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.

---

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

---

Example Sentences

Researchers found that these effects are linked to changes in both the gut and the sympathetic nervous system.

From Science Daily • Mar. 17, 2026

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

"Patients with HD have a slightly more active sympathetic nervous system, which is what drives the fight or flight response, and theoretically have more norepinephrine," Schultz explains.

From Science Daily • Dec. 2, 2024

But the study from Domingos and results from other groups including Imai’s, which pinpointed specific neurons, indicate the sympathetic nervous system plays a bigger role in basic metabolism than expected.

From Science Magazine • May 22, 2024

The disturbance of the sympathetic nervous system produced by the emotional stress and strain of a great excitement or a great disappointment is reflected in the stimulation or inhibition of glandular action.

From Catastrophe and Social Change Based Upon a Sociological Study of the Halifax Disaster by Prince, Samuel Henry