The lifetime of a human being develops by cycles. They are gestation, childhood, youth, adulthood, maturity, aged, and death. We observe in nature, as well, the cycle of the 4 weather seasons, moon cycle, tide cycle, night and day cycle, among the most important ones. In every one of these cycles the human being has fit himself in different ways. In certain occasions, the adjustment has been smooth, and in other ones absolutely difficult. The day-night cycle is the one that has suffered a more radical process of adaptation, from a wakeful state, to an unconscious sleep state. This change between a sleep period and a wakeful period is inherent to all mammals, with the exception of the anteater. Sleep is a natural phenomenon, in constant evolution, adaptation and like every phenomenon with these characteristics it has important functions for the lifetime of a person. Some of the sleep stages supplement the wakeful state. For instance, during our sleep, we recover us physically from fatigue we have experienced during the time we were wide awake. Is in that period that our mind adapts again, after a day full of unmeasurable stimulus. A sleep is organized in cycles. During our sleep we experience a different physiological state. It has been noted some of the following changes. Brain waves vary, if you compare with the wakeful state, the muscles enter in a relaxing period, there is a reduction of the body temperature, the eyes move, the respiratory and cardiac rhythm modify, besides some hormonal index alter, among other changes. The sleep is classified in five stages. Four of them are non-REM –of the acronym Rapid Eyes Movement– and its main feature is a circular movement of the eyes, and the fifth one of REM sleep. This division between REM sleep and absence of REM is because during this REM sleep period is when we dream with more frequency. The sleep stages without REM are classified from 1 to 4. Stage 1 its main characteristic is being a transition between waking and sleep. We are more relaxed; sometimes we can feel ourselves lighter and the thoughts and images are more and more diffusive. But at any time when, for example, we hear an unexpected noise, we swiftly recover the wakefulness. As we change from one stage to another, the sleep becomes deeper into dreaming. In stage 4, which is reached in about one hour after we fall asleep, we are totally relaxed and with a lot of insensibility to external stimulus. After a while in this stage 4 the sleep goes back to its initial stages in a descendent order; stage 4, stage 3, stage 2. It is one and a half-hour after it is initiated the sleep period, appears the first REM sleep of the night. When the REM sleep ends, the sleep becomes again deep; stage 2, stage 3, stage 4, so it comes back in a decreasing order to the REM sleep. As long as these cycles happen we stay longer in the REM sleep, it means, more time dreaming and less time in the deeper stages. However, in the last cycles we do not reach the deepest level, stage 4, staying longer in the REM stage. In a normal sleep night we have 4 to 5 REM sleeps, which means we dream four to five times every night, whether we remember it or not. The REM stage is the sleep period where dreams manifest themselves with more frequency. If we are awaken during our REM stage, we will almost certainly remember what we were dreaming. Due to this fact the scientists arrived to the conclusion that, we, all human beings dream. In other sleep stages, it could or couldn’t come images. Some researchers name the REM sleep, the paradoxical sleep. The first REM sleep of the night happens about 90 minutes after we fall asleep. The first dream lasts approximately 3 minutes, the second one approximately 10 minutes and the third one last even longer than the second one. The last REM sleep of the night can last until one hour. The perception we have that dreams are extremely transitory is opposed to reality. It is quite possible during the same REM sleep period to have many dreams, and we only remember some fragments of them. So, when we wake up in the morning, we hardly remember just one fraction of what we really dreamt during the night. Hoewever, the difference between what we dream and what we remember of the dream, due to the biological factors previously described, there is an important connection. The origin of this connection resides in two factors; the content of a dream that one remember is the same of the images that were dreamt, but in a partial and condensed way. The energy that produced the dream is the same that is stored in the memory. In stage 4, which is the one of deepest sleep, it is increased when there is an excess of physical activity, during the wakeful hours. On the other hand, there is an increase of REM sleep, as a consequence of a major intellectual activity. The time we spend dreaming is not the same during lifetime. During the first months when the REM sleep is more frequent, 8 hours, out of 17 hours the baby spends sleeping, are REM sleep. In adults, if we sleep 8 hours, 1/4 of those hours are REM sleep. Elderly people sleep less than young people and, therefore, their REM stages are in declination. The REM sleep is rather more related to a process of psychical reparation and this becomes more relevant, when the body has already obtained a significant rest. Due to the fact that during the REM stage all of us dream, and those moments are of reparation and order of the mind, we conclude that dreaming rearrange and repair our organism to face in better conditions a new day.
Sleeping and dreaming
