【alertness音标】 英[əˈlɜːtnəs] 美[əˈlɜːrtnəs]
【单词释义】 alertness是什么意思：
n. [U]警戒，机敏
[单词分级] 商务/生活英语词汇
【单词例句】
◇ That's because when you wake up, your endocrine system begins to release alertness hormones to get you ready for the day. By going back to sleep, you're slowing down this process. Plus, nine minutes doesn't give your body time to get the restorative, deep sleep it needs.
这是因为睡醒后，人体内分泌系统开始分泌清醒激素，唤醒身体。睡回笼觉会减慢这一过程。另外，9分钟的时间根本不够进入让人精神焕发的深度睡眠。