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Peripheral nervous system | |
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![]() The human nervous system. Sky blue is PNS; yellow is CNS. | |
Identifiers | |
Acronym(s) | PNS |
MeSH | D017933 |
TA98 | A14.2.00.001 |
TA2 | 6129 |
FMA | 9093 |
Anatomical terms of neuroanatomy |
The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain and the spinal cord.[1] The main function of the PNS is to connect the CNS to the limbs and organs, essentially serving as a relay between the brain and spinal cord and the rest of the body.[2] Unlike the CNS, the PNS is not protected by the vertebral column and skull, or by the blood–brain barrier, which leaves it exposed to toxins.[3]
The peripheral nervous system can be divided into a somatic division and an autonomic division. Each of these can further be differentiated into a sensory and a motor sector.[4] In the somatic nervous system, the cranial nerves are part of the PNS with the exceptions of the olfactory nerve and epithelia and the optic nerve (cranial nerve II) along with the retina, which are considered parts of the central nervous system based on developmental origin. The second cranial nerve is not a true peripheral nerve but a tract of the diencephalon.[5] Cranial nerve ganglia, as with all ganglia, are part of the PNS.[6] The autonomic nervous system exerts involuntary control over smooth muscle and glands.[7]
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