Alphabetical list

Nerve cell : Synonym for neuron (Waldeyer, 1891). The term was used by Kölliker (1852; see Shepherd, 1991, p. 35); also see Peters et al. (1991, p. 11). more details

Nerve fiber ( nerves (Herophilus, c335-280 BC) ) : An unmyelinated axon or a myelinated axon; literally accurate for the peripheral nervous system, but often applied (ambiguously) to the central nervous system as well. In the second century Galen (see translations by Duckworth, 1962, p. 254; Clarke, 1968, p. 124) recognized the fibrous nature of nerves (Herophilus, c335-280 BC). Leeuwenhoek (1718; see Van der Loos, 1967, pp. 10-16) identified the nerve fiber itself as the ultimate structure of nerves and called it a vessel, whereas Ehrenberg (1833, pp. 453-456) called it a nerve fiber. more details

Nerve net : A topographic division that is a longitudinally arranged nervous system (Monro, 1783) with radial symmetry and relatively evenly and diffusely distributed neurons (Waldeyer, 1891), characteristic of Coelenterates, Ctenophores, Hemichordates, Pogonophores, and adult Echinoderms. While small neuron condensations (called marginal ganglia) and circular zones (called nerve rings) with a higher concentration of neurons and neuron extensions can be present, nerves (Herophilus, c335-280 BC) are not clearly differentiated, and nothing like a central nervous system (Meckel, 1817) is present; see Bullock & Horridge (1965, p. 12 & Ch. 8), Cobb (1995). It is thus a nervous system with no clear topographic divisions-a divisionless nervous system. The nervous system of hydra (a Coelenterate) is an example of a relatively simple diffuse nerve net, whereas the terminal plexuses in the wall of the mammalian digestive system can be viewed as analogous to a relatively differentiated nerve net. more details

Nerve ring : A topographic division consisting of a circular zone of a nerve net with a higher concentration of neurons (Waldeyer, 1891) and neuron extensions; see Bullock & Horridge (1965, p. 475), Cobb (1995, p. 411). more details

Nerve terminal ( Cajal, 1899 ) : Synonym for axon terminal (Barker, 1899); term used for Golgi material by Cajal (1899, p. 67). more details

Nerves ( n ; Herophilus, c335-280 BC ) : A nerve is a topographic division with macroscopically recognizable bundles of axons (Kölliker, 1896), or white matter tracts, in the peripheral nervous system (Meckel, 1817) of invertebrates and vertebrates. A nerve can have a number of structural differentiations like roots, trunk, and branches, and can have a peripheral ganglion associated with it. When a series of ganglia is associated with a white matter tract, it is referred to as a peripheral nerve cord in the peripheral nervous system (Meckel, 1817), a central nerve cord in the central nervous system (Meckel, 1817) of invertebrates, or a radial nerve cord in a nerve net of invertebrates. Herophilus (c335-c280 BC), the founder of human anatomy, is credited with discovering nerves, including most of the cranial nerves (Longet, 1842) and spinal nerves (Camper, 1760) by distinguishing them from arteries; see Solmsen (1961, p. 185), von Staden (1989, pp. 250-252), and Longrigg (1993, pp. 192, 211). more details

Nervous system ( NS ; Monro, 1783 ) : One system in the set of body systems. According to Bullock & Horridge, "A nervous system may be defined as an organized constellation of cells (neurons) specialized for the repeated conduction of an excited state from receptor sites or from other neurons to effectors or to other neurons." (1965, p. 6; also see Brusca & Brusca, 1990, p. 81). The structural arrangement or organization of connections between these neurons (Waldeyer, 1891), or more generally nodes, forms a neural network called the wiring diagram of the nervous system (Monro, 1783). In many animals the nervous system also contains glia (Virchow, 1846), and is invaded by the circulatory system. It is the chief system that integrates adjustments and reactions of the organism to internal and environmental conditions; see Dorland's (2003). In all animals the nervous system probably differentiates from the embryonic ectodermal layer; see Brusca & Brusca (1990, p. 103). The nervous system as such was probably first recognized (in writings that survive) by Rufus of Ephesus (fl. c100; see Clarke & O'Malley, 1996, p. 13); Monro (1783, p. 1) introduced the term as now used. more details

