期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1970
卷号：65
期号：4
页码：884-891
DOI：10.1073/pnas.65.4.884
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Evidence is presented to show that for a squid axon membrane the potential response, V, is a smoothly continuous function of a stimulating current, I. This makes it unlikely that an all-or-none or sharp transition phenomenon is a major factor in the processes by which ions cross the normal squid axon membrane and, probably, other excitable membranes. Spatially uniform V and I were first produced in the squid axon with internal and external electrode arrangements and later by isolating a short length of axon between external pools of sucrose. Under these simplified conditions, direct experiments and calculations based on the Hodgkin-Huxley empirical conductances agree in showing that the maximum response, R, is a continuous, single-valued function of the effect of the stimulus, S. The maximum value of {Delta}R/{Delta}S decreased steadily as the temperatures were increased from 25{degrees} to 38{degrees}C. Uncontrolled fluctuations prevented direct observations of {Delta}R/{Delta}S below 15{degrees}C where calculations showed that it rose rapidly as the temperature decreased. Since the conductances are experimental parameters and since {Delta}R/{Delta}S as calculated from them remained finite and continuous event at 6.3{degrees}C, this is experimental evidence against an all-or-none threshold excitation. However there is an all-or-none threshold for the initiation and propagation of an impulse along an axon where V and I are functions of both time and distance.
