Why do we spend at least a third of our lives doing an activity that goes so fast?Numerous studies have been conducted on the sleep phases to clarify these two issues. Sleep is a very important behavior in our lives. We are talking about the urgent need, to sleep that forces us to find a quiet, cozy and comfortable place to stay a few hours.
The waiting function seems to be important. If we avoid sleep, the body starts to insist that we do it, studies show that if we do a lot of physical exercise sleep will not change, on the other hand, after intense mental activity, the body needs to sleep more.
- This is because the main function of sleep is to allow the brain to rest and recover from the mental activity exerted during the day.
- The rest of the brain is so important that if this process doesn’t happen.
- According to animal studies.
- We know it would die.
We know that sleep is structured in a series of phases that we will explain below, so we will immerse ourselves in the five phases of sleep.
Sleep is divided into five phases called I to IV plus REM sleep (fast eye movement ?, rapid eye movement ?, free translation). From the beginning of sleep, these phases appear in an orderly fashion until reaching the REM phase, then, throughout the night, the non-remy sleep periods are modified by PERIODS of REM sleep, each of these cycles lasts about 90 minutes. Therefore, in an eight-hour sleep period, four or five cycles will occur.
The sleep phases have been discovered through various studies in sleep laboratories, are differentiated by the mental activity recorded in an EEG (electroencephalogram) and by various physiological actions, then we will detail what happens in each phase of sleep.
This is the first phase of sleep. When a person closes his eyes and notices a feeling of drowsiness, he is at this stage, here we have a conscious individual able to react to environmental stimuli, in fact it is a transition phase between awakening and sleeping.
Physiologically, we face theta brain waves, which means that EEG activity begins to synchronize. Although it is still irregular, it is not as much as the wakefulness of the brain, if we look into an individual’s eyes at this point we will see how they open and close from time to time and how they move up and down.
After 10 minutes in Phase I, the sleeping individual enters Phase II and now sleeps soundly. But if the individual wakes up at this point, he will not remember sleeping, he will insist that he was awake all the time, it is a preparatory phase for the true conciliatory dream of phases III and IV.
Physiologically, we have an irregular electroencephalogram with episodes of theta waves, if an auditory stimulus occurs at this stage, a brain wave called a K complex. This wave appears to represent a process of auditory inhibition that prevents the individual from waking up.
After 15 minutes of phase II, the individual begins phase III. This is the stage at which restful rest actually occurs. Phases III and IV are very similar, there is only one change in sleep depth and effectiveness.
In this phase we present a slow-wave EEG. This means that brain activity is highly synchronized and relaxed. We have a great inhibitory neural activity, to prevent the individual from waking up. This phase is also very important for memory consolidation and learning processes.
The REM phase arrives after 45 minutes of slow sleep, the opposite of the other phases. We are here in a state similar to awakening, brain activity is out of sync and accelerated, although it is difficult to awaken a person at this point, an important stimulus (such as saying the person’s name) will wake him up. much shallower than slow sleep.
In this phase, the individual’s eyes move rapidly in all directions (hence the name of the phase) and there is a strong loss of muscle tone, the individual is paralyzed, this paralysis is due to that during the REM phase, dreams Y to prevent the individual from imitating what he is doing in his dreams, there is a disconnection with the muscles.
Another curious fact of the REM phase is that there is a genital activity that results in vaginal lubrication in women and an erection of the penis in men, without sexual arousal. This characteristic of REM sleep has been used in the clinical field to distinguish whether the causes of impotence is psychological or physiological.
The function of the REM phase is still not entirely clear, this is an important phase, since when the individual, for some reason, does not go through this phase of sleep, the body tries to compensate for this future lack of sleep. function related to the consolidation of memory and learning, but even so, much remains to be known about this paradoxical phase of sleep.