| locus | <genetics> The site in a linkage map or on a chromosome where the gene for a particular trait is located. Any one of the alleles of a gene may be present at this site. (18 Nov 1997) |
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| locus ceruleus | A shallow depression, of a blue colour in the fresh brain, lying laterally in the most rostral portion of the rhomboidal fossa near the cerebral aqueduct; it lies near the lateral wall of the fourth ventricle and consists of about 20,000 melanin-pigmented neuronal cell bodies whose norepinephrine-containing axons have a remarkably wide distribution in the cerebellum as well as in the hypothalamus and cerebral cortex. Synonym: substantia ferruginea, locus cinereus, locus ferrugineus. (05 Mar 2000) |
| locus cinereus | A shallow depression, of a blue colour in the fresh brain, lying laterally in the most rostral portion of the rhomboidal fossa near the cerebral aqueduct; it lies near the lateral wall of the fourth ventricle and consists of about 20,000 melanin-pigmented neuronal cell bodies whose norepinephrine-containing axons have a remarkably wide distribution in the cerebellum as well as in the hypothalamus and cerebral cortex. Synonym: substantia ferruginea, locus cinereus, locus ferrugineus. (05 Mar 2000) |
| locus coeruleus | Bluish region in the superior angle of the fourth ventricle floor, corresponding to melanin-like pigmented nerve cells which lie lateral to the ponto-mesencephalic central gray (griseum centrale). It is also known as nucleus pigmentosus pontis, locus cinereus, and locus ferrugineus. (12 Dec 1998) |
| locus control region | A regulatory region first identified in the human beta-globin locus but subsequently found in other loci. The region is believed to regulate transcription by opening and remodeling chromatin structure. It may also have enhancer activity. (12 Dec 1998) |
| locus ferrugineus | A shallow depression, of a blue colour in the fresh brain, lying laterally in the most rostral portion of the rhomboidal fossa near the cerebral aqueduct; it lies near the lateral wall of the fourth ventricle and consists of about 20,000 melanin-pigmented neuronal cell bodies whose norepinephrine-containing axons have a remarkably wide distribution in the cerebellum as well as in the hypothalamus and cerebral cortex. Synonym: substantia ferruginea, locus cinereus, locus ferrugineus. (05 Mar 2000) |
| locus minoris resistentiae | A place of less resistance, in latin. For example, a damaged heart valve may act as a locus minoris resistentiae where bacteria released into the blood stream (bacteraemia) tend to settle. (12 Dec 1998) |
| locus of control | A theoretical construct designed to assess a person's perceived control over his/her own behaviour; classified as internal if the person feels in control of events, external if others are perceived to have that control. (05 Mar 2000) |
| locus perforatus anticus | A region at the base of the brain through which numerous small branches of the anterior and middle cerebral arteries (lenticulostriate arteries) enter the depth of the cerebral hemisphere; it is bordered medially by the optic chasm and anterior half of the optic tract, rostrally and laterally by the lateral olfactory stria; its anteromedial part corresponds to the olfactory tubercle. Synonym: substantia perforata anterior, locus perforatus anticus, olfactory area. (05 Mar 2000) |
| locus perforatus posticus | The bottom of the interpeduncular fossa at the base of the midbrain, extending from the anterior border of the pons forward to the mamillary bodies, and containing numerous openings for the passage of perforating branches of the posterior cerebral arteries. Synonym: substantia perforata posterior, locus perforatus posticus, Malacarne's space. (05 Mar 2000) |