- 1. The act of transmitting or conveying certain forms of energy, such as heat, sound, or electricity, from one point to another, without evident movement in the conducting body. 2. The transmission of stimuli of various sorts by living protoplasm. [L. con- duco, pp. ductus, to lead, conduct]- aberrant ventricular c. abnormal intraventricular c. of a supraventricular beat, especially where surrounding beats are normally conducted. SYN: ventricular aberration.- accelerated c. any pathologically increased speed of c.; 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.- air c. in relation to hearing, the transmission of sound to the inner ear through the external auditory canal and the structures of the middle ear.- anterograde c. c. in the expected normal direction between any cardiac structures. SYN: antegrade c., forward c., orthograde c..- atrioventricular c. (AVC), AV c. forward c. of the cardiac impulse from atria to ventricles via the AV node or any bypass tract, represented in the electrocardiogram by the PR interval. PH c. time is from the onset of the P wave to the first high-frequency component of the His bundle electrogram (normally 119 ± 38 msec); A-H c. time is from the onset of the first high-frequency component of the atrial electrogram to the first high-frequency component of the His bundle electrogram (normally 92 ± 38 msec); P-A c. time is from the onset of the P wave to the onset of the atrial electrogram (normally 27 ± 18 msec).- avalanche c. the discharge of an impulse from a neuron into a large number of neurons of the same physiologic system, thus producing the liberation of a very large amount of nervous energy by a given stimulus.- bone c. in relation to hearing, the transmission of sound to the inner ear through vibrations applied to the bones of the skull. SYN: osteophony.- concealed c. c. of an impulse through a part of the heart without direct evidence of its presence in the electrocardiogram; c. is inferred only because of its influence on the subsequent cardiac cycle.- decremental c. impaired c. in a portion of a fiber because of progressively lessening response of the unexcited portion of the fiber to the action potential coming toward it; it is manifested by decreasing speed of c., amplitude of action potential, and extent of spread of the impulse.- delayed c. first-degree AV block. See atrioventricular block, intraventricular block, bundle-branch block.- forward c. SYN: anterograde c..- intraatrial c. c. of the cardiac impulse through the atrial myocardium, represented by the P wave in the electrocardiogram.- intraventricular c. c. of the cardiac impulse through the ventricular myocardium, represented by the QRS complex in the electrocardiogram. HR c. time is from the onset of the first high frequency component of the His bundle electrogram to the onset of the QRS complex of the surface electrocardiogram (normally 43 ± 12 msec); HV c. time is from the onset of the first high-frequency component of the His bundle electrogram to the onset of the ventricular electrogram (normally approximates the HR interval but may be a little shorter). SYN: ventricular c..- retrograde VA c. c. backward from the ventricles or from the AV node into and through the atria. SYN: retroconduction, ventriculoatrial c., VA c..- sinoventricular c. a rare form of c. of the sinus impulse during paralysis of the atrial muscle by hyperkalemia. The impulse leaves the sinus node and enters the internodal tracts rapidly achieving the junctional tissues but without inscribing a P wave due to the inactivation of the atrial muscle cells.- supernormal c. SYN: supranormal c..- supranormal c. transmission of an impulse during the brief period of the cardiac cycle when it would be expected to fail if it occurred outside this time interval; considered to be better than expected rather than better than normal. Cf.:supranormal excitability. SYN: supernormal c..
* * *con·duc·tion kən-'dək-shən n1 a) transmission through or by means of a conductor also the transfer of heat through matter by communication of kinetic energy from particle to particle with no net displacement of the particlesb) CONDUCTIVITY2) the transmission of excitation through living tissue and esp. nervous tissue <\conduction of impulses to the brain>
* * *con·duc·tion (kən-dukґshən) the transfer of sound waves, heat, nervous impulses, or electricity; see also under system.
Medical dictionary. 2011.