First, falling asleep is the beginning of sleep, and the feeling of drowsiness belongs to this stage. At this time, brain waves began to change, the frequency gradually slowed down and the amplitude gradually decreased.
Second, the formal sleep begins during the shallow sleep period, which belongs to the shallow sleep stage. At this time, the brain waves are gradually irregular, and the frequency and amplitude are large and small. Occasionally, there will be high-frequency and large-amplitude brain waves of "sleep spindle" and low-frequency and large-amplitude brain waves of "K junction".
Third, deep sleep and deep sleep are both deep sleep stages, so it is not easy to be woken up at this time. At this time, the brain wave changes greatly, the frequency is only 1~2 cycles per second, but the amplitude increases greatly, showing a slow curve.
4. During REM, brain waves change rapidly, and there will be high-frequency and low-amplitude brain waves similar to those in awake state, but there will be sawtooth waves with distinctive characteristics. Sleepers usually turn over and wake up easily. Because, at this time, in addition to the changes of brain waves, the subjects' eyes will also have a rapid beating phenomenon.
Extended data:
Reasonable sleep should be 7~9 hours every night, which is the guarantee of sleep quality. Sleeping 7~9 hours every night is the regular sleep time from falling asleep to waking up. After adults fall asleep, the pituitary gland first increases the secretion of growth hormone, promotes cell metabolism, restores physical strength and stores physical strength. This process takes about 80~90 minutes and belongs to the "body sleep" stage.
Studies have proved that people who go to bed early and get up early have less mental stress and higher mental health level than those who often stay up late. The scientific time to fall asleep is 22:00-22:30, and you will fall into deep sleep after half an hour or an hour, and the best time for the human body to naturally fall into deep sleep is 12 from midnight to 3 am.
Baidu encyclopedia-sleep cycle