Nerve cord

Nerve cord may refer to the following structures:

• in invertebrates, it refers to the ventral nerve cord, whereas
• in chordates, it stands for the dorsal nerve cord.

The ventral nerve cord makes up the nervous system of some phyla of the invertebrates, particularly within the nematodes, annelids and the arthropods. It usually consists of cerebral ganglia anteriorly with the nerve cords running down the ventral ("belly", as opposed to back) plane of the organism. This characteristic is important in qualifying the difference compared to the chordates, which have a dorsal nerve cord.

Ventral nerve cords from anterior to posterior (the thoracic and abdominal tagma in the arthropods) are made up of segmented ganglia that are connected by a tract of nerve fibers passing from one side to the other of the nerve cord called commissures [1]. The complete system bears some likeness to a rope ladder. In some animals the bilateral ganglia are fused into a single large ganglion per segment. This characteristic is found mostly in the insects.

The dorsal nerve cord is one of the embryonic features unique to chordates, along with a notochord, a post-anal tail, an endostyle, and pharyngeal slits. The dorsal nerve cord is a hollow cord dorsal to the notochord. It is formed from a part of the ectoderm that rolls, forming the hollow tube, compared to other animal phyla, which have solid, ventral tubes. The dorsal nerve cord is later modified in vertebrates into the central nervous system which is composed of the brain and spinal cord. Dorsal nerve cord is mainly found in subphylum Vertebrata.

Dorsal means the "back" side, as opposed to Ventral which is the "front" side of an organism. In organisms with Bipedalism dorsal is the back and ventral is the front. In organisms which walk on four limbs the dorsal surface is the top (back) and the ventral surface is the bottom (belly).

See also

• ventral nerve cord in arthropods
• nerve net in cnidaria and echinodermata phyla

See also

• Dorsal nerve cord in Chordates
• Nerve net in cnidaria and echinodermata phyla
• Protocerebrum
• Deutocerebrum
• Tritocerebrum

References

ISBN links support NWE through referral fees

• Hickman, Cleveland and Roberts L. Keen S. Larson A. Eisenhour D. Animal Diversity, 4th, New York: McGraw Hill. ISBN 978-0-07-252844-2. 

External links

• Comparison of spinal cord and ventral nerve cord
• Nervous system of a lobster
• Insect morphology

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

• Nerve_cord  ^history
• Ventral_nerve_cord  ^history
• Dorsal_nerve_cord  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Nerve cord"

Note: Some restrictions may apply to use of individual images which are separately licensed.