| accelerans | 1. Accelerating. 2. Obsolete term for an accelerator (sympathetic) nerve to the heart. Origin: L. Accelerator (05 Mar 2000) |
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| accelerant | 1. Anything that increases rapidity of action or function. 2. In physiology, a nerve, muscle, or substance that quickens movement or response. 3. A catalytic agent used to hasten a chemical reaction. 4. In nuclear physics, a device that accelerates charged particles (e.g., protons) to high speed in order to produce nuclear reactions in a target, often for the production of radionuclides or for radiation therapy. Synonym: accelerant. Origin: L. Accelerans, pres. P. Of ac-celero, to hasten, fr. Celer, swift (05 Mar 2000) |
| accelerate | 1. To cause to move faster; to quicken the motion of; to add to the speed of; opposed to retard. 2. To quicken the natural or ordinary progression or process of; as, to accelerate the growth of a plant, the increase of wealth, etc. 3. To hasten, as the occurence of an event; as, to accelerate our departure. <mechanics> Accelerated motion, motion with a continually increasing velocity. Accelerating force, the force which causes accelerated motion. (Nichol) Synonym: To hasten, expedite, quicken, dispatch, forward, advance, further. Origin: L. Acceleratus, p. P. Of accelerare; ad + celerare to hasten; celer quick. See Celerity. Source: Websters Dictionary (01 Mar 1998) |
| accelerated conduction | Any pathologically increased speed of conduction; usually occurs between the atrium and ventricles as in the Wolff-Parkinson-White and Lown-Ganong-Levine syndromes; such accelerated pathways provide the bases for particular forms of reentry tachycardia. (05 Mar 2000) |
| accelerated hypertension | <cardiology> A severe form of acute hypertension that results in the abrupt rise in the blood pressure (diastolic pressure often over 120 mmHg). If left untreated, malignant hypertension can cause damage to the blood vessels in the eye, kidneys, brain and heart. Complications include stroke, heart attack, blindness and renal failure. Symptoms include headache, blurred vision, nausea, vomiting and lethargy. Neurologic symptoms are also a common finding. Malignant hypertension occurs more commonly in males, African Americans and those with a history for hypertension. (27 Sep 1997) |
| accelerated idioventricular rhythm | A transient and intermittent type of arrhythmia with episodes lasting from a few seconds to a minute which usually occurs in patients with acute myocardial infarction or with digitalis toxicity. Suppressive therapy is rarely necessary because the ventricular rate is generally less than 100 beats per minute. (12 Dec 1998) |
| accelerated phase of leukaemia | Refers to chronic myelogenous leukaemia that is progressing. The number of immature, abnormal white blood cells in the bone marrow and blood is higher than in the chronic phase, but not as high as in the blast phase. (12 Dec 1998) |
| accelerated reaction | A response occurring in a shorter time than expected; the cutaneous manifestations occurring during the period between the second and tenth day following smallpox vaccination; because it is intermediate between a primary reaction and an immediate reaction, it is regarded as evidence of some degree of resistance. Synonym: vaccinoid reaction. (05 Mar 2000) |
| accelerated rejection | A transplant rejection manifested in less than three days. (05 Mar 2000) |
| acceleration | The act of accelerating, or the state of being accelerated; increase of motion or action; as, a falling body moves toward the earth with an acceleration of velocity; opposed to retardation. "A period of social improvement, or of intellectual advancement, contains within itself a principle of acceleration." (I. <astronomy> Taylor) Acceleration of the moon, the increase of the moon's mean motion in its orbit, in consequence of which its period of revolution is now shorter than in ancient times. Acceleration and retardation of the tides. See Priming of the tides, under Priming. Diurnal acceleration of the fixed stars, the amount by which their apparent diurnal motion exceeds that of the sun, in consequence of which they daily come to the meridian of any place about three minutes fifty-six seconds of solar time earlier than on the day preceding. Acceleration of the planets, the increasing velocity of their motion, in proceeding from the apogee to the perigee of their orbits. Origin: L. Acceleratio: cf. F. Acceleration. Source: Websters Dictionary (01 Mar 1998) |
| acceleration phase | <cell biology, cell culture> A period of increasing growth before the log phase in a culture of microbes. After the culture is started on a medium, at first there is no growth (the lag phase) and then the microbes start to gradually grow (acceleration phase) until they reach a constant maximum rate of growth (log phase). (15 Jan 1998) |
| accelerator | 1. Anything that increases rapidity of action or function. 2. In physiology, a nerve, muscle, or substance that quickens movement or response. 3. A catalytic agent used to hasten a chemical reaction. 4. In nuclear physics, a device that accelerates charged particles (e.g., protons) to high speed in order to produce nuclear reactions in a target, often for the production of radionuclides or for radiation therapy. Synonym: accelerant. Origin: L. Accelerans, pres. P. Of ac-celero, to hasten, fr. Celer, swift (05 Mar 2000) |
| accelerator factor | <chemical> Heat- and storage-labile plasma glycoprotein which accelerates the conversion of prothrombin to thrombin in blood coagulation. Factor v accomplishes this by forming a complex with factor xa, phospholipid, and calcium (prothrombinase complex). Deficiency of factor v leads to owren's disease. Chemical name: Blood-coagulation factor V (12 Dec 1998) |
| accelerator fibres | Postganglionic sympathetic nerve fibre's originating in the superior, middle, and inferior cervical ganglia of the sympathetic trunk, conveying nervous impulses to the heart that increase the rapidity and force of the cardiac pulsations. Synonym: augmentor fibres. (05 Mar 2000) |
| accelerator globulin | Globulin in serum that promotes the conversion of prothrombin to thrombin in the presence of thromboplastin and ionised calcium. See: factor Va, factor V, serum accelerator globulin. (05 Mar 2000) |