Sympathetic vs. Parasympathetic: What is the difference between Sympathetic and Parasympathetic?

Sympathetic vs. Parasympathetic: discover their Differences, Similarities, Pros & Cons, as well as their Examples. We also will answer some of your frequently asked questions and find which is more important.
Sympathetic vs. Parasympathetic: Differences, Similarities, and Examples

Sympathetic vs. Parasympathetic: Both Sympathetic and Parasympathetic Nervous Systems are a part of your body’s Autonomic Nervous System but are responsible for different functions. The most significant difference between Sympathetic and Parasympathetic Nervous Systems lies in the body’s response. While the former prepares the body for instant activity, the latter inhibits it from working. 

Defining Sympathetic vs. Parasympathetic Nervous Systems for understanding

What is the Sympathetic Nervous System?

The Sympathetic Nervous System is a part of the Autonomic Nervous System responsible for alerting the body suddenly.

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What is the Parasympathetic Nervous System?

The Parasympathetic Nervous System is a part of the Autonomic Nervous System responsible for calming the body.

Listing the similarities between Parasympathetic and Sympathetic Nervous System

  • Both are part of the Autonomic Nervous System of our body.
  • Both Sympathetic and Parasympathetic nerves are involved in involuntary functions of the body.
  • Both Sympathetic and Parasympathetic Divisions of the Autonomic Nervous System impact the physiological processes of the body. Such processes include digestion, circulation, respiration, reproduction, and urination. 
  • Pathways of both are composed of the preganglionic and postganglionic neurons. 

Considering the pros and cons of both the systems

Pros of Sympathetic Nervous System

  • It prepares your body for emergencies.
  • It alerts your body immediately.

Cons of Sympathetic Nervous System

  • It brings your body out of the resting position.
  • An active Sympathetic Nervous System won’t allow you to sleep.
  • Your blood pressure and heart rate will increase suddenly with an overactive sympathetic system.

Pros of Parasympathetic Nervous System

  • It prepares your body for rest.
  • It helps you enjoy a sound sleep.

Cons of Parasympathetic Nervous System

  • Your alertness levels drop significantly.
  • Your blood pressure and heart rate will decrease suddenly with an overactive parasympathetic system.

Is sympathetic or parasympathetic faster?

When considering the Sympathetic vs. Parasympathetic Nervous System for speed of action, the former is faster. Since the Sympathetic Nervous System has a shorter neuron pathway, it tends to be faster than the Parasympathetic. 

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List down some examples of the parasympathetic and sympathetic systems of the brain

Here are some examples of the sympathetic and parasympathetic systems of the brain:

Examples of the sympathetic systems

  • It increases blood pressure and heart rate.
  • It dilates the pupils and bronchial tubes.
  • It decreases the production of saliva.
  • It releases adrenaline.

Examples of the parasympathetic systems

  • It decreases blood pressure and heart rate. 
  • It constricts the pupils and bronchial tubes.
  • It increases the production of saliva.

How does the activation of the sympathetic nervous system affect your body?

With the activation of the Sympathetic Nervous System, the body goes into hyperactive mode along with getting goosebumps (piloerection). The blood pressure increases, the heartbeat accelerates, blood vessels constrict, bronchial passages widen, pupils dilate, and the perspiration rate increases.

Is blood pressure sympathetic or parasympathetic?

Though both the branches have their roles in impacting blood pressure, the Sympathetic Nervous System plays a significant role in regulating blood pressure. 

How do you activate the parasympathetic system?

Since Parasympathetic System induces a calming state in the body, it can be activated by activities like:

  • Practicing yoga
  • Spending time with nature
  • Splashing cold water on the face
  • Meditation
  • Getting a massage
  • Praying
  • Practicing deep breathing
  • Mild exercising
  • Cultivating healthy intestinal bacteria.

How is the body affected by a damaged parasympathetic nervous system?

A damaged Parasympathetic Nervous System would mean a broken pathway for all the messages being exchanged between the brain and the related organs. The major organs affected would be the ones connected to the Vagus Nerve, like the liver, kidneys, pancreas, stomach, bladder, gallbladder, vagina, penis, and anal sphincter. 

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How do you calm an overactive sympathetic nervous system?

The best way to calm an overactive Sympathetic Nervous System is to release the pent up energy by channeling it the right way. Such ways include major lifestyle changes that include calm-inducing activities like yoga, meditation, creative practices like drawing or painting, etc. It can also be brought back to normal by consciously reducing stress by adopting an optimistic life approach.

What triggers the sympathetic nervous system?

Stress triggers the Sympathetic Nervous System.

Is increased heart rate sympathetic or parasympathetic?

With stress kicking in, the heart rate increases. Thus, the Sympathetic Nervous System is responsible for it. 

Differentiating between the sympathetic and parasympathetic nervous system

Drawing up a sympathetic vs. parasympathetic chart or table will help you understand the difference between them better: 

BasisSympathetic Nervous SystemParasympathetic Nervous System
FunctionIts function is to prepare the body for stress or a potential danger.Its function is to prepare the body to move into a calm state. 
Systemic effectIt involves an ‘alarm’ effect, i.e., fight or flight response.It involves ‘homeostasis’ maintenance, i.e., permitting rest and digest response. 
LocationIt is located near the thoracic and lumbar regions in the spinal cord.It is located between the spinal cord and the medulla. 
Blood pressureBlood pressure increases.Blood pressure decreases.
Blood flowBlood flow decreases to the digestive tract.Blood flow increases to the digestive tract.
Stress hormonesProduction of stress hormones like cortisol increase as a result of perceived danger.Production of stress hormones decreases to induce the feeling of relaxation. 
Blood sugarGlucose is quickly released to match up the enhanced energy levels.Blood sugar levels stay normal as the body enters the resting state. 
Response timeSince the neuron pathways are short, the response time is faster.With longer neuron pathways, the response time is slower. 
Salivary glandsSalivary glands decrease saliva production. Salivary glands produce more saliva.
Adrenal glandIt releases adrenaline.There is no action by the adrenal gland.
PupilsThe pupils dilate.The pupils constrict.
HeartbeatHeartbeat increases.Heartbeat slows down with a calming effect.
GallbladderIt inhibits the gallbladder activity.It stimulates gallbladder activity.
IntestinesIt inhibits intestinal activity.It stimulates intestinal activity.
LungsThe airway relaxes.The airway constricts.

Comparison Chart

Sympathetic vs. Parasympathetic: discover their Differences, Similarities, Pros & Cons, as well as their Examples. We also will answer some of your frequently asked questions and find which is more important.

Comparison Video

Sympathetic vs Parasympathetic Nervous System | Physiology

What is more important between Parasympathetic and Sympathetic Nervous Systems?

Conclusion: Both these systems are important for the efficient functioning of our bodies. The Sympathetic Nervous System alerts our body in emergencies and helps us take appropriate action immediately. On the other hand, the Parasympathetic Nervous System restores our bodies to a state of rest by calming down internal organs’ functioning.


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Alex Stantor
Alex Stantor

Alex Stantor is a Sorbonne University (Paris, France) graduate in Philosophy and Data Analysis. Currently, he is an Author and Researcher at Difference 101, he writes articles/blog posts on topics such as "thinking differently" and "the importance of difference". Alex is a passionate advocate of diversity in the workplace and in companies, and diversity and inclusion in corporate communications. He currently lives in Brooklyn.

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