Sleeping is one of the most important activities in human life, an apparent state of tranquillity where our body is working actively to rest the body, eliminate toxins and strengthen various cognitive functions, which is essential for the well-being of our entire body.
This is a physiological process involving the central nervous system and the autonomic system, the architecture of which is a cycle consisting of five phases: in order to achieve a restful effect, it is necessary to wake up when the cycle is complete. However, the cycles are not all the same and the proportion between the phases varies with the passing of the hours.
Let’s take a look at the sleep phases that make up a cycle.
PHASE 1: falling asleep
This is the lightest phase in which the gradual transition from wakefulness to sleep takes place. It is characterised by a lowering of body temperature, relaxation of body muscles and a slowing of the heartbeat. In this phase, eye movements are not rapid, indicating a slow decrease in brain activity.
This phase lasts on average between 5 and 10 minutes.
STEP 2: light sleep
In this phase the body prepares to recharge its energy and enter deep sleep, further decreasing body temperature and slowing the heart rate. Eye movements are almost completely absent, muscles are relaxed and breathing is very deep.
STEP 3: deep sleep
With the third phase you enter deep sleep, in which you are completely asleep and eye movements are completely absent. If you are awakened during this phase, you may experience a feeling of confusion and disorientation, as your metabolism is very slow and brain waves are large.
STEP 4: effective deep sleep
This is the deepest phase of sleep. The body temperature drops further and the movement of the eyes is irregular, moving back and forth with closed eyelids. The 4th phase is crucial as it is during these minutes that the body regenerates and restores metabolic reserves.
During this last stage of the cycle, blood flow, brain activity and respiration gradually increase. It is also defined as a “paradoxical” phase of sleep, because despite being in a phase of deep sleep, the brain is active as when you are awake: this is also confirmed by the fact that oxygen and glucose are consumed as if you were performing an intellectual activity. The muscles of the legs and arms go through a short period of paralysis, while the eyes move very quickly, a characteristic activity that gives this phase its name “Rapid Eye Movement“.
It is the phase in which you mainly dream, or more precisely, you most often remember what you dreamt. If you wake up during this phase you are fully oriented and remember the dream well.
The REM phase is thought to play a central role in the processing of lived experiences and long-term storage.
At the end of the REM phase, which varies in duration but does not exceed 15 minutes, a new sleep cycle begins.
REM and non-REM phases alternate about 4 or 5 times during the course of a single night, and have a total duration of about one and a half hours. Every single phase carries out an important task for our body: if we sleep too little or wake up very frequently during the night, the phases fail to perform their functions and this has repercussions on our body.