Nervous system ( Willis, 1664 ) : Willis's use of the term in his comparative anatomical research was synonymous with peripheral nervous system (Meckel, 1817); see Willis translation by Pordage (1681, p. 125ff.). more details

Nervous system parts : Objects in the nervous system (Monro, 1783) above the level of neuron types (Bota & Swanson, 2007). more details

Network : Short form of neural network. more details

Neural network : The structural arrangement of all neurons (Waldeyer, 1891) and their connections in a nervous system (Monro, 1783). A neural network has a set of nodes and the connections between them and other parts of the body like muscles and glands. A complete neural network can be distinguished from a neural subnetwork, which is an arbitrary subset of the complete neural network, often distinguished on functional grounds. more details

Neural plate ( NPL ; Stricker, 1860 ) : The medial differentiation of the embryonic vertebrate ectodermal layer, dorsal (Barclay, 1803) to the notochord, that goes on by the process of neurulation to form the neural tube (Baer, 1837); observed in macrodissected chick embryos by Malpighi (1673, Tab. I), and named thus by Stricker (1860, p. 474) based on toad embryo histology. more details

Neural subnetwork : An arbitrary subset of a complete neural network, often distinguished on functional grounds. A closely related term is neural subsystem. more details

Neural subsystem : A subset of the complete nervous system (Monro, 1783) defined on functional grounds; for example, the visual system or the somatic motor system. A closely related term is neural subnetwork, but formally a neural subsystem would include objects other than neurons (Waldeyer, 1891). more details

Neural tube ( NT ; Baer, 1837 ) : The embryonic primordium of the adult cerebrospinal axis (Meckel, 1817) that is formed from the neural plate (Stricker, 1860) by the process of neurulation; see Nieuwenhuys et al. (2008, pp. 7-9). Galen probably glimpsed the macrodissected mammalian neural tube (see Adelmann, 1966, p. 747) and Baer (1837, p. 59) introduced the term for macrodissected vertebrate embryos. Varolio (1573, see English translation, 1969, p. 34) observed three transparent globules (tres globulos transparentes in Latin) in the 9-day macrodissected chick embryo and Baer (1837, pp. 106, 107) called them the three primary brain vesicles (primären Hirnbläschen in German and Vesiculae cerebrales in Latin): anterior or forebrain primary vesicle (vordere Bläschen in German), middle or midbrain primary vesicle (mittleres Bläschen in German), and posterior or hindbrain primary vesicle (hinteres Bläschen in German). He also observed that they develop into 5 vesicles going on to form the 5 morphological elements or basic parts of the adult vertebrate brain (Cuvier, 1800): Vorderhirn, Zwischenhirn, Mittelhirn, Hinterhirn, and Nachhirn in the original German. Sharpey et al. (1867, p. 577) gave the English and Latin equivalents of these 5 parts: secondary forebrain or prosencephalon, interbrain or diencephalon, midbrain or mesencephalon, secondary hindbrain or epencephalon, and afterbrain or metencephalon. In the Foundational Model of Connectivity these 5 parts are called endbrain (Kuhlenbeck, 1927) or telencephalon (Kuhlenbeck, 1927), interbrain (Baer, 1837) or diencephalon (Sharpey et al., 1867), midbrain (Baer, 1837) or mesencephalon (Sharpey et al., 1867), hindbrain (Baer, 1837) or epencephalon (Sharpey et al., 1867), and afterbrain (Sharpey et al., 1967), metencephalon (Sharpey et al., 1867) or medulla (Winslow, 1733). The hindbrain (Baer, 1837) consists of cerebellum (Aristotle) and pons (Haller, 1747). more details

Neurite : Term often used now for a neuron extension when its identity as axon (Kölliker, 1896), dendrite (His, 1889), or amacrine extension is unclear; see Peters et al. (1976, p. 9; 1991, p. 10). The term was originally coined to refer to the axon by Rauber (1894). more details

