In the description of the electrical circuit that models a piece of membrane
in Rall's Scholarpedia article on Ralls model, I read:
"[...] this conductance [$G_e$] is zero under resting conditions, but is turned on by an excitatory synaptic input. [...] this conductance is [$G_i$] zero under resting conditions, but is turned on by inhibitory synaptic input."
Does this mean, Rall is assuming voltage-dependent ion channels? Or why does he stress, that the conductances can (or even must) be turned on and off?
From an electrical point of you, I would guess, that the three resistancy-battery pairs can be replaced by one such pair that would not be voltage-dependent, and maybe even the battery is not needed, as in cable theory:
Or would Rall's model not work anymore, then? This doesn't get clear to me, and would not have been stressed by the author. (Later in his article, Rall doesn't mention $G_r$, $G_e$, $G_i$ anymore, but talks only about membrane resistance $r_m$.)