Editing Nervous system (section)

===Anatomy in vertebrates===<!-- This section is linked from [[Lupus erythematosus]] -->
[[File:Human nervous system flowchart.png|thumb|right|380px|Flowchart of the human nervous system]]
[[File:Visible Human head slice.jpg|thumb|right|Horizontal section of the head of an adult female human, showing skin, skull, and brain with [[gray matter]] (brown in this image) and underlying [[white matter]]]]{{See also|List of nerves of the human body|List of regions in the human brain}}

The nervous system of [[vertebrate]]s (including humans) is divided into the [[central nervous system]] (CNS) and the [[peripheral nervous system]] (PNS).<ref name=KandelCh17/>
The CNS is the major division, and consists of the [[brain]] and the [[spinal cord]].<ref name=KandelCh17/> The [[spinal canal]] contains the spinal cord, while the [[cranial cavity]] contains the brain. The CNS is enclosed and protected by the [[meninges]], a three-layered system of membranes, including a tough, leathery outer layer called the [[dura mater]]. The brain is also protected by the skull, and the spinal cord by the [[vertebra]]e.

The peripheral nervous system (PNS) is a collective term for the nervous system structures that do not lie within the CNS.<ref name=Gray233/> The large majority of the axon bundles called nerves are considered to belong to the PNS, even when the cell bodies of the neurons to which they belong reside within the brain or spinal cord. The PNS is divided into [[somatic nervous system|somatic]] and [[autonomic nervous system|visceral]] parts. The somatic part consists of the nerves that innervate the skin, joints, and muscles. The cell bodies of somatic sensory neurons lie in [[dorsal root ganglion|dorsal root ganglia]] of the spinal cord. The visceral part, also known as the autonomic nervous system, contains neurons that innervate the internal organs, blood vessels, and glands. The autonomic nervous system itself consists of two parts: the [[sympathetic nervous system]] and the [[parasympathetic nervous system]]. Some authors also include sensory neurons whose cell bodies lie in the periphery (for senses such as hearing) as part of the PNS; others, however, omit them.<ref name=Hubbardvii>{{Cite book |title=The peripheral nervous system |author=Hubbard JI |publisher=Plenum Press |year=1974 |page=vii |isbn=978-0-306-30764-5 |url=https://archive.org/details/peripheralnervou0000hubb |url-access=registration}}</ref>

The vertebrate nervous system can also be divided into areas called [[gray matter]] and [[white matter]].<ref name=Purves15/> Gray matter (which is only gray in preserved tissue, and is better described as pink or light brown in living tissue) contains a high proportion of cell bodies of neurons. White matter is composed mainly of [[myelin]]ated axons, and takes its color from the myelin. White matter includes all of the nerves, and much of the interior of the brain and spinal cord. Gray matter is found in clusters of neurons in the brain and spinal cord, and in cortical layers that line their surfaces. There is an anatomical convention that a cluster of neurons in the brain or spinal cord is called a [[nucleus (neuroanatomy)|nucleus]], whereas a cluster of neurons in the periphery is called a [[ganglion]].<ref name=DorlandsGanglion/> There are, however, a few exceptions to this rule, notably including the part of the forebrain called the [[basal ganglia]].<ref name=Afifi/>

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