The peripheral nervous system forms the connection between the central nervous system and the muscles and senses. It ensures that information from the organs, senses and muscles gets to the central nervous system and that commands from the central nervous system can travel the opposite way.
The peripheral nervous system is divided into the autonomic nervous system and the somatic nervous system. This is a functional division; there is no real anatomical distinction.
The autonomic nervous system controls the smooth muscles, the heart, and various organs. It regulates the ins and outs of the body. We have no control over this part of the nervous system; it is mainly involved in automatic processes and reflexes. The autonomic nervous system can again be divided into the sympathetic and parasympathetic nervous systems. The sympathetic system is especially active when we are active, for example in stressful situations. It then ensures that the heart rate goes up, that the digestive system is temporarily shut down, that a lot of blood goes to the muscles and that the body is ready for action ("fight or flight" ). The parasympathetic nervous system does the opposite. It causes the heart rate to slow down, digestion to begin, and energy to be stored. So it is active when we are relaxed.
The part of the peripheral nervous system that we do have control over is the somatic nervous system. This part controls the skeletal muscles and ensures that we can walk, play soccer, talk; in short it is there for the interaction with our environment. This does not mean, however, that we are always aware of these processes. Walking, for example, is an automated action, which usually does not require us to think.
Author: Bart Aben (translated by Melanie Smekal)