So, if we simplify this heart a little bit, normally, the sinoatrial node or SA node sends an electrical signal that propagates out through the walls of the heart and contracts both upper chambers.

果我们稍稍简化一下心脏，正常时，窦结发放一次电信号，传遍心壁，且上腔室（心）也收缩。

And those fast, leaky cells are found in the sinoatrial node, or the SA node, up in the right atria.

这些快速渗漏的细胞位于窦结，或 SA 结，位于右心上方。

The starting point of the intrinsic conduction system is the sinoatrial node, or SA node.

在传导系统的起点是窦结。

In a healthy heart, the sinoatrial node or SA node initiates all electrical impulses in the atria.

在健康的心脏，窦结（SA结）产生心的所有电脉冲。