来自《耶鲁大学开放课程：生物医学工程探索 第15集 第15集》

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  Every cell in your body at a given time is going to
  机体内的每个细胞在特定的时间
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  have lots of potassium channels that are open
  都会有很多的钾离子通道开放
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  and lots of sodium channels that are open.
  也会有很多的钠离子通道开放
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  They're just some that are open all the time.
  还有一些是一直处于开放状态的
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  Because of that
  正因如此
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  there's a continual leakage of potassium out of the cell
  钾离子可以持续性的漏出胞外
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  and a continual leakage of sodium into the cell.
  钠离子持续性的漏入胞内
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  Well,if ions are moving across the cell membrane,
  如果离子要跨膜移动
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  ions are charged molecules,
  离子是带电的分子基团
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  and that movement is a current.
  这样的移动就形成了电流
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  You usually think of currents as movements of electrons
  通常你会认为电子的移动才是电流
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  but movements of ions,
  但离子移动