Central nervous system

Definition

The condensed, integrative portion of the nervous system comprising the brain (supraesophageal ganglion) and the ventral nerve cord with its segmental ganglia, responsible for processing sensory input and coordinating motor output. In arthropods, the CNS consists of a dorsal brain connected by circumesophageal connectives to a ventral, ladder-like chain of ganglia; this organization contrasts with the diffuse nerve nets of cnidarians and the more centralized but differently arranged cords of annelids.

Etymology

Latin centralis (center) + nervus (nerve, sinew) + systema (organized whole)

Example

In a jumping spider (Salticidae), the central nervous system is dramatically enlarged: the subesophageal ganglion and optic ganglia occupy so much body space that they extend into the legs, enabling rapid visual processing and precise prey-capture strikes.

Synonyms

• CNS

Related Terms

• brain
• ganglion
• Ventral nerve cord
• peripheral nervous system
• supraesophageal ganglion
• Subesophageal ganglion
• circumesophageal connective
• neuroanatomy
• Stomatogastric nervous system

Usage Notes

In arthropod morphology, 'CNS' strictly denotes the brain and ventral nerve cord with their ganglia, excluding the stomatogastric (visceral) nervous system and peripheral sensory nerves. The term is sometimes used relatively: in some crustaceans and insects, ganglia may be fused or displaced, making the boundary between central and peripheral less distinct. Contrast with 'peripheral nervous system' (sensory neurons, motor neurons outside the CNS) and 'diffuse nervous system' (as in cnidarians). Capitalization as 'CNS' is standard in scientific writing after first use.