Question

If the threshold is the membrane potential AT WHICH sufficient number of Na+-voltage gated channels OPEN such that the membrane permability of sodium is greater than potassium, then HOW does the membrane potential get to the threshold in the first place?

Answer 1

Or you can take a stab at question #2:
- why is it that axons with thin diameters need to have more ion channels, while those that are fatter (wider diameters) can have relatively fewer, and yet still sustain AP propagation down the axon?

@blues

Answer 2

@Hcgturtle