Proteins known as CLK, or clock, accumulate in the SCN throughout the day.

称为 CLK 或时钟的蛋白质全天都在 SCN 中积累。

Then, clock falls low, so PER concentrations also drop again, allowing CLK to rise, starting the cycle over.

然后，时钟下降，因此 PER 浓度也再次下降，允许 CLK 上升，开始循环。

When enough PER accumulates, it deactivates the gene that makes CLK, eventually making us fall asleep.

当足够的 PER 积累时，它会使产生 CLK 的基因失活，最终使我们入睡。