Editing Nervous system (section)

====Arthropods====
[[File:Spider internal anatomy-en.svg|thumb|right|250px|Internal anatomy of a spider, showing the nervous system in blue]]

[[Arthropod]]s, such as [[insect]]s and [[crustacean]]s, have a nervous system made up of a series of [[ganglion|ganglia]], connected by a [[ventral nerve cord]] made up of two parallel connectives running along the length of the [[Abdomen|belly]].<ref name=Chapman>{{Cite book |title=The insects: structure and function |author=Chapman RF |publisher=Cambridge University Press |year=1998 |isbn=978-0-521-57890-5 |chapter=Ch. 20: Nervous system |pages=[https://archive.org/details/insectsstructure0000chap/page/533 533–568] |chapter-url=https://archive.org/details/insectsstructure0000chap/page/533}}</ref> Typically, each body segment has one [[ganglion]] on each side, though some ganglia are fused to form the brain and other large ganglia. The head segment contains the brain, also known as the [[supraesophageal ganglion]]. In the [[Insect#Nervous system|insect nervous system]], the brain is anatomically divided into the [[protocerebrum]], [[deutocerebrum]], and [[tritocerebrum]]. Immediately behind the brain is the [[subesophageal ganglion]], which is composed of three pairs of fused ganglia. It controls the [[Arthropod mouthparts|mouthparts]], the [[salivary glands]] and certain [[muscle]]s. Many arthropods have well-developed [[sense|sensory]] organs, including [[compound eye]]s for vision and [[antenna (biology)|antennae]] for [[olfaction]] and [[pheromone]] sensation. The sensory information from these organs is processed by the brain.

In insects, many neurons have cell bodies that are positioned at the edge of the brain and are electrically passive—the cell bodies serve only to provide metabolic support and do not participate in signalling. A protoplasmic fiber runs from the cell body and branches profusely, with some parts transmitting signals and other parts receiving signals. Thus, most parts of the [[insect brain]] have passive cell bodies arranged around the periphery, while the neural signal processing takes place in a tangle of protoplasmic fibers called [[neuropil]], in the interior.<ref>Chapman, p. 546</ref>