As adults we spend or should if we don’t one third of our time in sleep and as children up to half of their time. We all sleep when tired and when have a good sleep, we would feel rested. We therefore know that the sleep function is for restoration of physical tiredness or fatigue. But sleep is not just for restoration of physical fatigue, but for the restoration of the mental or brain fatigue as well. We may think that during the sleep, the body is totally shout down and in rest. But surprisingly the body is quite active in sleep and like a factory, does self-restoration or repair during the hours of sleep. In deep sleep, if we can get any, the physical restoration or repair is done and in REM (Rapid Eye Movement) or dream stage of sleep, the mental or brain restoration or repair is done. More importantly, many hormones such as growth hormone in children are secreted in sleep and mostly in deep sleep.
In this paper, the architecture or different stages of sleep will be explored. Then the sleep-wake cycle that is a major component of our circadian rhythm and our body homeostasis and health balance will be exposed. Then the importance of sleep hygiene and lack of it and the disorders of sleep will be discussed. The treatment for sleep disorders and the most common one, insomnia or sleeping pills will not be discussed, as majority are of Benzodiazepine class of drugs, addictive and more habit forming and perpetuating the insomnia. The purpose of this article among the others on this site is more to understand the pathophysiologic process of every disease, so hopefully soon move towards the prevention. Finally what is a very dilemma and question for many, the world of dream and its interpretations will be explained.
Stages of sleep:
During a night sleep of about 8 hours that is normal for adults, the body or brain goes through about 5 cycles, starting with the stage 1 that is the drowsiness or falling asleep stage lasting only a few minutes. Then the second stage that comprises about %45-50 of a normal adult sleep, that is still light and the person could be aroused by sounds and noises and it is the usual toss and turn stage of sleep. The second stage lasts about 40-45 minutes in each cycle that lasts normally 90 minutes. Then the deep sleep kicks in that is comprised of stages 3 & 4 and most adults do not get it much nowadays, while they need to have it at least %20 of their sleep. These stages of 3 & 4 or deep sleep is for the restoration of physical fatigue and if the person does not get it enough, he or she would not feel rested in the morning.
The next stage of sleep in the cycle is REM (Rapid Eye Movement) sleep that is the dream stage of sleep when the individual enters the world of his or her dreams. This stage that comprises about 20-25% of a night sleep is very active not just for the eyes that moves fast as its term suggests, but the whole body physiology such as heart beat, respiration and else are active even more than in the waking state. After the first cycle of sleep and REM, the brain may not start over from stage 1, unless someone’s sleep is very light and broken and keeps waking up in the middle of the night, or after a nightmare. So in a normal restful sleep, after the first cycle and REM, in the second cycle and thereafter, the brain starts from stage 2 and the rest. If the individual’s sleep is light, he or she may not go much or at all through the deep sleep of stages 3 &4 that is very common in the modern era of sleepless nights. Therefore everybody gets mostly stage 2 and REM sleep even if one does not remember having any dreams. REM sleep due to its high brain and physiological activity, has the vital role of restoration of brain fatigue. That’s why people with many mind preoccupation or worries may have lots of dreams and even nightmares. The following figure shows how the body enters the different stages of sleep from a waking state and the repeated sleep cycles throughout a night sleep:
Now in the following each stage of sleep will be discussed in more detail:
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