In the heart, action potential is moving from one heart muscle cell to another over the surfaceof the heart.
在心脏中，动作电位是在心脏表面从一个心肌细胞向另一个心肌细胞传递。
2
In the laboratory, when the seal dives below the surfaceof the water and stops breathing, its heart beats more slowly, requiring less oxygen, and its arteries become constricted.
在实验室里，当海豹潜入到水面以下并停止呼吸时，它的心脏跳动得更慢，需要的氧气更少，动脉也会收缩。
3
He was breathing hard and thenhis heart sank when he realized just how long of a surface swim hestill had in front of him.