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I have a question about the resistance of neuron membrane. According to the cable equation:
rm = R/(2pia)
cm = C2pia
where a is the axon radius, when I change 'a' in the model, will rm and cm change automatically with 'a' by the above equation in Neuron?

NEURON computes the coefficients in the discretized cable equation from the physical dimensions and biophysical properties of each section. If any diameter, length, discretization parameter nseg, or biophysical parameter (channel density or whatever) is changed, NEURON automatically revises the contents of its internal data structures during initialization.