Sympathetic and Parasympathetic

Sympathetic and Parasympathetic are subdivisions of the autonomic nervous system in vertebrates, closely integrated to govern involuntary physiological responses. The sympathetic nervous system (SNS) primes the body for action during periods of emotional stress, known as ‘fight or flight’ response, causing an increase in heart rate, dilated pupils and accelerated breathing. Conversely, the parasympathetic nervous system (PNS) promotes ‘rest and digest’ activities that occur when the body is at rest, including stimulating digestion, activating metabolism, slowing heart rate, and contracting pupils.

The SNS originates in the spinal cord’s thoracic and lumbar regions while the PNS springs from cranial nerves III, VII, IX, X and sacral segments S2-S4. Both systems work synergistically to maintain homeostasis within the body. They exhibit antagonistic effects on various organs but can also function independently or cooperatively depending on physiological conditions.

At a molecular level, both systems communicate via neurotransmitters; norepinephrine for SNS and acetylcholine for PNS. These neurotransmitters bind to specific receptors on target organs leading to varied responses.

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Sympathetic and Parasympathetic

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Sympathetic, Parasympathetic

Category:
Physiology

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Medical information

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Parent Category:
Health Sciences

Subcategories:
Autonomic Nervous System, Neurology

Synonyms:
Fight or Flight Response (for Sympathetic), Rest and Digest Response (for Parasympathetic)

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Sympathetic nervous system, Parasympathetic nervous system functions

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Autonomic nervous system, Sympathetic vs. parasympathetic nervous system

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Norepinephrine, Acetylcholine