| 释义 |
nerve cord
nerve′ cord`
n. 1. the hollow dorsal tract of nervous tissue that constitutes the central nervous system of all chordates and that developed as the spinal cord and brain of vertebrates. 2. a double strand of nerve fibers in elongate invertebrates, as earthworms, that connects with a pair of nerve ganglia at each body segment. [1875–80] Nerve Cord
nerve cord[′nərv ‚kȯrd] (invertebrate zoology) Paired, ventral cords of nervous tissue in certain invertebrates, such as insects or the earthworm. (zoology) Dorsal, hollow tubular cord of nervous tissue in chordates. Nerve Cord a structure within the central nervous system of annelids and arthropods. The nerve cord is situated on the ventral side of the body, under the gut. It is connected to the cerebral ganglia. The nerve cord consists of a pair of partially fused longitudinal nerve trunks, called connectives, and of pairs of segmental ganglia that innervate each of the body segments. The primitive form of the nerve cord, which occurs in some primitive annelids, polychaetes, and onychophorans, is scaliform, having widely spaced trunks and long commissures between the ganglia. nerve cord
nerve cord a strand of nervous tissue that forms part of the CENTRAL NERVOUS SYSTEM of invertebrates. |