Home Health & Medicine Anatomy & Physiology
Alternate titles: orthosympathetic nervous system, thoracolumbar nervous system
sympathetic nervous system, division of the nervous system that functions to produce localized adjustments [such as sweating as a response to an increase in temperature] and reflex adjustments of the cardiovascular system. Under conditions of
stress, the entire sympathetic nervous system is activated, producing an immediate widespread response called the fight-or-flight response. This response is characterized by the release of large quantities of epinephrine from the adrenal gland, an increase in heart rate, an increase in cardiac output, skeletal muscle vasodilation, cutaneous and gastrointestinal vasoconstriction, pupillary dilation, bronchial
dilation, and piloerection. The overall effect is to prepare the individual for imminent danger. The actions of the sympathetic nervous system occur in concert with other neural or hormonal responses to stress, including increases in corticotropin and cortisol
secretion. In humans, chronic stress results in long-term stimulation of the fight-or-flight response, which leads to constant production and secretion of catecholamines [e.g., epinephrine] and hormones such as cortisol. Long-term stress-induced secretion of these substances is associated with a variety of
physiological consequences, including hyperglycemia [high blood glucose levels], which can lead to type 2 diabetes mellitus, and hypertension [high blood pressure], which can lead
to cardiovascular disease.
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human nervous system: Sympathetic nervous system
The sympathetic nervous system normally functions to produce localized adjustments [such as sweating as a response to an...
Anatomically, the sympathetic preganglionic neurons, the cell bodies of which are located within the central nervous system, originate in the lateral horns of the 12 thoracic and the first 2 or 3 lumbar segments of the spinal cord. [For this reason the sympathetic system is sometimes referred to as the thoracolumbar outflow.] The axons of these neurons exit the spinal cord in the ventral roots and then synapse on either sympathetic ganglion cells or specialized cells in the adrenal gland called chromaffin cells.
The sympathetic nervous system is one of two antagonistic sets of nerves of the autonomic nervous system; the other set constitutes the parasympathetic nervous system.
The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Kara Rogers.
The body’s nervous system is made up of two major parts, the central nervous system, and the peripheral nervous system. These two parts of the nervous system act jointly to
assure your body is communicating all of its sensory information and needs. The central nervous system and the peripheral nervous system each play different roles in controlling your body’s functions. The central nervous system [CNS] is made up of the brain, cerebellum and the spinal
cord The spinal cord directs signals from the brain to the body and is capable of controlling simple reflexes without transmitting information from the brain. The brain processes most of the body’s sensory information and is responsible for coordinating conscious and unconscious body functions including feeling, thinking, and maintaining homeostasis, which is the body’s ability to
maintain a stable environment. The brain is made up of three regions, the forebrain, the midbrain, and the hindbrain. Nerves make up the peripheral nervous system [PNS], which works to send signals to and from the CNS, the body’s organs, muscles, and senses. The PNS is broken into the somatic nervous system and the autonomic nervous system.Central Nervous System
The Spinal Cord
The Brain
Peripheral
Nervous System
Somatic Nervous System
The somatic nervous system is made up of motor neurons and sensory neurons that help the body perform voluntary activities.
Autonomic Nervous System
The autonomic nervous system is made of neurons that work to connect the CNS with the body’s internal organs. It is divided into two parts, the sympathetic nervous system, and the parasympathetic nervous system.
Sympathetic Nervous System
The sympathetic nervous system stimulates what is known as the fight or flight response in the body. It prepares the body’s energy for stressful or energy-exerting activities.
Parasympathetic Nervous System
The parasympathetic nervous system, on the other hand, works to conserve energy. It signals the body to conserve its energy while it sleeps and relaxes.
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