which conducts electricity,

所以是导电体
that you can measure those changes in electrical potential

因此你可以通过安放于体表的电极
happening in cells in the heart by having electrodes

检测到心脏细胞中发生的
just on the surface of your skin.

那些电位变化
The EKG arises from all of these action potentials that are happening

心电图就是源于心脏中成千上万的细胞
within all of the thousands of cells within your heart.

所产生的所有这些动作电位的总和
This diagram is a little easier to understand.

这副图表更容理解些
It had more words than I liked so I blocked some of them out.

文字太多所以我剔除了一些
The other one are things that we've already talked about before,

剩下的是我们之前已经讨论过的
the SA node is now familiar to you,

窦房结现在大家都熟悉了
the sinoatrial node,

窦房结
the AV node,

房室结