Sympathetic nervous system

The part of the autonomic nervous system originating in the thoracic and lumbar regions of the spinal cord that in general inhibits or opposes the physiological effects of the parasympathetic nervous system, as in tending to reduce digestive secretions or speed up the heart.

The part of the autonomic nervous system (ANS) that responds to dangerous or threatening situations by physiologically preparing a person for “fight or flight”. Epinephrine and norepinephrine are the neurotransmitters chiefly involved with this system. Contrast with parasympathetic nervous system.

Part of the nervous system involved in maintaining arousal alertness and muscle tone.

That part of the nervous system that accelerates the heart rate, constricts blood vessels and raises blood pressure.

Part of the autonomic or “involuntary” nervous system over which we have no control. It consists of nerves that release norepinephrine, which constricts arteries and arterioles and increases the rate and force of heart contractions, thereby elevating blood pressure.

A part of the autonomic nervous system that tends to speed up actions of various organs.

Part of the autonomic nervous system, which leaves the spinal cord from the thoracic and lumbar regions to go to various important organs such as the heart, the lungs and the sweat glands, and which prepares the body for emergencies and vigorous muscular activity.

One of the two divisions of the autonomic nervous system (the other being the parasympathetic nervous system), consisting of fibers that leave the central nervous system, pass through a chain of ganglia near the spinal cord, and are distributed to heart, lungs, intestine, blood vessels, and sweat glands. In general, sympathetic nerves dilate the pupils, constrict peripheral blood vessels, and increase heart rate. The system works in balance with the parasympathetic nervous system.

The division of the autonomic nervous system (which controls unconscious, automatic body functions) that directs the body’s responses to stress or danger (the so-called fight- or-flight response). This activity consumes stored energy in the body. Typical sympathetic activity includes widening the air passages in the lungs, increasing heart rate and opening the pupils wider.

One of the two divisions of the autonomic nervous system, having fibers that leave the central nervous system, via a chain of ganglia close to the spinal cord, in the thoracic and lumbar regions. Its nerves are distributed to the blood vessels, sweat glands, salivary glands, heart, lungs, intestines and other abdominal organs, and the genitals, whose functions it governs by reflex action, in balance with the parasympathetic nervous system.

Part of the autonomic nervous system. It consists of scattered collections of grey matter known as ganglia, united by an irregular network of nerve-fibres; those portions where the ganglia are placed most closely and where the network of fibres is especially dense being known as plexuses. The chief part of the sympathetic system consists of two ganglionated cords that run through the neck, chest, and abdomen, lying close in front of the spine. In conjunction with the other part of the autonomic nervous system the parasympathetic this part controls many of the body’s involuntary activities involving glands, organs and other tissues.

The thoracolumbar division of the autonomic nervous system. Preganglionic fibers originate in the thoracic and lumbar segments of the spinal cord and synapse with postganglionic neurons in the sympathetic ganglia. Most of these ganglia are in two chains lateral to the backbone, and others are within the trunk; postganglionic fibers extend to the organs innervated. Some effects of sympathetic stimulation are increased heart rate, dilation of the bronchioles, dilation of the pupils, vasoconstriction in the skin and viscera, vasodilation in the skeletal muscles, slowing of peristalsis, conversion of glycogen to glucose by the liver, and secretion of epinephrine and norephinephrine by the adrenal medulla. Sympathetic effects are general rather than specific and prepare the body to cope with stressful situations.

Subsystem of the autonomic system that triggers your body’s response to stress; known as the fight-or-flight response.

The branch of the autonomic nervous system associated with enervating and activating the organ systems of the body that are involved in the fight-or-flight response.

The branch of the autonomic nervous system that tends to promote motor and mental excitation and is responsible for the “fight or flight” response, symptoms of which include a faster heartbeat, dilated pupils, and digestive and sexual inhibition.

The branch of the autonomic nervous system known as the “fight or flight” response, which heightens heart rate, blood pressure, respiratory rate, and other functions during active or stressful circumstances.

One of the two branches of the autonomic nervous system, the sympathetic nervous system, together with the parasympathetic nervous system, oversees numerous involuntary functions within the body. The sympathetic nervous system heightens bodily functions (such as accelerating the heart rate and expanding blood vessels in muscles) as a way of preparing the body to manage stress.