Sleep is a spontaneous and reversible resting state that occurs periodically in higher vertebrates and manifests itself as a decrease in the body's responsiveness to external stimuli and a temporary interruption of consciousness. About 1/3 of a person's life is spent in sleep. When people are in the state of sleep, it can make people's brain and body get rest, rest and recovery, and the right amount of sleep can help people's daily work and study. Scientific improvement of sleep quality is the guarantee for people's normal work and study life.

　　Basic Information

　　Chinese name :sleep, sleep Chinese sleep, sleep Name :sleep, sleep

　　Foreign name :sleep

　　Reason :To organize memory

　　Category :Biological Behavior

　　Cause of sleep

　　Sleep is a state in which sensory and motor activities are temporarily halted due to the body's internal needs and can be awakened immediately by appropriate stimulation. After recognizing the electrical activity of the brain, it is believed that sleep is caused by the functional activity of the brain, which leads to low physiological activity of the animal, and can be brought to a state of full wakefulness by giving appropriate stimulation.

　　Sleep is an active process, sleep is the rest necessary to restore energy, there are specialized centers to manage sleep and wakefulness, sleep when the human brain is just a change in the way of work, so that the energy is stored, conducive to the recovery of mental and physical strength; and proper sleep is the best rest, both to maintain the health and physical strength of the foundation, but also to achieve a high degree of productivity to ensure. Acceptance of processing internal and external stimuli and respond to the higher degree of excitability of the nerve cells by preventing the stimulus linkage that has not been deeply processed interfere with each other, which is manifested in the relief of fatigue. In contrast, poor quality sleep is a phenomenon of insufficient shielding or insufficient sleep time to adequately digest stimulus associations. Somnolence, on the other hand, is pathologically too much and too long shielding. These are manifestations of inadequate neural control. During sleep the state of the body is restored due to diminished active activity.

　　The most important function of sleep is reflected in the brain, and the sleeping state coheres and organizes the scattered fragments of memory in the brain together through dreaming. The brain is organized by dreaming.

　　Physiological changes

　　Sleep tends to be an unconscious and pleasant state, usually occurring while lying in bed and during the night when we allow ourselves to rest. In contrast to the waking state, during sleep a person's contact with their surroundings ceases, their conscious awareness disappears, and they no longer have control over what they say or do. People in the sleep state have relaxed muscles, weakened nerve reflexes, a drop in body temperature, a slowed heartbeat, a mild drop in blood pressure, a slower metabolic rate, and a noticeably weaker peristalsis of the gastrointestinal tract. At this time it looks like sleeping people are still, passive, actually not, if a person sleeps in his electroencephalogram, we will find that people in the sleep of the brain cells issued by the electrical impulses is not weaker than the waking time. This proves that the brain is not resting. Just like a beehive at night, it may appear that the bees have returned to the hive and are resting, but in reality all the bees are busy all night long making honey.

　　Normal adults fall asleep, the first into the slow wave phase, usually in the order of 1 ~ 2 ~ 3 ~ 4 ~ 3 ~ 2, etc., lasted 70 to 120 minutes, that is, the transition to anisocoria sleep, about 5 to 15 minutes, so that the end of the first phase transition, and then start the slow wave phase, and into the next anisocoria sleep, and so on and so on. Throughout the sleep process, there are generally 4 to 6 transitions, with the slow wave phase duration shortening and dominated by the 2nd phase, while the heterophase duration gradually lengthens. Taking the full duration of sleep as 100%, slow wave sleep accounts for about 80%, while heterophasic sleep accounts for 20%. Arranging the different sleep phases and arousal states according to the time sequence of their appearances, a sleep chart can be drawn, which can visually reflect the dynamic changes of each sleep phase.

　　Sleep pattern

　　Sleep consists of two alternating different phases, one is the slow wave phase, also known as non-REM sleep, and the other is heterophasic sleep, also known as REM sleep, in which rapid eye movements and frequent dreams occur. REM sleep is primarily used to restore physical energy, and non-REM sleep is primarily used to restore brain power.

　　Slow Wave Sleep

　　According to the characteristics of human brain waves, this phase is usually distinguished into 4 different phases, that is, corresponding to the process of sleep from light to deep. Stage 1 presents low-voltage brain waves with a mixture of fast and slow frequencies, while a frequency of 4 to 7 weeks/second predominates, which often occurs at the beginning of sleep and brief awakenings during the night.