NREM Stage 2, accounting for 45-55% of total sleep, is deeper than the first one. It is more difficult to be awaken from than from the NREM 1. This stage is characterized by [[Wikipedia:K-complex|K-complexes]] and [[Wikipedia:sleep spindles|sleep spindles]], which are abrupt interruptions in alpha waves activity. This stage of sleep also plays a role in maintaining wakefulness over long periods.
NREM第二阶段是比第一阶段更深的睡眠，占总睡眠的45至55%。与NREM1相比，在NREM2中更难被唤醒。这个阶段的特征是K-复合波和睡眠梭状波，即Alpha波活动的突然中断。这阶段的睡眠也负责维持长时间的清醒状态。
