Normally the sinoatrial node generates regular electrical pulses that spread across the Chambers of the heart, causing the cells to contract in synchrony.

正常情况下，窦房结产生规律的电脉冲，传入各心房，再带动细胞同步收缩。

youdao

When the heart beats, an electrical signal passes from the top of the heart, near the atria (upper chambers), down through the ventricles (lower chambers), and the chambers contract in that order.

当心脏跳动时，一个电子信号就会从心脏的顶部传到一个心腔（位于上部），然后是位于下部的心腔，当它收缩时，也是按照这样的顺序。

youdao

Yet there is an unwritten contract at its heart: that the winners shall use some of their wealth to compensate the losers.

然而，它的核心却是一份不成文的契约：成功者要用他们的部分财富来给那些失意者以一定的补偿。

youdao

Performance expectations are the heart of the contract between management, the board, and investors.

FORBES: Budget, or Fudge-It?

The minister said that at the heart of the new contract would be a requirement to engage with the local community to help shape and influence the future of cross Forth transport.

BBC: New Forth bridge plans move ahead at Scottish parliament

Yet there is an unwritten contract at its heart: that the winners shall use some of their wealth to compensate the losers.

ECONOMIST: How to spend money and influence people