The Sympathetic vs Parasympathetic Nervous Systems


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The sympathetic and parasympathetic nervous systems 1 2 are two parts of the autonomic nervous system (ANS) which in its turn is part of the central nervous system (CNS). The ANS is responsible for controlling involuntary body functions such as respiration, heart rate, digestion, and more. These two systems work together to maintain homeostasis in our bodies.

It’s important to understand the differences between these two systems in order to effectively manage stress levels and lead an overall healthier lifestyle. If we can learn how to balance these two systems, then we can benefit from improved mental clarity, better sleep patterns, and increased energy levels – all components necessary for achieving a subconscious desire for freedom.

So let’s dive into what makes up these two systems so that you can take charge of your health!

The Divisions Of The Autonomic Nervous System

Key Takeaways:

  • The Sympathetic and Parasympathetic Nervous Systems, components of the Autonomic Nervous System (ANS), regulate involuntary bodily functions and work together to maintain body homeostasis.
  • The Sympathetic Nervous System triggers the body’s fight or flight response during stressful situations, enhancing alertness, and increasing heart rate and blood pressure, among other changes.
  • The Parasympathetic Nervous System, on the other hand, promotes relaxation, digestion, and energy conservation, restoring balance when the body is at rest.
  • Both of these systems use neurotransmitters such as epinephrine, norepinephrine, and acetylcholine to interact with other body systems, aiding in everyday functioning and maintaining health both physically and emotionally.
  • Understanding and managing these systems can lead to better stress management, improved mental clarity, better sleep, and increased energy levels.

The central nervous system consists of two main parts: the autonomic nervous system (ANS) and the peripheral nervous system (PNS) and is the master control of our bodies, governing how we think and feel, move, and rest. The ANS is composed of two parts, the sympathetic nervous system and parasympathetic nervous system, both working together to control involuntary bodily functions.

At its core, the ANS is a communication network between your brain and spinal cord and your body’s organs. This network helps maintain balance in your body by controlling heart rate, blood pressure and digestion. It also responds to stress with a “fight or flight” response that prepares you for physical action.

The sympathetic nervous system controls this fight or flight response as it activates systems throughout your body that gets you ready for action – increasing heart rate, constricting blood vessels and sending more oxygen-rich blood to muscles among other responses. On the other hand, the parasympathetic nervous system has a calming effect on the body – slowing down heart rate, increasing digestive activity and allowing bodily functions to return to normal after intense activity.

Together these two parts of the autonomic nervous system work in tandem to keep us balanced in all kinds of situations; allowing us to remain alert yet relaxed when needed most.

The Role Of The Sympathetic Nervous System

The sympathetic nervous system is a key part of the autonomic nervous system, responsible for triggering the body’s fight or flight response. It helps us respond to stressful and dangerous situations by activating our cardiovascular system and preparing us to either fight or flee the situation. Here are four ways the sympathetic nervous system prepares us for difficult situations:

  • It triggers the release of hormones such as adrenaline, which can make us more alert and prepare our bodies to respond quickly.
  • It increases heart rate and blood pressure, which helps circulate oxygen-rich blood throughout our bodies faster.
  • It causes increased respiration, which allows for deeper breaths that can help prevent fatigue during physical activity.
  • It puts muscles into a state of readiness so that they can act quickly if needed.

In essence, the sympathetic nervous system is our body’s way of preparing us for potentially dangerous or stressful situations so that we can react appropriately and protect ourselves from harm. And while it’s natural to have moments of fear or anxiety when faced with a challenging situation, understanding how your body responds is an important part of managing stress in everyday life.

From here we can explore how the parasympathetic nervous system works in tandem with the sympathetic one to keep our bodies balanced and healthy in times of need.

The Role Of The Parasympathetic Nervous System

The Parasympathetic Nervous System (PNS) is the counterpart to the Sympathetic Nervous System (SNS). Where the SNS is responsible for initiating and responding to stress, the PNS is responsible for calming and restoring balance. It helps us to relax, rest, digest and conserve energy. When it’s active, we feel at ease and contentment.

The parasympathetic nervous system functions via two nerve pathways known as cranial nerves and sacral nerves. The cranial nerves originate in the brain stem and control activities such as salivation, digestion, urination, defecation, respiration, pupillary constriction and heart rate.

