| electrical coupling | <physiology> General term for an intimate cytoplasmic contact, mediated by gap junctions, between touching cells, such that electrical current injected into either cell changes the membrane potential of both. In neurons, arrays of gap junctions form electrical synapses, that allow action potentials to pass directly between cells. However, electrical coupling is not confined to excitable cells: many embryonic and adult epithelia are coupled, possibly to allow metabolic cooperation. (18 Nov 1997) |
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| electromagnetic coupling | <physics> A means of extracting energy from a magnetically confined plasma, where the plasma expands and pushes on the confining magnetic field, causing electrical energy to be generated in the external field-generating circuits. (09 Oct 1997) |
| energy coupling | <chemistry> The tranfer of energy produced in one reaction to another. (09 Oct 1997) |
| excitation contraction coupling | <physiology> Name given to the chain of processes coupling excitation of a muscle by the arrival of a nervous impulse at the motor end plate to the contraction of the filaments of the sarcomere. The crucial link is the release of calcium from the sarcoplasmic reticulum and the analogy is often drawn between this and stimulus secretion coupling, that also involves calcium release into the cytoplasm. (18 Nov 1997) |
| fixed coupling | Where several premature beats are seen, the interval between each of them and the preceding normal beat is constant. Synonym: constant coupling. Variable coupling, where several extrasystoles are seen, the interval between each of them and the preceding sinus beat varies. (05 Mar 2000) |
| specific dynamic action | The increase of heat production caused by the ingestion of food, especially of protein. (05 Mar 2000) |
| dynamic aorta | Abnormally marked pulsations of aorta. (05 Mar 2000) |
| dynamic compliance of lung | The value obtained when lung compliance is estimated during breathing by dividing the tidal volume by the difference in instantaneous transpulmonary pressures at the ends of the respiratory excursions, when flow in the airway is momentarily zero; this value deviates markedly from static compliance in patients in whom resistances and compliances are not uniform throughout the lung (i.e., uneven time constants). (05 Mar 2000) |
| dynamic computed tomography | Computed tomography with rapid injection of contrast medium, usually with sequential scans at only one or a few levels; used to enhance the vascular compartment. Synonym: dynamic CT. (05 Mar 2000) |
| dynamic CT | Computed tomography with rapid injection of contrast medium, usually with sequential scans at only one or a few levels; used to enhance the vascular compartment. Synonym: dynamic CT. (05 Mar 2000) |
| dynamic demography | A study of the functioning of a community, including statistical records. (05 Mar 2000) |
| dynamic disease | A physical disorder with no known or detectable organic basis to explain the symptoms. See: behaviour disorder, neurosis. Synonym: dynamic disease, functional disease, functional illness. (05 Mar 2000) |
| dynamic equilibrium | Balance A condition in which no further net change is occuring in a system, and free energy is minimimal. (09 Oct 1997) |
| dynamic focusing | <microscopy> An automatic focusing adjustment of the electron beam in high-quality cathode-ray or video image pickup tubes. The beam is made to land with the properly shaped minimum-sized spot regardless of its position in the raster scan (05 Aug 1998) |
| dynamic force | <radiobiology> Typically defined as the ability to do work. Power is the rate at which work is done, or the rate at which energy is changed. Work characterises the degree to which the properties of a substance are transformed. Energy exists in many forms, which can be converted from one to another in various ways. Examples include: gravitational energy, electrical energy, magnetic and electric field energy, atomic binding energy (a form of electrical energy really), nuclear binding energy, chemical energy (another form of electrical energy), in addition to these forms of potential energy there are also kinetic energy (energy due to motion), and thermal energy (heat, a form of kinetic energy where the motion is due to thermal vibrations/motions), and so on. (09 Oct 1997) |