| germinal vesicle | The nucleus of a primary oocyte, the development of which is suspended in prophase I of the first meiotic division between embryohood and sexual maturity. (09 Oct 1997) |
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| active centre | The part of a macromolecule at which a substrate or ligand, upon binding, produces biological activity; for an enzyme, this is the catalytic centre, the site on an enzyme that catalyses the reaction. (05 Mar 2000) |
| anospinal centre | The centre in the spinal cord that controls the contraction of the anal sphincter. (05 Mar 2000) |
| asymmetric centre | <chemistry> Same as a chiral centre, a tetrahedral carbon atom that bears four different substituents. (09 Jan 1998) |
| Broca's centre | The posterior part of the inferior frontal gyrus of the left or dominant hemisphere, corresponding approximately to Brodmann's area 44; Broca identified this region as an essential component of the motor mechanisms governing articulated speech. Synonym: Broca's area, Broca's field, motor speech centre. (05 Mar 2000) |
| Budge's centre | The preganglionic motor neurons in the first thoracic segment of the spinal cord which give rise to the sympathetic innervation of the dilator muscle of the eye's pupil. Synonym: Budge's centre. (05 Mar 2000) |
| vasomotor centre | Diffuse area of the reticular formation in the lateral medulla containing neurons that control vascular tone; consists of separate vasodepressor and vasopressor areas. (05 Mar 2000) |
| reaction centre | <plant biology> The site in the chloroplast that receives the energy trapped by chlorophyll and accessory pigments and initiates the electron transfer process. A photosynthetic complex containing chlorophyll (or bacteriochlorophyll) and other components, within which occurs the initial electron transfer reactions of photophosphorylation. (09 Oct 1997) |
| catalytic centre | See: active centre. (05 Mar 2000) |
| cell centre | Microtubule organising centre of the cell, the pericentriolar region. (18 Nov 1997) |
| vital centre | Centre essential to life; usually refers to the centres located in the medulla oblongata which are necessary for the maintenance of respiration and circulation. (05 Mar 2000) |
| medullary centre | The great mass of white matter composing the interior of the cerebral hemisphere; the name refers to the general shape of this white core in horizontal sections of the hemisphere. Synonym: centrum medullare, centrum ovale, medullary centre, semioval centre, Vicq d'Azyr's centrum semiovale, Vieussens' centrum. (05 Mar 2000) |
| centre | 1. The middle point of a body; loosely, the interior of a body. A centre of any kind, especially an anatomical centre. 2. A group of nerve cells governing a specific function. Synonym: centrum. Origin: L. Centrum; G. Kentron (05 Mar 2000) |
| centre median de Luys | Synonym: centromedian nucleus. Origin: Fr. (05 Mar 2000) |
| centre of ossification | The site of earliest bone formation via accumulation of osteoblasts within connective tissue (membranous ossification) or of earliest destruction of cartilage prior to onset of ossification (endochondral ossification). Synonym: punctum ossificationis, ossific centre, point of ossification. (05 Mar 2000) |