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How do the sympathetic and parasympathetic nervous systems differ?

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Diagram of a human figure showing the full nervous system, including the brain, spinal cord, and branching peripheral nerves throughout the body, with labels for each part. — human nervous system The conduction of electrochemical stimuli from sensory receptors in the human nervous system occurs via organized groups of specialized cells, consisting largely of neurons, various neural support cells, and tracts of nerve fibers.

The sympathetic and parasympathetic nervous systems are the two primary, antagonistic divisions of the autonomic nervous system, which regulates involuntary visceral processes to maintain homeostasis.61

Functional Differences

Sympathetic Nervous System: Often associated with the fight-or-flight response, this system prepares the body for stress or imminent danger by increasing heart rate, dilating pupils and bronchi, and redirecting blood flow to skeletal muscles.23
Parasympathetic Nervous System: Associated with rest and energy conservation, this system modulates visceral organs to increase digestive secretions and reduce heart rate. Unlike the sympathetic system, its responses are not activated en masse and it is not considered crucial for the maintenance of life.415

Anatomical Differences

Origin: Sympathetic preganglionic neurons originate in the thoracic and lumbar segments of the spinal cord (thoracolumbar outflow). Parasympathetic neurons originate in the brainstem or sacral segments of the spinal cord (craniosacral outflow).234
Ganglia Location: Sympathetic ganglia are located at a distance from their target organs, whereas parasympathetic ganglia are typically found near or within the tissues they innervate.64