So voltage gated channels and ligand gated channels are actually closed when that membrane is the rest, and they're only open when that membrane is excited by some type of stimulus. Now, when they do open, they're only open for a very short period of time, about a milliseconds or so, and then they're quickly closed off or they're inactivated. And the size of the pore inside these channels is actually very small. And that's why only small inorganic ions can pass across. And finally, these ion channels are usually very specific to the type of ions they allow across that membrane. Now, what about gap junctions?