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

In the face of a threat, the amygdala sends out a distress signal that activates the sympathetic nervous system and sends adrenaline surging through your body. —Shani Harmon, Forbes, 23 Jan. 2025

One protein, dubbed ADM, particularly stood out with high levels known to play a role in both the sympathetic nervous system (SNS) and hypothalamic–pituitary–adrenal (HPA) activity. —Rich Haridy, New Atlas, 22 Jan. 2025

When under stress, the body activates the sympathetic nervous system, releasing hormones such as adrenaline and cortisol. —Marie Bladt, Vogue, 22 Jan. 2025

At the same time, the sympathetic nervous system dials back functions that are less urgent, like digestion, and moving food through the gut. —Jon Hamilton, NPR, 12 Dec. 2024

Word History

First Known Use

1850, in the meaning defined above

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