Alphabetical list

Ganglia ( G ; Galen, c173 ) : A ganglion is a recognizable aggregation of neurons (Waldeyer, 1891). There are marginal ganglia associated with invertebrate nerve nets, central ganglia associated with invertebrate central nerve cords, and peripheral ganglia in the invertebrate and vertebrate peripheral nervous system (Meckel, 1817). For vertebrates it has long been best practice to restrict the term ganglion (and terms derived from ganglion) to structures of the peripheral nervous system (Meckel, 1817). As Herrick wrote, "The term ‘ganglion' is also sometimes used for nuclei or centers within the brain…but this usage is objectionable, for the use of the word ganglion in vertebrate neurology should be restricted to collections of neurons outside the central nervous system, such as the ganglia of the cranial and spinal nerves and the sympathetic [autonomic] ganglia." (1915, p. 108). A prime example is the use of "basal ganglia" for cerebral nuclei (Swanson, 2000). Discovered and named in macrodissected adult mammals by Galen (c173; see translation by May , 1968, pp. 695-696). more details

Ganglionic ring : Synonym for nerve ring; see Bullock & Horridge (1965, p. 13). more details

Glia ( Virchow, 1846 ) : The so-called supporting cells (Hooke, 1665) of the nervous system (Monro, 1783) that are divided into four major embryonic lineages: astrocytes (including ependymal cells), oligodendrocytes, Schwann cells, and microglia. Virchow is usually given credit for discovering and naming glia (1846, pp. 247-248; also see Virchow, 1856). more details

Glial cells : Synonym for glia (Virchow, 1846). more details

Gray matter ( GM ; Meckel, 1817 ) : Since the 16th century the nervous system (Monro, 1783) has been divided more and more precisely into gray matter and white matter (Meckel, 1817) based on their appearance in freshly dissected material observed with the naked eye-topographic macroarchitecture of nervous system; since the 19th century this differentiation has been made at the histological (subsystems microarchitecture of nervous system) level. Gray matter is the nervous system compartment that consists of the cell bodies (Deiters, 1865) of neurons (Waldeyer, 1891); the cytoplasmic neuron extensions: axons (Kölliker, 1896), dendrites (His, 1889), and amacrine extensions; and synapses (Foster & Sherrington, 1897) between the neuron extensions-as well as glia (Virchow, 1846) and parts of the circulatory system: vascular cells. Neuropil (Waldeyer, 1891) refers to the gray matter compartment exclusive of cell bodies and vascular cells (blood vessels) and thus consists of the cytoplasmic extensions of neurons and glia, including synapses. There is often a fuzzy border of variable and difficult to measure width between white matter and gray matter. For early history see Clarke & O'Malley (1996, Ch. 10); for modern histological interpretation see Peters et al. (1991), Swanson (2003, pp. 60-66). The general term "nervous system gray matter" as defined here was probably first used by Meckel for macrodissected adult humans (1817, see English translation, 1832 vol. 2, pp. 152-154, 166-167); also see Herrick (1915, p. 108). more details

Gray matter nucleus : A term applied to many gray matter regions in the cerebrospinal axis (Meckel, 1817), usually though not always (e.g., the human dorsal lateral geniculate nucleus) when they have relatively clear borders and are nonlaminated. The first use of the term in this way was by Ludwig (1779, Fig. 2b, p. 36); the cell nucleus, a cytological feature, was named by Brown (1833, p. 710). more details

Gray matter region : A recognizable volume of gray matter (Meckel, 1817) in the nervous system (Monro, 1783) that is distinguished by a unique set of neuron types (Bota & Swanson, 2007) with a unique spatial distribution. The entire gray matter is regionalized and individual regions may contain white matter (Meckel, 1817), including axons-of-passage, which are axons (Kölliker, 1896) passing through without forming synapses (Foster & Sherrington, 1897). The traditional way to view regionalization is with a Nissl stain, whose interpretation is based on methods that identify neuron types (Bota & Swanson, 2007) and their spatial distribution; see Brodal (1981, p. 4), Swanson (2004, p. 8). Examples of gray matter regions include cerebral cortical areas, thalamic nuclei, and peripheral nervous system ganglia. As a complete set, gray matter regions can be arranged in various different ways, for example, topographic arrangement of gray matter regions and subsystems arrangement of gray matter regions. Older synonyms include gray mass (Meynert 1872, p. 651), gray matter mass (Meynert, 1872, p. 654). more details