Editing Central nervous system (section)

====Cranial nerves====
Apart from the spinal cord, there are also peripheral nerves of the PNS that synapse through intermediaries or [[Ganglion|ganglia]] directly on the CNS. These 12 nerves exist in the head and neck region and are called [[cranial nerves]]. Cranial nerves bring information to the CNS to and from the face, as well as to certain muscles (such as the [[trapezius muscle]], which is innervated by [[accessory nerve]]s<ref name="Moore's" /> as well as certain [[cervical spinal nerve]]s).<ref name="Moore's" />

Two pairs of cranial nerves; the [[olfactory nerve]]s and the [[optic nerve]]s<ref name="Purves 2000"/> are often considered structures of the CNS. This is because they do not synapse first on peripheral ganglia, but directly on CNS neurons. The olfactory epithelium is significant in that it consists of CNS tissue expressed in direct contact to the environment, allowing for administration of certain pharmaceuticals and drugs.
<ref name="Gizurarson S. 2012 566–582"/>

{{multiple image
| align       = left
| direction   = horizontal
| total_width = 640
| image1      = Periferal nerve myelination.jpg
| alt1        = Image showing the way Schwann cells myelinate periferal nerves.
| width1      = 822
| height1     = 232
| caption1    =
| image2      = Neuron with oligodendrocyte and myelin sheath.svg
| alt2        = A neuron of the CNS, myelinated by an oligodendrocyte
| width2      = 410
| height2     = 485
| caption2    =
| footer      = A peripheral nerve myelinated by [[Schwann cell]]s (left) and a CNS neuron myelinated by an [[oligodendrocyte]] (right)
}}{{clear left}}