Showing papers by "Ichiji Tasaki published in 1948"

Action currents of single nerve fibers as modified by temperature changes.

Abstract: IN 1931 Gasser (1) carried out a very careful study on the effect of temperature changes upon the action potential of nerve. As Gasser himself states in his paper, comparison of the action potential forms at two different temperatures is subject to considerable possible error. This is mainly due to the different degree of temporal dispersion of the action potentials from different nerve fibers in a nerve trunk at different temperatures but this source of error can undoubtedly be obviated by the use of single fiber preparations for the experiments. The method of “bridge-insulator,” which we have adopted in the present study, seems to eliminate some of the possible sources of error in the ordinary technique of recording the action potential from a single nerve fiber using a slender nerve trunk. With the ordinary technique, the magnitude of the observed action potential is determined primarily by the resistance of the portion of the nerve between the two lead-off electrodes, and it may change from time to time as the fluid around the nerve vaporizes gradually. With a bridge-insulator, the potential is, on the contrary, essentially controlled by the shunting resistance connected between the lead-off electrodes. In the ordinary technique the observed action potential gives information on the activities of several nodes of Ranvier under the active electrode, while in the bridge-insulator method the node in the direct neighborhood of the bridge plays a predominant role in the production of the current observed. It is the purpose of the present investigation to reexamine, with isolated single nerve fibers of the toad, Gasser’s previous observations on the effects of temperature changes upon nerve activity. We are concerned in this paper with the changes in (i) the conduction time, (ii) the spike height, (iii) the spike duration and (iv) the strength-latency relation.

Response of single Ranvier nodes to electrical stimuli.

Abstract: A VERTEBRATE motor nerve fiber is thickly covered with a layer of myelin sheath except at narrow gaps called nodes of Ranvier. As the myelin sheath is shown to be composed of an electric insulator, investigation of the physiological properties of these nodes seems to disclose the nature of the plasma membrane of an infinitesimal dimension and consequently to enable us better to understand the activity of the surface layer of a cell in general. The present investigation is undertaken to secure a series of oscillograms which seemed to us to indicate the basic properties of the plasma membrane at the nodes. The temporal configuration of the electric responses and the latencies of the responses to rectangular current pulses are our main concern in this paper.

Modification of the electric response of a single ranvier node by narcosis, refractoriness and polarization

Abstract: THE PRESENT investigation is undertaken to show how the physiological properties of the plasma membrane at the node of Ranvier is modified by narcosis, the relatively refractory period and electrotonus. We have already dealt with this problem in previous papers (5, 6), and the present study confirms and expands the previous results.