So, for example, if we look at sodium channels, and sodium channels are some of the particularly prevalent ones when we're talking about neurons, if you think about the cell membrane, and this little green cartoon is me trying to show a sodium channel here, and in this case, you can see that it's closed, such that no ions are getting through.

比如，让我们来看一下钠离子通道，钠离子通道是我们会经常遇到的几个之一,在讨论神经元的时候，如果大家想想细胞膜，而这个绿色的小示意图就是我用来表示,钠离子通道的，在这种情况下，大家可以看到它是关闭的，因此没有离子可以通过。

麻省理工公开课 - 化学原理课程节选