Propagation speed in myelinated nerve. II. Theoretical dependence on external Na and on temperature.

The Hodgkin-Huxley (H.H.) equations modified by Dodge for Rana pipiens myelinated nerve have been solved to determine how well the theory predicts the effects of changes of temperature and [Na(+)](0) on propagation. Conduction speed theta was found to have an approximately exponential dependence on temperature as was found experimentally, but the theoretical temperature coefficient (Q(10)) was low; 1.5 compared with the experimental finding of 2.95. theta was found to be a linear function of log ([Na(+)](0)) in contrast to the experimental finding of a square root dependence on [Na(+)](0). theta is 50% greater at one-fourth normal [Na(+)](0) than the theory predicts. The difference between the theoretical theta([Na(+)](0)) and the experimental theta([Na(+)](0)) is probably due to an imprecisely known variation of parameters and not to a fundamental inadequacy of the theory.