Different chemical reactions occur at the battery's positive and negative electrodes.

电池的正极和负极会发生不同的化学反应。

In fact, if there's a depolarization wave that goes straight up, which is perpendicular to the positive and negative electrodes, then there'd be no deflection at all!

事实上，如果有一个除极波是竖直向上的，即完全垂直于正、负电极的话，那么心电图上就不会显示任何波形。