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Sharpness of Spike Initiation in Neurons Explained by Compartmentalization

Figure 1

Sharpness of spike initiation with distal initiation (Na channels clustered at a single point).

A, Proportion of open Na channels as a function of the voltage of an isopotential neuron. B, Current-voltage relationship in the isopotential neuron with Na and leak channels. C, Current-voltage relationship in a ball-and-stick model, with Na channels at the soma (dark blue), and at 20 µm (green), 40 µm (red) and 100 µm (light blue) away from the soma. D, Proportion of open Na channels as a function of somatic voltage of the ball-and-stick model (color code as in C). E, Voltage across the axon as the soma is depolarized by steps of 3 mV (4 values from −64 mV to −55 mV), with Na channels at 40 µm from the soma. F, Voltage at the initiation site as a function of somatic voltage, showing the loss of voltage control around −55 mV.

Figure 1