Peripheral nervous system
The peripheral nervous system ( PNS ) is the part of the nervous system that is outside the brain and spinal cord . The latter form the central nervous system (CNS). In contrast to this, the PNS is not protected by bones or the blood-brain barrier . Both the CNS and the PNS are further divided into the somatic nervous system and the autonomic nervous system .
From a functional point of view, however, a rigid demarcation of the PNS from the CNS does not make sense. Nerve cells (neurons) always consist of a cell body ( soma ) and its extensions ( dendrites and axons ) around the cell nucleus . The motor (responsible for movement) and preganglionic vegetative (responsible for the function of the internal organs) neurons all have their soma in the CNS. The sensitive neurons (responsible for sensations), on the other hand, almost without exception have their soma in nerve nodes ( ganglia ) in the PNS itself, but almost all of their processes lead to the CNS, where the actual information processing takes place and conscious or unconscious ( reflexes ) reactions are triggered . The PNS does not exist as an independent system, but as a purely topographically demarcated department. The only exception to this is the intramural nervous system (nerves in the wall of internal organs), in which information processing is partly independent of the CNS.
The peripheral nervous system includes:
- Cranial nerves
- Spinal nerves (nerves from the spinal cord )
- enteric nervous system (abdominal brain)