Ventral nerve cord
Encyclopedia
The ventral nerve cord makes up the nervous system
of some phyla
of the invertebrate
s, particularly within the nematode
s, annelid
s and the arthropod
s. 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 chordate
s, 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 http://medical-dictionary.thefreedictionary.com/commissures. 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 insect
s.
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
of some phyla
Phylum
In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....
of the invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, particularly within the nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
s, annelid
Annelid
The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches...
s and the arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s. It usually consists of cerebral ganglia
Ganglion
In anatomy, a ganglion is a biological tissue mass, most commonly a mass of nerve cell bodies. Cells found in a ganglion are called ganglion cells, though this term is also sometimes used to refer specifically to retinal ganglion cells....
anteriorly with the nerve cords running down the ventral
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
("belly", as opposed to back) plane of the organism. This characteristic is important in qualifying the difference compared to the chordate
Chordate
Chordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...
s, which have a dorsal nerve cord
Dorsal nerve cord
The dorsal nerve cord is one of the embryonic features unique to chordates, along with a notochord, a post-anal tail 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...
.
Ventral nerve cords from anterior to posterior (the thoracic
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
and abdominal
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
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 http://medical-dictionary.thefreedictionary.com/commissures. The complete system bears some likeness to a rope ladder
Ladder
A ladder is a vertical or inclined set of rungs or steps. There are two types: rigid ladders that can be leaned against a vertical surface such as a wall, and rope ladders that are hung from the top. The vertical members of a rigid ladder are called stringers or stiles . Rigid ladders are usually...
. In some animals the bilateral ganglia are fused into a single large ganglion per segment. This characteristic is found mostly in the insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s.
See also
- Dorsal nerve cordDorsal nerve cordThe dorsal nerve cord is one of the embryonic features unique to chordates, along with a notochord, a post-anal tail 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...
in ChordateChordateChordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...
s - Nerve netNerve netA nerve net is a type of simple nervous system that is found in members of the cnidaria, ctenophora, and echinodermata phyla. Nerve nets consist of interconnected neurons lacking a brain or any form of cephalization. This nervous system allows cnidarians to respond to physical contact. They may...
in cnidariaCnidariaCnidaria is a phylum containing over 9,000 species of animals found exclusively in aquatic and mostly marine environments. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance,...
and echinodermata phyla - Protocerebrum
- Deutocerebrum
- Tritocerebrum