Model investigation of the mechanisms of conductance along excitable fibres in the recovery cycle.

The method of mathematical modelling is used to study the excitability changes of the membrane of the fibres (frog muscle and myelinated nerve fibres at 20 degrees C) and the parameters of the action potentials during the first 30 ms of the recovery cycle. With increasing interpulse interval, unlike the myelinated fibres for the muscle fibres, the subnormality of membrane excitability is followed by supernormality. In the recovery cycle, for the two types of the membranes, the shape (polarity, sequence and number of phases) of the action potentials are unchanged. The time and amplitude parameters of the potentials are only known to vary. With increasing interpulse interval, the amplitudes of the second potentials increase and their durations are shortened attaining the values of the corresponding quantities of the initial action potentials. Supernormality in the velocity recovery cycle is not obtained. The membrane properties for the myelinated nerve fibres are recovered 20 ms after application of the initial pulse. For the muscle fibres, the membrane properties are recovered after 30 ms, but the supernormality of the excitability is still preserved.