They essentially turn the whole SA node into your natural pacemaker.

它们本质上将整个 SA 节点变成你的自然起搏器。

This means that the SA node essentially skips one cycle of sending its own signal.

这意味着窦房结跳过了发放它自己冲动的一个周期。

Normally, an electrical signal starts at the sinoatrial or SA node in the right atrium.

通常，电冲动从位于右心房的窦房结开始。

If an atrial cell outside of the SA node initiates a depolarization, it's called an atrial ectopic focus.

如果一个窦房结以外的心房细胞引发了一个除极，这个心房细胞被称为房性异位起搏点。

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房结，或 SA 结，位于右心房上方。

One important effect of the premature depolarization is that the ectopic focus will depolarize the cells of the SA node, causing the SA node to skip a cycle.

过早除极的一个重要影响就是异位起搏点将会使窦房结细胞除极，导致窦房结跳过一个心动周期。

So let's say the SA node is firing along as usual, but all the sudden an ectopic focus fires one off early.

比方说窦房结和往常一样发放冲动，但是一个异位起搏点提前发放冲动阻断了这些冲动的传播。

Notice that each time the SA node fires, it resets all the slower ones, and this is exactly how it works.

注意每次窦房结放电，它就重置了所有更慢的细胞，这就是它工作的原理。

If, for example, the SA node stopped altogether, then the AV node would take over at it's slightly slower pace.

比如说，如果窦房结一起停止工作，那么房室结就会接任，以一种稍慢的速率。

Let's use this bar to visualize the SA node's depolarization rate, which is the fastest, and then each one below is slightly slower.

让我们用这个进度条来表示窦房结的去极化速率，它是最快的，然后下面的每一条都稍慢一些。

And everything I just described to you — from when the SA node fires to when the last of the ventricular cells contract — takes about 220 milliseconds.

我刚才向你们描述的一切——从 SA 节点触发到最后一个心室细胞收缩——大约需要 220 毫秒。

Electrical impulses from the SA node spread throughout both atria and stimulate them to contract.

窦房结发出的电脉冲扩散到整个心房并刺激它们收缩。

We previously learned that the SA node initiates the electrical impulse that travels through the heart.

我们之前了解到，SA结会引发穿过心脏的电脉冲。

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

内在传导系统的起点是窦房结。

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

在健康的心脏内，窦房结（SA结）产生心房内的所有电脉冲。

P wave represents depolarization of the atria initiated by the SA node.

P波代表窦房结引起的心房去极化。

The cells of the SA node can depolarize on their own without any external influence.

SA结细胞可以自行去极化而不受外界影响。

The SA node is very important, and it's often referred to as the pacemaker of your heart.

SA结非常重要，它通常被称为心脏起搏器。

Sinus rhythm is the normal rhythm of the heart set by its natural pacemaker in the SA node.

窦性心律是SA结中自然起搏器设定的心脏正常节律。

In the heart, we call this out-of-sync behavior fibrillation, and it can be caused by all sorts of problems, especially ones that affect the pacemaker cells in the SA node.

在心脏，我们称之为不同步行为颤动，它可以由各种问题引起，尤其是那些影响 SA 节点中起搏细胞的问题。