Abstract
To elucidate the electrophysological nature of the skeletal muscle in refractory state, the present research was undertaken. Materials were exclusively hybernating Bufo vulgaris, of which sartorius muscle was used in the experiments. Dual stimuli of various interval were applied on the pubic end of the muscle and evoked action potentials were led from two parts, one of which was 1.8 cm distant from the cathode of stimulating electrodes and the other was 2.8 cm distal from the same electrode. The distance between the two leading parts was 1 cm. The action potentials led from the two parts were recorded simultaneously by the two beams oscilloscope. Both intensities of the succeeding two stimuli were supermaximal in the physiological meaning.
In this way the excitability cycle of the skeletal muscle were pursued, utilizing the strength of the action pontentials as the indicator of excitability.
The absolute refractory period was lengthened as the leading part became far from the stimulating point. Action potential in refractory period was always stronger in proximal part than in distal part. It was obvious that the conduction of action patential along the muscle fiber in refractory period was decremental. The velocity of the action potential showed also negative acceleration
Subnormal weak action potential evoked at the stimulating part in early relative refractory period proceeded for short distance and vanished there. This is the reason of that the absolute refractory period in distal part of the one and same muscle fiber is longer than in proximat part.
So called“response-recovery curve” (a graphic representation of the relation between the strength of action potential and the interval of dual stimuli) obtained from the distant part from stimulating electrode, retarded than that from the proximate part.
Recovery curve of the conduction time was also pursued. Recovery of the conduction time of the proximate part was quicker than that of the distant part.
In these ways, the recovery processes are different according to the different parts of the one and same excitable system.
So called recovery curve can not be the representation of the whole recovery process of one excitable system. It shows only the excitable cycle of any one point of the system.
To represent the whole recovery process of that system, three dimensional curved surface must be utilized, in which X-axis shows the interval of the dual stimuli, Y-axis the conduction time and Z-axis the intensity of action potential.
The present auther propose to name such surface as recovery surface.
From above mentioned facts, it could be concluded that the skeletal muscle which showed isobolic behavior in the meaning of Verworn in normal state, shifts to heterobolic system in relative refractory period.
