The peripheral nervous system (PNS, or occasionally PeNS) 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. Unlike the CNS, the PNS is not protected by the bone of spine and skull, or by the blood–brain barrier, leaving 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. It is also a part of the nervous system.
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 eleven cranial nerve axons extend beyond the brain and are therefore considered part of the PNS.
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Famous quotes containing the words nervous system, system, peripheral and/or nervous:
“A car can massage organs which no masseur can reach. It is the one remedy for the disorders of the great sympathetic nervous system.”
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“If we are to change our world view, images have to change. The artist now has a very important job to do. Hes not a little peripheral figure entertaining rich people, hes really needed.”
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“I cant accept our nervous age, since mankind has been nervous during every age. Whoever fears nervousness should turn into a sturgeon or smelt; if a sturgeon makes a stupid mistake, it can only be one: to end up on a hook, and then in a pan in a pastry shell.”
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