Peripheral nerve

The peripheral nervous system (PNS) is the part of the nervous system that consists of the nerves and ganglia outside of the brain and spinal cord.

The main function of the PNS is to connect the central nervous system (CNS) to the limbs and organs, essentially serving as a communication relay going back and forth between the brain and the extremities.

Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain barrier, which leaves it exposed to toxins and mechanical injuries. The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system; some textbooks also include sensory systems. The cranial nerves are part of the PNS with the exception of cranial nerve II, the optic nerve, along with the retina. The second cranial nerve is not a true peripheral nerve but a tract of the diencephalon.

Cranial nerve ganglia originate in the CNS. However, the remaining twelve cranial nerve axons extend beyond the brain and are therefore considered part of the PNS.

see Lower motor neuron

see Upper motor neuron.

see Median nerve

see Ulnar nerve.

see Peripheral nerve entrapment

see Peripheral nerve injury

see Peripheral nerve lesion

see Peripheral nerve regeneration.

see Peripheral nerve sheath.

see Peripheral nerve surgery

see Peripheral nerve tumor


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