Your parasympathetic nervous system is a network of nerves that relaxes your body after periods of stress or danger. It also helps run life-sustaining processes, like digestion, during times when you feel safe and relaxed. The informal descriptions for this system include the rhymes “rest and digest” or “feed and breed.”
Your parasympathetic nervous system is part of your autonomic nervous system. It could be called your “automatic” nervous system, as it’s 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.
The parasympathetic part of your autonomic nervous system balances your sympathetic nervous system. While your sympathetic nervous system controls your body’s “fight or flight” response, your parasympathetic nervous system helps to control your body’s response during times of rest.
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Your parasympathetic nervous system’s job is usually to relax or reduce your body’s activities. Because of the signals it carries, the rhyming phrases “rest and digest” or “feed and breed” are easy ways to remember what your parasympathetic nervous system does.
Your parasympathetic nervous system can have the following effects:
Your sympathetic and parasympathetic nervous systems have opposite but complementary roles. Your sympathetic nervous system carries signals that put your body’s systems on alert, and your parasympathetic carries signals that return those systems to their standard activity levels.
Your sympathetic nervous system takes the lead when your safety and survival are at risk, but that system’s actions can strain body systems when it’s active for too long. Because these two systems offset each other, they help maintain balance in your body.
Your parasympathetic nervous system also manages the activity in organs throughout your body when you feel calm and safe. These functions don’t involve risk or danger but are still key in keeping you alive and healthy.
Your parasympathetic nervous system is one of two parts of your autonomic nervous system. Your autonomic nervous system is a subsystem of your peripheral nervous system, which is all the nervous tissue in your body excluding your brain and spinal cord.
Your parasympathetic nervous system uses four of your 12 cranial nerves. These are nerves that connect directly to your brain. Three of those four only involve your senses and glands connected to your eyes, nose and mouth.
The fourth, your vagus nerve, connects to part of your mouth and also extends down through your neck to your chest and abdomen (belly). Your vagus nerve makes up about 75% of your parasympathetic nervous system overall, connecting to your heart, lungs and other vital internal organs.
Farther down, 31 spinal nerves connect directly to your spinal cord, but your parasympathetic nervous system only uses some of them in the lower part of your spine. This sends signals to your bladder and bowels to relax so you can use the bathroom.
Your parasympathetic nervous system’s components are similar to those found in other parts of your nervous system. Neurons are the main type of cell — they can generate and receive signals.
Many conditions and problems can affect your autonomic nervous system, including your parasympathetic nervous system. Potential problems include:
Your parasympathetic nervous system controls processes in your body that should happen automatically. That means these problems usually get noticed when something doesn’t happen as expected. Possible symptoms include:
Potential tests include:
Treating conditions that affect your parasympathetic nervous system is often challenging. That’s because the treatments can change dramatically, depending on what’s behind the problem. The treatments can also include many different approaches, ranging from medication to surgery.
Sometimes, treatment of a parasympathetic nervous system problem requires treating or curing an underlying problem. In other cases, a condition isn’t curable, and the goal will be to treat and minimize the impact of symptoms.
Prevention can make all the difference in protecting and maintaining your parasympathetic nervous system. The best preventive measures include:
A note from Cleveland Clinic
Your parasympathetic nervous system is a key part of your body’s long-term survival. This system constantly works without you thinking about it, whether you’re asleep or awake. It helps relax you in times of calm and provides a balance with your body’s short-term survival responses. While conditions that affect it are rare, protecting your parasympathetic nervous system is still important to your overall health and well-being.
Last reviewed by a Cleveland Clinic medical professional on 06/06/2022.
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