These mechanical devices that show the relative placement and movement of the planets and moons are sometimes called orreries.

VOA: special.2010.09.29

The balance of sodium movement relative to potassium movement changes because there's this resting movement of all these molecules anyway, but that balance changes dramatically when these ion - when these gated ion channels open.

钠钾各自运动始终保持动态的平衡,因为尽管在静息状态,所有这些离子也在运动,但是平衡的剧烈变化,只发生在这些门控离子通道打开的时侯

耶鲁公开课 - 生物医学工程探索课程节选