sympathetic nervous system

American  

noun

1. Anatomy. the part of the autonomic nervous system consisting of nerves that arise from the thoracic and lumbar regions of the spinal cord, functioning in opposition to the parasympathetic nervous system, and producing effects such as increasing the heart rate and dilating the pupils.

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sympathetic nervous system Scientific  

/ sĭm′pə-thĕt′ĭk /

1. 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.

2. Compare parasympathetic nervous system

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Example Sentences

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

Depression and emotion may so effect the sympathetic nervous system as to cause a lowered circulatory activity.

From Applied Psychology for Nurses by Porter, Mary F.