Difference between Sympathetic and Parasympathetic Nervous Systems


difference between parasympathetic and sympathetic nervous system

Sympathetic vs Parasympathetic Nervous Systems
(Similarities and Differences between Sympathetic and Parasympathetic Nervous Systems)

The involuntary or reflex functions in the body are controlled by a part of peripheral nervous system called Autonomous Nervous System (ANS). ANS regulate the functions of internal organs (visceral functions) particularly the functions of heart, stomach and intestine.  The Autonomic Nervous System composed of two components:

            (1). Sympathetic Nervous System (SNS)

           (2). Parasympathetic Nervous System (PNS or PSNS)

Sympathetic Nervous System (SNS): They are the part of ANS which originate from the spinal cord of the thoracic and lumbar region. They control the ‘fight-or-flight’ response or the ‘sympatho-adrenal response’ in the body. SNS prime the body for acting in threatening situations for survival. The sympathetic nervous system acts in the body as complementary to the action of Parasympathetic Nervous System.

Parasympathetic Nervous System (PNS or PSNS): Part of ANS originates from the spinal cord and medulla which control the ‘rest-and-digest’ or ‘feed-and-breed’ activities in the body. They act in the body as complementary to the action of SNS.

The present post describes the similarities and differences between Sympathetic Nervous System and Parasympathetic Nervous System

Similarities between Sympathetic and Parasympathetic Nervous System

Ø  Both are the part of ANS.

Ø  Both originate from the spinal cord.

Ø  Both have huge influence on physiological process of the body such as respiration, circulation, digestion, urination and reproduction.

Ø  Both have role in maintaining the homoeostasis of the body.

Ø  Both composed of pre-ganglionic and post-ganglionic neurons.

Difference between Sympathetic and Parasympathetic Nervous System

 Sympathetic Nervous System (SNS)Parasympathetic Nervous System (PNS)
OriginOriginated from the cranial, thoracic and lumbar region of the central nervous systemOriginated from the cranial and sacral region of the central nervous system
Main activity in the bodyPrepare the body for intense physical activityRelax the body and inhibit high energy functions
Position of ganglionClose to the spinal cord, away from the effectorAway from spinal cord, close to effector
Size of pre-ganglionic fibresShortLong
Size of post-ganglionic fibresLongShort
Number of post ganglionic fibresLarge numbersVery few numbers
Coverage area of pre-ganglionic fibresCovers a wide areCovers only a restricted area
Mode of effectShow diffused effects in the area of influenceShows localized effects in the area of influence
Transmitter substanceNoradrenaline released at the effectorAcetylcholine released at the effector
Time of dormancyDormant during dangerDormant during rest
Control Control reactions to stressControl routine body activates
Homoeostatic effectExcitatory homoeostatic effectInhibitory homeostatic effect
Effect on blood levelIncreaseDecrease
Effect on metabolic rateIncreaseDecrease
Effect on heart beatIncreaseDecease
Effect on sensory awarenessRaise sensory awarenessRestore sensory awareness to normal level
Effect of pupilDilate pupilsConstrict pupils
Effect on saliva secretionInhibit saliva secretinStimulate saliva secretion
Effect on pulmonary systemDilates bronchial tubulesConstrict bronchial tubes
Adrenaline releaseRelease adrenaline from adrenal glandNor action of adrenal gland
Effect on the conversion of glycogen to glucoseIncrease the rate of glycogen to glucose for muscle powerNor action in the conversion
Effect on urinary outputDecrease urinary outputIncrease urinary output
Effect on rectumRectum is contractedRectum is relaxed


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