The sacral nerves originate from the sacral region of the spine and control sexual arousal, urination and defecation. Both components help to restore balance in our body when we are in a state of rest or relaxation.

When this balance is disrupted by stressors like fear or anxiety our sympathetic nervous system kicks into action while our parasympathetic nervous system slows down its activity so that we can respond appropriately to any threatening situation.

Our body needs a balance between these two systems in order to stay healthy physically and emotionally. By understanding how each of these systems work together we can learn how to better manage our responses during times of stress and find ways of restoring balance in order to live a more relaxed life.

What Do You Feel When The Sympathetic Nervous System Is Active?

As stated earlier, when the sympathetic nervous system is active, your body is preparing for an emergency or a perceived threat. Your body responds with a surge of adrenaline and hormones that heighten your senses and help you react quickly.

Your heart rate speeds up, your blood pressure increases and your sweat glands become more active. All these changes help to ensure that you are ready to respond to any danger or stressors in your environment.

The Sympathetic vs Parasympathetic Nervous Systems
The sympathetic vs parasympathetic nervous systems

At the same time, your digestion slows down and non-essential functions such as reproduction and growth are put on hold until the situation has been resolved. The energy you need to take action is shifted away from these non-essential functions, so you can focus on responding to whatever challenge lies ahead of you.

These rapid physical changes can be quite intense, especially if there is no real emergency taking place. It can lead to feelings of anxiety or fear as your body prepares for something that may not even happen. Knowing how this system works can help you recognize when it’s activated and take steps toward calming yourself down before it gets too overwhelming.

What Do You Feel When The Parasympathetic Nervous System Is Active?

When the Parasympathetic Nervous System is active, we typically experience physical sensations such as deep breathing, slower heart rate and lower blood pressure. We may feel a decrease in stress levels and an overall feeling of relaxation.

This system is regulated by the vagus nerve which runs from your brainstem to your abdomen, connecting many organs along its path.

These physical sensations are key indicators that our body is achieving balance and harmony within itself. When we are relaxed and at ease, we can focus more on positive thoughts and feelings like gratitude, joy, creativity and connection with others – all necessary for our mental well-being. Allowing yourself time to relax will help you access this inner balance so that you can better manage stress in daily life.

It’s important to remember that both the Sympathetic and Parasympathetic systems work together to keep us functioning optimally; they need each other in order to maintain balance and homeostasis in our body.

What Is Homeostasis?

Homeostasis is a process that occurs in the body to maintain stability and balance. It involves regulating and maintaining the balance of hormones, temperature, water levels, and other variables. The sympathetic and parasympathetic nervous systems play an essential role in homeostasis by responding to environmental stimuli and helping conserve energy.

Here are three ways the sympathetic vs parasympathetic nervous system helps maintain homeostasis:

  • Regulation of Autonomic Nervous System Activity: The sympathetic nervous system stimulates arousal and activates fight-or-flight responses while the parasympathetic nervous system calms down the body and initiates restorative functions.
  • Regulation of Body Temperature: The nervous system helps regulate body temperature by releasing heat-producing agents when it gets too cold or cooling agents when it gets too hot. This helps keep the body temperature within its optimal range.
  • Regulation of Metabolism: The sympathetic vs parasympathetic nervous systems also help regulate metabolism by stimulating digestion, releasing insulin, and breaking down food into usable energy for cells to use throughout the body.

By maintaining homeostasis in the body, these two systems help keep us healthy and functioning at our best possible level. With their combined efforts, our bodies are able to respond quickly to changes in our environment while conserving energy to keep us going strong all day long!

Neurotransmitters Of The Autonomic Nervous System

In the sympathetic nervous system, neurotransmitters such as epinephrine and norepinephrine are released when a person is aroused or in danger. This causes an increase in heart rate, respiration, and blood pressure. It also activates the fight-or-flight response that prepares us for physical activity or stress.

In the parasympathetic nervous system, neurotransmitters like acetylcholine are released to help relax the body. This can slow heart rate, decrease respiration, and lower blood pressure. It also promotes restful activities like digestion or sleep.

