On the capacity current in myelinated nerve fibres

Different equivalent circuits are presented to describe the capacity current, Ic, of potential-clamped Ranvier nodes. The corresponding transfer functions are discussed in examining the influence of the involved parameters on size and time course of Ic. The following results were obtained: i. The duration and the amplitude of Ic increased with increasing membrane capacity. ii. The amplitude of Ic increased with increasing gain or decreasing time constant of the clamp amplifier while its duration was shortened. iii. Similar effects were seen with decreasing resistance in series with the nodal membrane. iv. Qualitatively identical but stronger effects were seen with increasing bandwidth of the current measuring internode. Measurements were carried out under experimental conditions close to the calculated ones. They resembled the calculated curves satisfactorily.