Abstract
It had been well known that the smaller height and shorter duration of the spike occurred during the relative refractory period than those in the normal state of the nerve. But the reason is still not elucidated at all. In this paper the results of investigation of these phenomena were reported. Materials used in the experiments were the sciatic nerve of the bullfrog and the electric nerve model (ENM) composed of electric elements and devised by Matumoto et al. This model is an equivalent circuit of the nerve fiber representing almost all phenomena already known on the nerve fiber in similar state as in it.
Therefore, the author assumed that the mechanism of these phenomena could be substituded with that elucidated on the artificially composed ENM for the same phenomenon. The following were the obtained results.
Reduced excitability due to the decreased charge of the capacity of the excitable membrane was the origin of the higher threshold in the relative refractory period, while the smaller height and shorter duration of the spike resulted from the weaker intensity of the discharge current of the capacity of the excitable membrane. Both phenomena appeared by the same origin in general case, but in details the mechanism was different in these two, and they could be separated in the special case.
