rate, and that consists essentially of preganglionic fibers arising in the thoracic and upper lumbar parts of the spinal cord and passing through delicate white rami communicantes to ganglia located in a pair of sympathetic chains situated one on each side of the spinal column or to more peripheral ganglia or ganglionated plexuses and postganglionic fibers passing typically through gray rami communicantes to spinal nerves with which they are distributed to various end organs

called also sympathetic system

compare parasympathetic nervous system