Lexic.us

Definition of Locus niger

1. Noun. A layer of deeply pigmented grey matter in the midbrain; associated with the striate body; is involved in metabolic disturbances associated with Parkinson's disease and with Huntington's disease.

Medical Definition of Locus niger

1. 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)

Lexicographical Neighbors of Locus Niger

Literary usage of Locus niger

Below you will find example usage of this term as found in modern and/or classical literature:

1. The Encyclopaedia Britannica: A Dictionary of Arts, Sciences, and General by Thomas Spencer Baynes (1888)
"... of the cerebrum are the corpora striata, the optic thalami, the corpora geniculata, the corpora quadrigemina, and the locus niger in each crus cerebri. ..."

2. Lectures on the Diseases of the Spinal Cord by Jean Martin Charcot (1881)
"... locus niger and Red Nucleus of Stilling— 111 vision of Crusta iuto Three Segments.— The Pyramidal Segment at the Period of Birth. ..."

3. The Encyclopaedia Britannica: A Dictionary of Arts, Sciences and General (1890)
"Owing to the connections of the locus niger, nucleus caudatus, and Dudens lenticularis with the crusta, Meynert has named ..."

4. Anatomy, Descriptive and Surgical by Henry Gray (1883)
"In the interior of the crura is contained a mass of dark-gray matter, called locus niger. The third nerve may be seen emerging from the inner side of either ..."

5. The American Journal of the Medical Sciences by Southern Society for Clinical Investigation (U.S.) (1899)
"... agitans is due to a disease of the locus niger is not at all conclusive, since symptoms resembling somewhat those of paralysis agitans have occurred in ..."

6. A Text-book of physiology by Isaac Ott (1913)
"tain fibers coming from the gray matter of the medulla, pons, corpora quadrigemina, locus niger, and masses of gray matter lying in a line along the ..."

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