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

The mortgage payment was decided when you took out the mortgage, so that never changes; they than figure out what your mortgage balance is.

每月偿还额是一开始确定的,因此不变,这样就能算出当前的贷款余额

耶鲁公开课 - 金融市场课程节选