What does the peripheral nervous system do?
Your peripheral nervous system has two main subsystems: autonomic and somatic.
- Autonomic: These are nervous system processes your brain runs automatically and without you thinking about them.
- Somatic: These are functions you manage by thinking about them.
Those two subsystems are how your peripheral nervous system does its three main jobs:
- Senses: Your PNS is a key part of how your brain gets information about the world around you. This job falls under the somatic nervous system.
- Movement: Your peripheral nerves deliver command signals to all the muscles in your body that you can consciously control. This job also falls under the somatic nervous system.
- Unconscious processes: This is how your brain runs critical processes that don’t depend on your thinking about them. Examples of this include heartbeat and blood pressure. This job depends on your autonomic nervous system.
Senses
Your brain is like a powerful supercomputer. However, it knows nothing about the world outside your body without outside input. That’s why your peripheral nervous system is so important. A computer needs peripheral devices like a camera, microphone or keyboard to give it information from outside itself, and your brain is the same.
Your peripheral nervous system is how your brain gets information about the outside world. Most of your peripheral nervous system travel to the rest of your body by exiting or entering your spinal cord. Your cranial nerves are unlike other peripheral nerves in that these very special nerves connect directly to your brain. These nerves carry signals from your nose, ears and mouth, as well as many other organs. Your cranial nerves also give you a sense of touch in the skin of your face, head and neck.
Other peripheral nerves intertwine throughout every part of your body. They stretch out everywhere, including to the tips of your fingers and toes. The sensory nerves in your hands and feet are also part of your brain’s ability to get information from the outside world. The motor nerves allow you to move various parts of your body.
Movement
Your peripheral nerves that branch outward throughout your body deliver command signals from your brain to your muscles. That allows you to move around and do all kinds of tasks, ranging from simple ones, like scratching your nose, to complicated ones, like juggling.
Unconscious processes
Your autonomic nervous system functions without you thinking about it. Part of your brain is always working, managing processes that keep you alive. Your brain needs your peripheral nervous system to control those functions. Examples of these processes include your heart rate, breathing, blood pressure and your gut’s digestion of food.
Types of nerve signals
Your nerves consist of bundles of nerve cells, which have long, arm-like extensions called axons. The nerve cells and their axons twist and intertwine together to form nerve fibers. This is similar to how multiple strands of spun cloth fibers twist together to form sewing thread. Some of the nerves in that bundle carry information into your brain, while others carry information out of your brain.
- Sensory: These nerves carry information to your brain and spinal cord. They either connect directly to your brain through your cranial nerves or carry information to your spinal nerves, which then feed into your spinal cord. The sensory nerve connections to your spinal cord are on the back of your spinal cord.
- Motor: These nerves carry command signals from your brain to various parts of your body. They only carry information away from your brain. The motor nerve connections are on the front of your spinal cord; meaning, these nerves are for sending muscle movement commands only.
- Autonomic: These nerves control the automatic functions of the organs and systems in your body. Your autonomic nerves often involve mixed nerve fibers, some of which carry commands from your brain to their destination, and others that carry information about an organ’s function back to your brain.
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How does the peripheral nerve system help with other organs?
Your autonomic nervous system, which is a part of your peripheral nervous system, helps your brain control all of the vital organs in your body. That also helps your brain care for itself. An example of this is your brain controlling your heartbeat, which ensures your heart pumps blood to your body and brain. Without that blood flow, your brain would die in minutes.
Your peripheral nervous system also relays nerve signals from those organs to your brain. Examples include feeling warmth inside of your stomach when you drink a hot beverage or feeling full after a meal.
