So, cardiac cycle, I've written about the phases, intrinsic regulation.

关于心动周期，我写过关于阶段和内在调节的文章。

For example, ventricular bigeminy is when a premature ventricular contraction consistently comes after each normal cardiac cycle.

比如，室性二联律就是室性期前收缩在每个正常心动周期之后持续发生。

Ventricular trigeminy, on the other hand, is when one consistently comes after every two normal cardiac cycles.

而室性三联律，就是一次室性期前收缩持续发生于每两个正常心动周期之后。

A ventricular ectopic focus can fire at different points in the cardiac cycle, which we can look at using the ECG.

室性异位起搏点会在心动周期的不同时间点放电，我们可以用心电图监测到。

Mean arterial pressure is defined as the average arterial blood pressure during a single cardiac cycle.

平均动脉压定义为单个心动周期内的平均动脉血压。

The average arterial blood pressure during a single cardiac cycle is called the mean arterial pressure (MAP).

单个心动周期中的平均动脉血压称为平均动脉压（MAP）。

Each wave or segment of the ECG corresponds to a certain event of the cardiac electrical cycle.

心电图的每一个波或段对应于心脏电周期的某个事件。

The graphs show the heart's OVERALL electrical potential, or voltage, as it changes over time during a cardiac cycle.

这些图形显示了心脏在一个心动周期内随时间变化的总电势或电压。

What I just described is one cardiac cycle, or the sequence of events in a single heartbeat.

我刚刚描述的是一个心动周期，或单次心跳中的一系列事件。

The other phase of the cardiac cycle is called systole.

心脏周期的另一个阶段称为收缩期。

This diastole-systole cardiac cycle (relaxation-filling, then contraction-pumping) lasts about 0.9 second and occurs between 70 and 80 times per minute.

这就是说，心室泵血入动脉通常每分钟70－80次。

When a premature atrial contraction consistently comes after each normal cardiac cycle, it's called atrial bigeminy and when one consistently comes after every two normal cardiac cycles, it's called atrial trigeminy.

当一个房性期前收缩总是紧接着每一个正常心动周期而来时，它被称为二联律；当一个房性期前收缩总是紧接着每两个正常心动周期而来时，它被称为三联律。

Since the average heart beats about 75 beats per minute, the length of each cardiac cycle is less than one second.

由于平均心跳每分钟约75次，因此每个心动周期的长度小于一秒。

Let's look at how pressure rises and falls in the heart as it moves through the different phases of the cardiac cycle.

我们看一下压力在心动周期的不同阶段中如何上升和下降。

This pressure varies over the course of the cardiac cycle, increasing when blood is ejected from the heart(during systole), and decreasing as the heart relaxes(during diastole).

因血管内压力变化与心脏状况、动脉以及其它因素有关，测量血压并对其认真解读能指导护理和帮助评估一个人的健康状况。

At this point, the ventricles are under very high pressure, and now we move into the next phase of the cardiac cycle, called systole.

此时，心室处于非常高的压力下，现在我们进入心动周期的下一个阶段，称为收缩期。

Murmurs are diagnosed based on the time they occur in the cardiac cycle, their changes in intensity over time, and the auscultation site where they are best heard.

杂音的诊断是基于杂音发生在心动周期的不同时期，强度随着时间的变化，以及最佳听诊部位。

This explains what happens during a cardiac cycle, but what it doesn't tell us is how the atria and ventricles know when it's time to contract.

这解释了在一个心动周期内发生的事情，但它没有告诉我们心房和心室是如何知道何时该收缩的。

We remember that a cardiac cycle has two phases: diastole, which is the phase where the heart is filling with blood but not pumping, and systole, which is the phase when the ventricles contract and pump blood.

我们记得，心动周期有两个阶段：心脏舒张期，即心脏充满血液但没有泵血的阶段；心脏收缩期，即心室收缩和泵血的阶段。