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My question is very simple: why is it sufficient for a very few ions (such as 1 in 100000 K+) to move across the membrane to generate a remarkable variation in the membrane potential (like a change of 100mV) ??

I took the examples from my university textbook, which, though, doesn't explain the reason behind this statement. Is it because during this event the permeability changes so dramatically that the number of ions doesn't have to be so big?

Can someone help me? Thank you!

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  • $\begingroup$ See this answer: essentially, it's because when you are talking about the charge from moving ions across a membrane, 100mV is actually not that remarkable, from an electrical standpoint. You only need 1 microcoulomb of charge per sq cm of membrane to change the membrane potential by 1 VOLT and a cell has a lot less membrane than that. $\endgroup$
    – Bryan Krause ♦
    Commented Mar 26, 2017 at 16:52

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