The Physiology of sleep Is characterized by two phases, REM and NoREM, and within the REM phase there are four stages.
Adults usually have about 8 hours of sleep per day. If the 8 hours are carried out in a continuous way, it will take about 4 or 5 cycles.
Each cycle can be understood as complete phases of sleep (from stage I to stage REM), and can last between 90 and 120 minutes each.
What does sleep consist of?
When we talk about sleep or the process of sleeping, we refer to a physiological and natural state in which the level of alertness and vigilance is diminished, since the person is resting.
And even if it seems that the external stillness of the subject, makes the inner level is in a state of tranquility, it is totally wrong, because internally the body of the sleeping does not stop and continues to function as complex as when we are awake.
The dream is composed of different degrees of intensity or depth, where in turn there are modifications of the organism that accompany each phase or stage of sleep.
Basic Theories of Sleep
One of the first theories formulated to understand the dream process was the Passive Sleep Theory, formulated by Bremmer in 1935. This theory was based on the fact that the brainstem Were exhausted throughout the day, so when it was time to sleep, they were tired and deactivated.
It would be something like the battery of your mobile, taking the fact of loading it as our sleeping process.
But after several years and some experiments the theory became obsolete and began to have a different vision. Nowadays the theory that accompanies this process says that sleep is produced by active inhibition.
This means that in the brain There is a small area that causes parts of it to be deactivated during sleep. Something like a watchman who prevents other brain areas from doing their work while you sleep.
But you have to be clear that the brain does not sleep while you do it, but your way of working changes to be in line with the process.
To this day, it is not yet known what is the physiological purpose that creates the need that any living being has to sleep. As you read above, sleep is considered a priority need, and even the fact of not sleeping for a while can cause disorders And even death though it sounds incredible.
People can not sleep anything for anything from 1 to 2 nights. From the third night without sleep, they would appear disorders that would gradually increase in gravity and they would have serious consequences . This would affect areas such as attention, memory, State of mind And even hallucinations and seizures may occur.
Stages of sleep
There are 4 phases of the sleep process Of non-REM (NREM) and one of REM sleep.
NREM Phase
This stage is also known as No-rem , Comes from the English translation"non-rapid eye movement", this first stage is the first contact with the dream.
It is the first state of reverie in which we enter and for most adults will be the place that occupies 75% of the totality of their dream.
The NRem stage is divided in turn In 4 phases , In which the characteristics of the dream are molded, are the following:
Stage NREM- Phase 1
It is the stage where we are drowsy or sleepy. The waking state is disappearing as the Alpha rhythm It also does. At the moment the muscle tone does not relax completely. Beta waves are gone.
Stage NREM- Phase II-III
It is the stage where even though we are asleep, the sleep is light, more and more the alpha rhythm disappears, there is still muscle tone. We slowly experience the entrance to the theta waves.
Stage NREM- Phase IV
This is the stage of deep sleep, the encephalographic rhythm is very low, the muscle tone is maintained or may be greatly diminished. In our brain appear Waves Delta .
Actually these stages differ in that the muscular atony is gradually increasing and the brain waves are gradually changing depending on the relaxation of the body.
REM phase
This is the phase of paradoxical sleep, because during this phase the brain has an activity that resembles that which occurs when we are awake. In addition, rapid eye movements are observed during this phase. The body is in slumber.
What we dream about is during this phase.
To date, there is no clear theory of why eye movement occurs during the REM phase.
How is sleep organized during the night?
Adults usually have about 8 hours of sleep per day. If the 8 hours are carried out in a continuous way, it will take about 4 or 5 cycles.
Each cycle can be understood as complete phases of sleep (from stage I to stage REM), and can last between 90 and 120 minutes each.
The distribution is normally as follows:
- Phase I during the cycle would be developing about 1.5% of the total cycle. This means that if the cycle lasts 100 minutes, only 1 and a half minutes the body would be in phase I.
- Phase II during the cycle would be present about 25% of the total cycle. In a cycle of 100 minutes, 25 minutes would be the phase II would last.
- Phases III and IV during the cycle would last 45% of the total cycle. In a cycle of 100 minutes, these phases would last approximately 45 minutes.
- The REM phase during the cycle would have a duration of 25% of the total cycle. So in a cycle of 100 minutes, only 25 minutes correspond to the paradoxical dream and dreams.
