When you sleep you get the following stages.

睡眠有以下几个阶段。

耶鲁公开课 - 心理学导论课程节选

When you're really tired sleep is what you want to do like when you're really hungry you want to eat.

你累了，就会想睡觉,正如你饿了想吃东西一样。

耶鲁公开课 - 心理学导论课程节选

When you're in dreamless sleep, you're not imagining or experiencing anything.

当在无梦的睡眠中时，你没有想象或者体验任何事。

耶鲁公开课 - 死亡课程节选

First,we'll put you to sleep when we do all this procedure.

首先会让你进入睡眠状态。

耶鲁公开课 - 死亡课程节选