Neuron ( Waldeyer, 1891 ) : For the nervous system (Monro, 1783), the basic structural and functional unit at the level of cells (Hooke, 1665). The connections of neurons form the connectome and wiring diagram. Probably discovered microscopically by Dutrochet (1824; Pl. 2, fig. 20) in unfixed molluscan ganglia (Galen, c173) and named thus by Waldeyer (1891, p. 1352); also see Peters et al. (1991, p. 11). more details

Neuron extension : A thin cytoplasmic projection from the cell body (Deiters, 1865) that may be axon (Kölliker, 1896), dendrite (His, 1889), or amacrine extension. Synonym is neuron process. more details

Neuron population ( POP ; Burns, 2001 ) : An arbitrarily defined set of neurons (Waldeyer, 1891) that may or may not correspond exactly to a specific gray matter region or neuron type (Bota & Swanson, 2007). For example, a neuron population is formed by a subset of the individual neurons that together constitute a neuron type. In contrast, however, all neurons within an anterograde pathway tracer injection site that spreads to involve multiple adjacent gray matter regions, or an irregular extent within a single gray matter region, form the neuron population associated with that injection site. Another example of this type would be all neurons within multiple gray matter regions that project to a single gray matter region-as demonstrated, for example, by a retrograde pathway tracer injection site. A third example would be all neurons in the hypothalamus (Kuhlenbeck, 1927) that express the corticotropin-releasing hormone (CRH) gene following hypovolemic stress, as demonstrated by in situ hybridization. In general, a site contains a neuron population. Term thus defined was introduced by Burns (2001, p. 1201 and Fig. 10). more details

Neuron process : Synonym for neuron extension. Use of neuron process is discouraged because process could easily be misinterpreted to mean an action or series of actions; see Oxford English Dictionary (1989). Purkinje (1838, e.g., Fig. 16) used the term process (Fortsätze in the original German) for extensions of neuron cell bodies (Deiters, 1865)-which he referred to as gangliöse körperchen, ganglionic bodies; see Barker (1899, p. 66), Jones & Cowan (1983, p. 290). "Process" has been used in anatomy to describe a protuberance or projection since at least the 16th century; see Oxford English Dictionary (1989, def. 13). more details

Neuron type ( Bota & Swanson, 2007 ) : For purposes of wiring diagrams, neuron types are defined and classified primarily by their connections and, secondarily by their location, shape, and size. Neurons (Waldeyer, 1991) can be placed in a seven-level taxonomic hierarchy, with neuron types occupying a level equivalent to species in animal taxonomy. Formally, a neuron type is defined as a distinct cluster in polythetic parametric space, with the main parameter being connections, secondary parameters being location, shape, and size, and tertiary parameters also helpful. An example of a neuron type is blue cone, of the neuron group cone, of the neuron class photoreceptor, of the neuron category visual, of the neuron division sensory, of the cell type neuron, with no known neuron varieties of this neuron type, at least in rat (see Bota & Swanson, 2007). Neuron types can consist of a single identified neuron (most common for invertebrates) or a set of neurons sharing the same parametric space. Neuron types were first recognized by Purkinje (1838) and first classified by Golgi (1873). more details

Neuropil ( nep ; Waldeyer, 1891 ) : The gray matter (Meckel, 1817) compartment exclusive of cell bodies (Deiters, 1865) and vascular cells, thus consisting of the cytoplasmic extensions of neurons (Waldeyer, 1891) and glia (Virchow, 1846), including synapses (Foster & Sherrington, 1897). It was discovered histologically in spiders by Leydig (1855, p. 413), who called it the Punktsubstanz, or dotted substance in English; Waldeyer first used the term (1891, p. 1354). Also see Bullock & Horridge (1965, pp. 16, 27, 54), Peters et al. (1991, Ch. 11). more details

Node : The site of origin or of termination of a connection at the level of a gray matter region (macronode), neuron type (Bota & Swanson, 2007) (mesonode), or individual neuron (Waldeyer, 1891) (micronode). Nodal masses of gray matter were described systematically as long ago as Meynert (1872, p. 654). more details

Nomenclature ( Bota & Swanson, 2010 ) : In the Foundational Model of Connectivity a set of terms that refers to a nervous system part. more details

Nucleus : See gray matter nucleus and cell nucleus (Brown, 1833). more details