How The Autonomic Nervous System Works With Other Body Systems

When it comes to how the body works, the autonomic nervous system plays an important role. It is responsible for controlling many of our unconscious processes and functions, such as breathing, digestion, heart rate, and blood pressure. This complex network communicates with other body systems in order to keep us functioning properly. Here’s a look at how:

  • The autonomic nervous system helps regulate hormones from the endocrine system. Hormones are chemical messengers that travel through the bloodstream and carry signals throughout the body. The autonomic nervous system helps to control their release so they can work properly and maintain balance within the body.
  • It works with the cardiovascular system to regulate blood pressure. The autonomic nervous system sends signals to your blood vessels that tell them whether or not to constrict or dilate, helping to regulate blood flow and keep your blood pressure within a healthy range.
  • It assists in managing respiratory functions. The autonomic nervous system helps the lungs take in oxygen by telling the diaphragm when to contract and relax during inhalation and exhalation respectively. It also helps make sure that you’re taking enough breaths even when you’re sleeping or performing strenuous activities without having to think about it consciously.
  • It affects digestion by influencing how quickly food moves through your gastrointestinal tract, as well as how much saliva is produced in order for food to be broken down more efficiently during digestion.

Overall, our bodies rely heavily on our autonomic nervous systems for their day-to-day functioning – it is constantly communicating with other body systems in order for us to remain healthy and balanced emotionally and physically. By understanding this complex network better, we can learn more about ourselves and take steps toward living healthier lives with greater peace of mind!


The sympathetic nervous system and parasympathetic nervous system are the two sides of the autonomic nervous system. They work together to help us maintain homeostasis and keep us healthy. When they become unbalanced, we can experience a variety of symptoms ranging from fatigue to anxiety.

In order to restore balance and ensure that our body remains in peak condition, it is important to make lifestyle changes that will help support both the sympathetic and parasympathetic nervous systems. Regular exercise, stress management techniques, breathing exercises, and relaxation practices can all be helpful in restoring balance.

I encourage my clients to take time out of their busy schedules to focus on self-care activities that will help promote balance between the sympathetic and parasympathetic nervous systems. While these activities may seem like a luxury or an inconvenience at first, they can have lasting positive benefits on both physical and mental health. Taking care of yourself is an investment in your long-term well-being!

See our overview of the stress response, what it is, how your body and brain react to it, and which part the vagus nerve plays.

Frequently Asked Questions

What is the difference between the sympathetic and parasympathetic nervous systems?

The sympathetic and parasympathetic nervous systems are both part of the autonomic nervous system and control many of the body’s involuntary functions. The sympathetic nervous system is responsible for the “fight or flight” response, preparing the body for physical activity in response to a perceived threat. The parasympathetic nervous system, on the other hand, controls the “rest and digest” response, promoting relaxation and digestion. These two systems work together to maintain balance and regulate various bodily functions.

How do you remember the difference between the sympathetic and parasympathetic nervous systems?

One way to remember the difference between the sympathetic and parasympathetic nervous systems is to think of the sympathetic system as being “excitatory” and the parasympathetic system as being “inhibitory.” The sympathetic system prepares the body for action, while the parasympathetic system helps to calm the body down and promote rest and relaxation.

What is an example of a parasympathetic response?

One example of a parasympathetic response is the act of digestion. When we eat, the parasympathetic nervous system is activated, stimulating the production of digestive enzymes and increasing blood flow to the digestive system. This helps to break down food and absorb nutrients from it.

What is a sympathetic and parasympathetic response example?

An example of a sympathetic response would be the “fight or flight” response. In a dangerous or stressful situation, the sympathetic nervous system is activated, increasing heart rate and breathing, dilating pupils, and redirecting blood flow to the muscles. An example of a parasympathetic response would be slowing down the heart rate and breathing and promoting relaxation and digestion after a meal.

What are the similarities between the parasympathetic and sympathetic nervous systems?

The sympathetic and parasympathetic nervous systems have several similarities, including their role in regulating many of the body’s involuntary functions, their control of smooth muscle and glandular tissue, and their communication with the same organs and systems in the body. Both systems also work together to maintain homeostasis and keep the body in balance.


  1. Parasympathetic Nervous System (PSNS): What It Is & Function ([]
  2. Physiology of the Autonomic Nervous System – PMC ([]

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Alex Reijnierse