| nucleus niger | A large cell mass, crescentic on transverse section, extending forward over the dorsal surface of the crus cerebri from the rostral border of the pons into the subthalamic region; it is composed of a dorsal stratum of closely spaced pigmented (i.e., melanin-containing) cells, the pars compacta, and a larger ventral region of widely scattered cells, the pars reticulata; the pars compacta in particular includes numerous cells that project forward to the striatum (caudate nucleus and putamen) and contain dopamine, which acts as the transmitter substance at their synaptic endings; other, apparently non-dopaminergic cells of the substantia nigra project to a rostral part of the ventral nucleus of thalmus, the middle layers of the superior colliculus and to restricted parts of the reticular formation of the midbrain; the nigrostriatal projection is reciprocated by a massive striatonigral fibre system with multiple neurotransmitters, chief among which is gamma-aminobutyric acid (GABA); substantia n. Receives smaller afferent projections from the subthalamic nucleus, the lateral segment of the globus pallidus, the dorsal nucleus of the raphe and the pedunculopontine nucleus of the midbrain. The pars reticulata forms part of the output system for the striate body. The substantia n. Is involved in the metabolic disturbances associated with Parkinson's disease and Huntington's disease. Synonym: locus niger, nucleus niger, Soemmerring's ganglion. (05 Mar 2000) |
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| nucleus of cuneate fasciculus | The larger Burdach's nucleus; one of the three nuclei of the posterior column of the spinal cord; located near the dorsal surface of the medulla oblongata at and below the level of the obex, the nucleus receives posterior root fibres corresponding to the sensory innervation of the arm and hand of the same side; together with its medial companion, the gracile nucleus, it is the major source of origin of the medial lemniscus. Synonym: nucleus cuneatus, Burdach's nucleus, nucleus funiculi cuneati, nucleus of cuneate fasciculus. (05 Mar 2000) |
| nucleus of Darkschewitsch | An ovoid cell group in the ventral central gray substance rostral to the oculomotor nucleus, receiving fibres from the vestibular nuclei by way of the medial longitudinal fasciculus; projections are not known, although some cross in the posterior commissure. (05 Mar 2000) |
| nucleus of Goll | The medial one of the three nuclei of the dorsal column, the remaining two being the cuneate nucleus and the accessory cuneate nucleus, which corresponds to the clava; it receives dorsal-root fibres conveying sensory innervation of the leg, and lower trunk, and projects, by way of the medial lemniscus, to the ventral nucleus posterior nucleus of the thalamus. Synonym: nucleus gracilis, nucleus fasciculi gracilis, nucleus funiculi gracilis, nucleus of Goll. (05 Mar 2000) |
| nucleus of inferior colliculus | The nerve cell groups composing the colliculus inferior. Synonym: nucleus colliculi inferioris. (05 Mar 2000) |
| nucleus of lateral geniculate body | Nucleus of the thalamus characterised by six layers of cells, two parvicellular, four magnocellular, alternating with thin layers of fibres; receives bilateral visual input, projects to calcarine cortex. (05 Mar 2000) |
| nucleus of lateral lemniscus | A substantial cell mass embedded in the lateral lemniscus, immediately below the latter's entry into the inferior colliculus; the nucleus represents a synaptic way-station for part of the fibres of the lateral lemniscus. Synonym: nucleus lemnisci lateralis. (05 Mar 2000) |
| nucleus of lens | The core or inner dense portion of the lens of the eye. Synonym: nucleus of lens. (05 Mar 2000) |
| nucleus of Luys | A circumscript nucleus, shaped like a biconvex lens, located in the ventral part of the subthalamus on the dorsal surface of the peduncular part of the internal capsule immediately rostral to the substantia nigra. The nucleus receives a massive topographic projection from the lateral segment of the globus pallidus, and a somatopically organised projection from the ipsilateral motor cortex; a smaller bundle of afferents from the centromedian nucleus of the thalamus terminate in the rostral part of the nucleus The subthalamic nucleus projects to both pallidal segments, to the pars reticulata of the substantia nigra, and in a small way to the ipsilateral pedunculopontine nucleus. Synonym: nucleus subthalamicus, corpus luysi, Luys' body, nucleus of Luys. (05 Mar 2000) |
| nucleus of medial geniculate body | The nerve cell groups composing the medial geniculate body (corpus geniculatum mediale). Synonym: nucleus corporis geniculati medialis. (05 Mar 2000) |
| nucleus of solitary tract | A slender cell column extending sagittally through the dorsal part of the medulla oblongata, beneath the floor of the rhomboid fossa, immediately lateral to the limiting sulcus. It is the visceral sensory (visceral afferent) nucleus of the brainstem, receiving the afferent fibres of the vagus, glossopharyngeal, and facial nerves by way of the solitary tract. The caudal two-thirds of the nucleus processes impulses originating in the pharynx, larynx, intestinal and respiratory tracts, and heart and large blood vessels; its rostral one-third receives impulses from the taste buds and is known as the rhombencephalic gustatory nucleus. Synonym: nucleus tractus solitarii. (05 Mar 2000) |
| nucleus of the mamillary body | A single large-celled lateral nucleus and a larger bipartite medial nucleus together comprising the mamillary body; present in the caudal hypothalamus. Synonym: nuclei corporis mamillaris, nucleus of the mamillary body. (05 Mar 2000) |
| nucleus olivaris | A large aggregate of small densely packed nerve cells arranged in folded laminae shaped like a purse with the opening (hilum) directed medially. It corresponds in position to the oliva, projects to all parts of the contralateral half of the cerebellar cortex by way of the olivocerebellar tract, and is the only source of cerebellar climbing fibres. Its afferent connections include fibres from the spinal cord, the dentate nucleus and motor cortex, but its major input appears to be the central tegmental tract originating from multiple nuclei at midbrain levels. Synonym: nucleus olivaris. (05 Mar 2000) |
| nucleus olivaris accessorius dorsalis | A detached part of the olivary nucleus dorsal to the latter's main body. Synonym: nucleus olivaris accessorius dorsalis. (05 Mar 2000) |
| nucleus olivaris accessorius medialis | A detached part of the olivary nucleus medial to the latter's main body, against the lateral side of the medial lemniscus and pyramidal tract. Synonym: nucleus olivaris accessorius medialis. (05 Mar 2000) |