Your sympathetic nervous system is a network of nerves that helps your body activate its “fight-or-flight” response. This system’s activity increases when you’re stressed, in danger or physically active. Its effects include increasing your heart rate and breathing ability, improving your eyesight and slowing down processes like digestion.
Your sympathetic nervous system is part of your autonomic nervous system. It could be called your “automatic” nervous system, as it is responsible for many functions that you don’t have to think about to control. This can include control of your heart rate, blood pressure, digestion, urination and sweating, among other functions.
Your sympathetic nervous system is best known for its role in responding to dangerous or stressful situations. In these situations, your sympathetic nervous system activates to speed up your heart rate, deliver more blood to areas of your body that need more oxygen or other responses to help your get out of danger.
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Your sympathetic nervous system controls your “fight-or-flight” response. Danger or stress activates your sympathetic nervous system, which can cause several things to happen in your body. In response to danger or stress, your sympathetic nervous system may affect your:
These effects help you in situations where you might need to think or act quickly. They improve your eyesight, reflexes, endurance and strength. Your sympathetic nervous system also activates at times when your body’s under strain, like when you’re exercising or are sick.
Your sympathetic nervous system activity also affects your immune system and your body’s repair processes. These effects can help your body start repairs on an injury quickly if you get hurt.
Your sympathetic nervous system uses chemicals called neurotransmitters to communicate. Specifically, these chemicals are norepinephrine, epinephrine and acetylcholine.
Your sympathetic and parasympathetic nervous systems have opposite roles. While your sympathetic nervous system carries signals that put your body’s systems on alert, your parasympathetic carries signals that relax those systems.
The two systems work together to keep your body in balance. Your sympathetic nervous system takes the lead for as long as is necessary to get you through a period of danger. Then, your parasympathetic nervous system steps in and returns things to normal.
Most of the signals that your sympathetic nervous system sends start in your spinal cord. The signals leave your spinal cord and activate structures called ganglia. Your sympathetic ganglia then send the necessary signals far and wide to different parts of your body. This could include your heart, lungs, arteries, sweat glands and digestive system.
The components of your sympathetic nervous system are similar to those found in other parts of your nervous system. The main type of cell is a neuron, which can generate and receive signals.
There are many conditions and causes of sympathetic nervous system problems. Common examples include:
Several potential symptoms can happen with sympathetic nervous system conditions, including:
Potential tests include:
Sympathetic nervous system condition treatments can take many different forms, and ultimately, there’s no one type of treatment or approach to these conditions. Some of them might be as simple as medication or lifestyle changes. Others can be more complicated.
Some treatments focus on an underlying cause, which may resolve your sympathetic nervous system problem at least partially. If a condition isn’t curable, treatments would likely focus on the symptoms and minimizing the condition’s effects and progress.
Prevention can make a big difference with conditions that affect your sympathetic nervous system. In some cases, there’s a chance to delay conditions that aren’t otherwise preventable. Unfortunately, some conditions aren’t preventable, such as those you inherit or have when you’re born.
The best preventive measures include:
A note from Cleveland Clinic
Your sympathetic nervous system is the part of your nervous system that carries signals related to your “fight-or-flight” response. That makes it a key part of your response to stressful situations. Unfortunately, like the rest of your nervous system, this subdivision of your autonomic nervous system is prone to damage from other conditions and injuries. That means taking care of your nervous system overall, including your sympathetic nervous system, is something that’ll go a long way to helping you live a long, healthy life.
Last reviewed by a Cleveland Clinic medical professional on 06/06/2022.
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