Sleep stages

hypnogramme d'un sommeil normal
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Sleep is not just about having dreams as many people believe. It is a special time when the body can heal, digest foods, fix and renew body cells, maintain itself and rest. Dreams are only a small part of this. In fact, sleep is divided into various sleep stages, which were first discovered in the 1950s. Two major stages exist – NREM (asquiet type sleep) and REM (asactive or paradoxical sleep), but these are broken down further into four stages which are repeated all night long.

Sleep stages in the early levels occur when a person is still somewhat alert and just barely awake. A person’s brain begins producing beta electrical waves which a very fast and small. Then, as the brain relaxes and gradually slows down, it produces alpha electrical waves which are considerably slower than the beta ones. In the moments just before a person falls asleep, some people get odd sensations and even hallucinations, even with their eyes closed. Some people have felt like they are falling. Others see images when their eyes are closed, vivid and even moving scenes. Even more people may hear voices or someone calling them by name. However, contrary to popular belief, this is not a sign of mental health problems. However, one of the most common sensational events that happen in the moments before the person is completely asleep is the myoclonic jerk. It has been described by those that see it as twitches in the sleeper’s body and similarly by the person themselves. They are in fact very common.

Stage 1 Sleep

The start of any sleeping cycle is the lighter stage. It is the transition between wakefulness and sleep where the brain produces theta electrical waves that are extremely slow and high in amplitude. Usually, this stage lasts for about five to ten minutes. However, if you wake a person in this stage, they will usually claim to have never been asleep at all.

Stage 2 Sleep

The second sleep stage lasts for about twenty minutes with the brain producing rhythmic and rapid electrical type brain waves in bursts that are commonly called sleep spindles. At this point, the heart rate slows and the body temperature decreases.

Stage 3 Sleep

The third sleep stage transitions the body between lighter sleep and much deeper sleep. The brain begins producing some much deeper and slower brain electrical waves than ever before – delta waves – near the end of this stage.

Stage 4 Sleep

The fourth stage is where the brain is only producing delta type electrical waves that continue for about thirty minutes. It is quite normal for people to sleepwalk or wet their beds near the end of this stage.

Stage 5 Sleep

The final sleep stage or the paradoxical sleep is the one that most people remember – the dream stage. This stage is characterized by REM or rapid eye movement sleep. The breathing rate increases and the body’s systems and brain become very active, though the muscles relax even more. It is believed that dreams happen in this stage because of the brain’s increased activity and that the muscles in a sense become almost paralyzed.

The Process of Sleep Stages

Sleep stages do not progress beyond stage four in exact order. After stage four, the process generally reverses to stage 3, stage 2 and then repeated again without stage 1 by going into a REM type sleep. Every time the body has completed the REM cycle, the body goes back to stage 2. This repeated process usually continues through the night about four or five times. Usually, REM type sleep occurs about ninety minutes after a person falls asleep. Early REM cycles are shorter and gradually increase in time duration with each repeated cycle. REM can last as long as one hour in repeated cycles. Therefore, any disruption in these sleep patterns can cause sleep disorders and prevent the body from going through necessary maintenance and rest periods that it needs for energy regeneration for the next day of waking.

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