Editing Nerve (section)

===Categories===
Nerves are categorized into three groups based on the direction that signals are conducted:

* [[Afferent nerve fiber|Afferent nerve]]s conduct sensory information from [[sensory neuron]]s to the [[central nervous system]], for example from the [[mechanoreceptors]] in [[skin]]. Bundles of afferent fibers are known as ''sensory nerves''.<ref name="Purves" /><ref name="Marieb" />
* [[Efferent nerve fiber|Efferent nerve]]s conduct signals from the central nervous system along [[motor neuron]]s to their target [[muscle]]s and [[gland]]s. Bundles of these fibres are known as ''efferent nerves.''
* [[Mixed nerve]]s contain both afferent and efferent axons, and thus conduct both incoming [[sense|sensory]] information and outgoing muscle commands in the same bundle. All spinal nerves are mixed nerves, and some of the cranial nerves are also mixed nerves.
Nerves can be categorized into two groups based on where they connect to the central nervous system:
* [[Spinal nerve]]s innervate (distribute to/stimulate) much of the body, and connect through the [[vertebral column]] to the [[spinal cord]] and thus to the [[central nervous system]]. They are given letter-number designations according to the [[vertebra]] through which they connect to the spinal column.
* [[Cranial nerves]] innervate parts of the head, and connect directly to the [[brain]] (especially to the [[brainstem]]). They are typically assigned [[Roman numerals]] from 1 to 12, although [[cranial nerve zero]] is sometimes included. In addition, cranial nerves have descriptive names.