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自己冲动的一个周期。

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发了一个除极，这个心房被称为房性异位起搏点。

So the sinus node waits the same interval but fires based on the ectopic beat.

接下来窦房结又等待了同样的间隔时间，该时间内传导的冲动是基于异位心搏发出的。

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

这些快速渗漏的位于窦房结，或 SA 结，位于右心房上方。

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。

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收缩。

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

P波代表窦房结起的心房去极化。

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。

The gene caused the creation of an exact copy of the sino-atrial node in the heart's upper right chamber.

该基因导致心脏右上腔室中窦房结的精确副本的产生。

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，就重置了所有更慢的，这就是工作的原理。

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。

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.

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

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除极，导致窦房结跳过一个心动周期。

When the atria are full of blood, the SA node fires, electrical signals spread throughout the atria and cause them to depolarize.

心房充盈时，窦房结立即发出冲动，电信号会传遍整个心房并使其去极化。

Heart blocks are classified by location where the blockage occurs: - SA nodal block, or SA block – blockage within the SA node.

-窦房结结阻滞，或窦房阻滞--窦房结内的阻滞。

In this case, after being depolarized, the sinus node waits its 1 second, and then sends another signal and again we carry on as normal.

在这种情况下，窦房结在除极之后等待了1秒，然后发放另一个信号，心搏得以重新正常进行。

In fact, if something goes wrong with this node, a person might need to have an artificial pacemaker implanted to keep their heart's steady beat.

事实上，如果窦房结出了问题，个体可能需要植入人工心脏起搏器来保持心脏的稳定跳动。

Now, if we measure out the interval between each SA node fire, we see that it should have fired here, but it doesn't because it was depolarized by the ectopic focus.

这时，如果我测量每一个窦房结冲动的间隔，我可以看到本应在此处发放，但并没有，因为被异位起搏点除极化了。

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.

如果我稍稍简化一下心脏，正常时，窦房结发放一次电信号，传遍心壁，且上腔室（心房）也收缩。