. The Biological bulletin. Biology; Zoology; Marine biology. TUNICATE CARDIOVASCULAR PHYSIOLOGY E. Electrical stimulation of the heart 445 Ipsilateral extrasystoles produced by electrical stimulation were followed by a compensatory pause. Electrical stimulation demonstrated a relative and absolute refractory period. It was possible to reverse both in situ and isolated hearts by stimulating the non-pacing arm of the heart. A pacemaker competition occurred when the post-stimulatory frequency of the newly active pacemaker was only slightly greater than the frequency of the previously active pacem
. The Biological bulletin. Biology; Zoology; Marine biology. TUNICATE CARDIOVASCULAR PHYSIOLOGY E. Electrical stimulation of the heart 445 Ipsilateral extrasystoles produced by electrical stimulation were followed by a compensatory pause. Electrical stimulation demonstrated a relative and absolute refractory period. It was possible to reverse both in situ and isolated hearts by stimulating the non-pacing arm of the heart. A pacemaker competition occurred when the post-stimulatory frequency of the newly active pacemaker was only slightly greater than the frequency of the previously active pacemaker. When 10 sec. Figure 12. The effect of electrically driving an isolated heart which had only one active pacemaker. This continuous record is a continuation of Figure 11. The intact pace- maker showed periods of activity which were not changed by stimulating the heart from the contralateral end. Note that the quiescent periods fall in the middle and ends of the figure except in the last trace. The intracardiac blood volume was increased during the last trace, abolishing quiescent periods. The ink writer pen was changed at (c). Stimulation is indicated by the hash marks. the post-stimulatory frequency of the newly active pacemaker was lower, an abor- tive pacemaker competition ensued. These results show that an active pacemaker may not be driven (cf. Fig. 12). To test the oscillation reversal theory (see Discussion), the ends of hearts were stimulated with stimulators set at slightly different frequencies. The durations of the reversal-periods and competition reversals were determined by the fre- quencies and the difference in the frequencies of the two stimulators (such as and , and , or and ). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Lillie, Frank Rattra
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectb, booksubjectzoology
