  Noisy saltatory spike propagation along myelinated axons is studied within a
stochastic Hodgkin-Huxley model. The intrinsic noise (whose strength is inverse
proportional to the nodal membrane size) arising from fluctuations of the
number of open ion channels influences the dynamics of the membrane potential
in a node of Ranvier where the sodium ion channels are predominantly localized.
The nodes of Ranvier are linearly coupled. As the measure for the signal
propagation reliability we focus on the ratio between the number of initiated
spikes and the transmitted spikes. This work supplements our earlier study [A.
Ochab-Marcinek, G. Schmid, I. Goychuk and P. H\"anggi, Phys. Rev E 79, 011904
(2009)] towards stronger channel noise intensity and supra-threshold coupling.
For strong supra-threshold coupling the transmission reliability decreases with
increasing channel noise level until the causal relationship is completely lost
and a breakdown of the spike propagation due to the intrinsic noise is
observed.
