| redox system | <enzyme> An enzyme system in the tissues by which oxidation and reduction proceed simultaneously through the transference of hydrogen or of one or more electrons from one metabolite to another. See: oxidation-reduction. Synonym: redox system. (05 Mar 2000) |
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| vestibular system | <anatomy> The organ of the inner ear containing several three semicircular ducts at right angles to one another, helps keep the body balanced. (09 Oct 1997) |
| caudal neurosecretory system | urohypophysis |
| glandular system | All the glands of the body collectively. (05 Mar 2000) |
| visceral nervous system | <anatomy> Neurons that are not under conscious control, comprising two antagonistic components, the sympathetic and parasympathetic nervous systems. The autonomic nervous system regulates key functions including the activity of the cardiac (heart) muscle, smooth muscles (e.g., of the gut), and glands. The autonomic nervous system has two divisions: 1. The sympathetic nervous system that accelerates the heart rate, constricts blood vessels, and raises blood pressure. 2. The parasympathetic nervous system slows the heart rate, increases intestinal and gland activity, and relaxes sphincter muscles. (03 Jul 1999) |
| reminder system | <psychology> Systems used to prompt or aid the memory. The systems can be computerised reminders, colour coding, telephone calls, or devices such as letters and postcards. (12 Dec 1998) |
| cell-free system | <cell culture, molecular biology> Any system in which a normal cellular reaction is reconstituted in the absence of cells for example in vitro translation systems that will synthesise protein from mRNA using a lysate of rabbit reticulocytes or wheat germ. A fractionated cell extract that maintains a biological function. A subcellular fraction isolated by ultracentrifugation or other separation techniques must first be isolated so that a process can be studied free from all of the complex side reactions that occur in a cell. The cell-free system is therefore widely used in cell biology. (12 Dec 1998) |
| renal portal system | An arterial portal system, in which efferent glomerular arterioles receive blood from the capillaries of the renal glomeruli and carry it to the peritubular capillary plexus surrounding the proximal and distal convoluted tubules. Synonym: hypothalamohypophysial portal system. (05 Mar 2000) |
| p blood-group system | A blood group related to the abo, lewis and I systems. at least five different erythrocyte antigens are possible, some very rare, others almost universal. Multiple alleles are involved in this blood group. (12 Dec 1998) |
| renin-angiotensin-aldosterone system | The hormones, renin, angiotensin, and aldosterone work together to regulate blood pressure. A sustained fall in blood pressure causes the kidney to release renin. This is converted to angiotensin in the circulation. Angiotensin then raises blood pressure directly by arteriolar constriction and stimulates adrenal gland to produce aldosterone which promotes sodium and water retention by kidney, such that blood volume and blood pressure increase. (05 Mar 2000) |
| renin-angiotensin system | <physiology> A system consisting of renin, angiotensin-converting enzyme, and angiotensin II. Renin, an enzyme produced in the kidney, acts on angiotensinogen, an alpha-2 globulin produced by the liver, forming angiotensin I. The converting enzyme contained in the lung acts on angiotensin I in the plasma converting it to angiotensin II, the most powerful directly pressor substance known. It causes contraction of the arteriolar smooth muscle and has other indirect actions mediated through the adrenal cortex. (25 Jun 1999) |
| centimeter-gram-second system | The scientific system of expressing the fundamental physical units of length, mass, and time, and those units derived from them, in centimeters, grams, and seconds; currently being replaced by the International System of Units based on the meter, kilogram, and second. (05 Mar 2000) |
| reproductive system | In women, the organs that are directly involved in producing eggs and in conceiving and carrying babies. (12 Dec 1998) |
| pedal system | Efferent fibres connecting the forebrain with more caudal structures. (05 Mar 2000) |
| central nervous system | <anatomy, neurology> Pertaining to the brain, cranial nerves and spinal cord. It does not include muscles or peripheral nerves. In invertebrates, the central nervous system is composed of the segmental ganglia of the ventral nerve cord together with the fused ganglia or brain at the anterior end. Acronym: CNS (12 Jan 1998) |