Yea,those channels. They're complicated and x ray crystallography only broadly supports a thesis they are little holes. There's all kinds of weirdness going on, opening and closing by twisting under voltage and other stimuli. If you think it's a little pipe or even like a stomata (which is a macrocellular structure in plants which have cell walls in real sense) you've been led down the metaphor too far. Or, so I am told. I'm not a cell biologist.