The latent period of anode break excitation in myelinated and giant axons

The time lapse (latent period) between a hyperpolarizing pulse and anodic break response was investigated in single myelinated (frog) and giant axons (squid). The latent period was found to first decrease when the stimulating current intensity was gradually increased beyond threshold. However, for higher stimulus intensities the latent period increased and became a direct function of stimulus intensity. These findings were shown to be consistent with the Hodgkin-Huxley axon model. The initial decrease in latency was shown to be related to the changes in potassium current. The following increase in latency was due to the passive cable properties of the fibres. The increased tendency of sensory and other fibers to fire repetitively is analysed in view of the above findings.