How much do people sleep?
The distribution of sleep throughout the day are different according to several factors such as age, daily activity, health, etc...
Babies sleep most of the time, although as the child grows, waking states are getting longer. It is curious to know that babies have a higher percentage of REM sleep than adults, and it is throughout childhood that percentage will begin to fall to reach a normalized percentage.
In adults, the need for sleep is lower than in infants. An adult can sleep between 5 and 9 hours and have a good performance throughout the day. Although it is always advised to sleep 7 to 8 hours a day for good health and quality of life .
Different times of life and vital situations can cause the amount of sleep to be reduced. For example, when we go through moments where we have a lot of intellectual activity, we will need more sleep than at times when the stress Is very present in our life.
Older people have less need for sleep and their rest periods are less. They usually wake up at night and the percentage of phase IV sleep. However the REM phase seems invariable throughout life in terms of its duration in the sleep cycle.
The dream is governed by a biological clock
The sleep process is governed by a biological rhythm comprised as Circadian rhythm . These are 24-hour cycles that are related to day and night.
The circadian rhythm of sleep and wakefulness is every approximately 25 hours. This fact is curious because this indicates that we are programmed so that we let ourselves be influenced by a certain rhythm or cycle.
In our central nervous system there is one of our biological clocks. This watch makes non-REM sleep and REM sleep last for a certain time.
The circadian rhythms depend on the interaction of the organism with the stimuli that come from outside. Of these external stimuli the most important and the one that most influences us is the light, as well as the time to wake up, since this hour can be fixed strictly.
The time at which we go to sleep is also important, and although we can fix some routine guidelines that make us at a certain time we are in bed, we usually can not decide the exact moment we fall asleep.
If the person is totally isolated from these stimuli, that is to say, that does not perceive changes of light, temperature, activities, etc... would also follow a normal biological rhythm of sleep, since the human body is programmed to follow the rhythm that we need without Need for external influences.
Dreams
When we dream our brain does not rest just like us, because the brain activity continues in constant and active movement.
Also while we sleep we have some curious experiences, called dreams or more commonly known as dreams.
As you read above, dreams occur during the REM phase (hence many experts think that eye movement occurs as a result of those dreams) and are in color and in motion, as if we were watching a movie.
During the deep sleep phase, sometimes you also dream. The only difference is that these dreams are more abstract type.
During REM sleep, the reticular system, which is related to the brain and the brain, is activated in our brain. Forebrain . These structures are also activated when we are awake. These structures are involved in sensory stimulation, so when activated it explains why when we dream we have the sensation of actually living that dream. We can even feel what we dream.
Also during sleep the limbic system is also active, with structures such as the amygdala, and the cyngular cortex. This system takes care of the emotional life, so this can also give a rational explanation of why during sleep we not only feel sensually what we are dreaming, but also feel it emotionally.
During sleep, the prefrontal cortex, which is responsible for mental reasoning, is inhibited, so this can give us relevant information about the little logic that our dreams often have.
I hope this article has provided you with information you did not know about the natural sleeping process you do every night.
To finish with the article I leave you here 6 curiosities about the dream that maybe you did not know.
6 curiosities about the dream
- The blind also dream: Those who were born blind can dream just like the people they can see. The difference is that the dreams of the blind are represented by other senses such as sound and smell.
- Women dream of sex the same amount as men do: Women dream of sex just as men do. In equal conditions of both quantity and frequency. Perhaps the difference is only in content.
- Not everyone dreams of color: 12% of people dream in black and white. This fact is curious, because it is said that since the television appeared people previously dreamed in black and white and it was after the apparition when we started to dream color.
- The animals also dream: Surely if you have any companion animal, sometime while you slept you noticed that it moved as if it were doing something. Animals like us humans also have dreams of fact while they dream, they have the same type of brain waves as us.
- Your body reacts to your dreams as if they were a real experience: The experience that we live during the moment in which we dream is recorded as if it were a real experience, the difference is that you truly know that it was a dream, but your brain has difficulty assimilating it and processing it that way .
- We only dream of the faces we already know: Your brain does not invent faces when it comes to dreaming. When we dream with people, the faces that show these are faces of real people that we have seen during our life. We may not remember the face or that we do not know the person, but it is certainly part of a memory.