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 . 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.
Famous quotes containing the words nerve and/or cord:
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—Billy Wilder (b. 1906)
“Two are better than one; because they have a good reward for their labour. For if they fall, the one will lift up his fellow: but woe to him that is alone when he falleth; for he hath not another to help him up. Again, if two lie together, then they have heat: but how can one be warm alone? And if one prevail against him, two shall withstand him; and a threefold cord is not quickly broken.”
—Bible: Hebrew Ecclesiastes, 4:9-12.