Study Of Both Excitation Condution Of Muscle Strip Of Frog Heart And The Potential Distribution Of The Frog Heart In Liquid Media

At his time, Craib studied the waves he recorded from the isolated terrapin heart and muscle strip immersed in oxygenated Ringer?solution, and deduced that the heart and muscle stirp must be a source of electricity of the nature of an electrical doublet, then he put forward the doublet hypothesis. Einthoven suggested the heart muscle fibres should be considered as individual electrical units and a single fibre may constitutes an electrical unit and inferred that the phenomena of dipole of the heart are due to the synthesis effect of many doublets. Grant recorded the bipolarized distribution of the potential on the body surface based on the Wilson lead system. Dipole theory has been accepted by the most and used to explain process of electrocadio-activity and the formation of electrocardiogram(ECG). Transmission of excitation in the muscle strip has been regarded as the process of moving of doublets. Barker explain the ECG recorded with exploring electrodes at different position such as endocardium side, midpoint between endocardium and pericardium, and pericardium side, there should be appear three kind of waves such as negative deflection, positive-negative deflection and positive deflection according to doublet theory. Nobody question these explanation for years. We think that many experiments done by Craib frequently using heart or muscle strip of spontaneous beating and it was difficult to determine from where initial excitation beginning and how the excitation spread around, besides it was also not clear where the reference point placed, what the designing principle of the instrument was, and which of current or voltage was amplified, etc. Therefore we consider that the conclusion from Craib抯 experiment should be restudied. In this study, we observe the electrical activity inside heart muscle strip meanwhile we record -3- the potentials around the muscle strip immersed in different liquid media in order to provkfe experimental evidence in explaining electrical activity of the myocardium. A strip of ventricular muscle from anterior wall paralleling atrioventricular sulcus was cut and immersed in a plat full of Tyrode solution or distilled water. 1. Stimulating position: @:at one end or midway of endocardium side,: ?at one end or midway of pericardium side. 2. Reference point and grounding electrode:畆eference point at edge of the plat; @3reference point inside muscle strip; ? reference point on the surface of the strip. Grounding electrode is always placed at the edge of the plat. 3. Recording electrodes: ~7D penetrating into muscle strip lognitudinally; ?penetrating into muscle transversely ; ? recording electrodes are place on the surface of endoc&dium;~ recording electrodes are placed on the surface of peircardium; ? recording electrodes are placed some distance away from the strip. The results show that @Dwhen using the plat edge as reference point, all the waves recorded inside muscle strip are positive in both kind of lognitudinal and transverse penetrating, no transition waves showed in the middle of the muscle strip, whether endocardium or pericardium was stimulated, and whether the muscle strip was immersed in Tyrode?solution or in distilled water. ﹚hen using the plat edge as referen...