Blood is only expelled from the heart when it contracts.

心脏收缩时，血液才从心脏射出。

Right after the S1 sound, the aortic and pulmonic valve open up allowing blood to get pushed out to the body and this period of time is called systole.

在S1之后，主动脉瓣和肺动脉瓣打开，分别使得血液流入身体各组织以及肺部，这段时期叫做心脏收缩期。

It's highest during systole, when the heart contracts to force blood through the arteries.

血压在心脏收缩的时候是最高的。当心脏收缩迫使血液通过动脉。

And they do that because your ventricles contract to build up pressure and pump blood out of the heart. This high pressure caused by ventricular contraction is called systole.

它们这样做是因为你的心室收缩以增加压力并将血液泵出心脏。这种由心室收缩引起的高压为心脏收缩。

Now in addition to systolic heart failure, you've also got diastolic heart failure, which is where the heart's squeezing hard enough but not filling quite enough.

除收缩性心衰外，还有舒张性心力衰竭，指的是心脏收缩功正常，但是在舒张期充盈受损。

It would squeeze the capsule tightly as the heart contracted and still keep a firm grip on it when the heart was relaxed.

它可以随着心脏的收缩轻微挤压胶囊，且在心脏放松时，抓住。

Cotton was the heartbeat of the section, the planting and the picking were the diastole and systole of the red earth.

棉花便是本地区的脉搏，植棉和摘棉便是这红土心脏的舒张和收缩。

The heart contracts and expands in a non-stop rhythm to push our blood around a system of arteries and veins.

心脏不间断地收缩和舒张，推动血液在动脉和静脉系统流动。

That is reassuring. But what about the other bad beats, the premature contractions in the heart's lower chambers?

这就让人放心了。那其他有害心跳，发生在心脏下腔的期前收缩(室性期前收缩)呢?

The second heart sound, " dub" , is called S2, and the noise comes from the aortic and pulmonic valves snapping shut to prevent blood from flowing backwards after it leaves the ventricles, effectively ending systole.

第二心音“dub”，它被为S2，声音来自主动脉瓣和肺动脉瓣关闭，以防止血液在离开心室后反流，有效地结束心脏收缩。

Alright, so also the location of the ectopic focus in the atria determines how the heart contracts and therefore what the ECG looks like.

并且心房异位起搏点的位置决定了心脏如何收缩以及因此产生的心电图形状。

That being said, that contraction pumps the blood out the pulmonary valve, which just like the tricuspid valve has three cusps and also prevents blood from going backward.

就是说，心脏收缩将血液泵出肺动脉瓣；与三尖瓣一样，肺动脉瓣有三个尖瓣，可防止血液倒流。

And this can quickly lead to cardiogenic shock, since the heart doesn't even have time to fill with blood before each contraction.

这很快会导致心源性休克的发生，因为心脏在收缩之前还来不及充盈血液。

This can happen in two ways, either the heart's ventricles can't pump blood hard enough during systole, called systolic heart failure, or not enough blood fills the ventricles during diastole, called diastolic heart failure.

这可以两种方式发生：一种是心室在心脏收缩期不足够有力地泵出血液，即收缩性心力衰竭；另一种是在心脏舒张期心室充盈不足，即舒张性心力衰竭。

When the heart contracts, that papillary muscle keeps the chordae tendineae taut; and both of these help to prevent regurgitation of blood back into the atrium, allowing it to only flow out the next valve.

当心脏收缩时，乳头肌使腱索绷；两者有助于防止血液反流到心房，使血液只从下一个瓣膜流出。

Also, though, the timing of the PAC will also determine how the heart contracts and therefore what the ECG looks like.

此外，房性期前收缩的时机决定了心脏如何收缩以及因此产生的心电图形状。

The nerves that control unconscious processes such as the heartbeat can sense distress and trigger a maladaptive fight-or-flight response that triggers blood vessels to constrict, the heart to gallop and blood pressure to rise, resulting in damage.

控制心跳等无意识过程的神经可以感知痛苦并引发适应不良的战斗或逃跑反应，从而触发血管收缩，心脏奔驰和血压升高，从而导致损伤。

And so there is your heart is not strong enough in a single contraction, your left ventricle, your heart that's ejecting that blood is not strong enough to push the blood through 63,000 miles of vessel.

因此，你的心脏在一次收缩中力量不足，即你的左心室， 负责将血液泵出的心脏， 其力量不足以推动血液通过长达63,000英里的血管网络。

And what we found was that stimuli that occurred during heart's contraction were perceived to last shorter than stimuli that occurred between the beats, when the heart was relaxed.

我们发现，心脏收缩期间发生的刺激持续时间比心脏放松时两次心跳之间发生的刺激持续时间短。

It would squeeze the capsule tightly as the heart contracted and still keep a firm grip on it when the heart was relaxed To test this idea.

它会在心脏收缩时挤压胶囊，并在心脏放松时仍然牢牢抓住它。为了测试这个想法。