Sympathetic and Parasympathetic Nervous System

Oct 03, 2023

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The human body is a complex machine that functions through various systems and mechanisms. Among these, the nervous system is one of the most important. It is responsible for controlling and coordinating all the body's activities, including movement, sensation, and even our thoughts and emotions. The nervous system is further divided into two main parts: the central nervous system (CNS) and the peripheral nervous system (PNS).

The Autonomic Nervous System

The PNS is further divided into two parts, the somatic and the autonomic nervous system. The somatic nervous system controls voluntary movements, while the autonomic nervous system controls involuntary movements. The autonomic nervous system is further divided into two parts: the sympathetic and the parasympathetic nervous system.

The Sympathetic Nervous System

The sympathetic nervous system is responsible for the body's "fight or flight" response. When we face a stressful or dangerous situation, the sympathetic nervous system is activated. It increases our heart rate, dilates our pupils, and diverts blood from non-essential organs to our muscles, preparing us for action.

sympathetic nervous system

For example, if you suddenly find yourself in a dark alley late at night and hear footsteps behind you, your sympathetic nervous system will be activated. Your heart rate will increase, your palms will sweat, and your muscles will tense, preparing you to either fight or run away.

The Parasympathetic Nervous System

The parasympathetic nervous system, on the other hand, is responsible for the body's "rest and digest" response. It helps us relax and conserve energy. When we are in a calm and safe environment, the parasympathetic nervous system is activated. It slows down our heart rate, constricts our pupils, and increases blood flow to our digestive system.

parasympathetic nervous system

For example, after a long day at work, when you finally get home and sit down to enjoy a meal, your parasympathetic nervous system will be activated. Your heart rate will slow down, your breathing will become deeper and more regular, and your digestive system will start working efficiently to break down the food.

The Balance Between the Two Systems

Both the sympathetic and parasympathetic nervous systems are essential for our survival. However, they need to be balanced for optimal health. If one system is overactive, it can lead to various health problems. For example, an overactive sympathetic nervous system can cause chronic stress, anxiety, and high blood pressure. Similarly, an overactive parasympathetic nervous system can lead to digestive problems and fatigue.

balance between two systems

Therefore, it is essential to maintain a balance between the two systems. This can be achieved through various techniques, such as deep breathing, meditation, yoga, and exercise. These techniques can help activate the parasympathetic nervous system and promote relaxation and stress reduction.


The sympathetic and parasympathetic nervous systems are two important parts of the autonomic nervous system. They work together to maintain the body's balance and ensure optimal health. By understanding how these systems work, we can take steps to maintain their balance and promote our overall well-being.