Stages Of Sleep:

What is sleep?

Sleep is a dynamic process during which the brain is very active and there are recognized stages of sleep, each of which is characterized by a different type of brain wave activity. Sleep is also one type of exercise which is very essential for your health.

What are the stages of sleep?

There are total five stages of sleep that cycle over and over again during a single night's rest; the stages are 1, 2, 3, 4 and REM that is rapid eye movement.
Stage 1 sleep is often described as first in the sequence, especially in models where waking is not included and polysomnography shows a 50% reduction in activity between wakefulness and stage 1 sleep. The eyes are closed during Stage 1 sleep, but if aroused from it, a person may feel as if he or she has not slept and stage 1 may last for five to 10 minutes.
Stage 2 is a period of light sleep during which polysomnographic readings show intermittent peaks and valleys, or positive and negative waves whereas these waves indicate spontaneous periods of muscle tone mixed with periods of muscle relaxation hence at this point, the body prepares to enter deep sleep.
Stage 3 and 4 are deep sleep stages where Stage 4 being more intense than Stage 3 and these stages are known as slow-wave, or delta, sleep. Especially during Stage 4, the electromyogram records slow waves of high amplitude, indicating a pattern of deep sleep and rhythmic continuity hence the body has entered deep sleep.
Stages 1 through 4 are also known as non-rapid eye movement sleep (NREM) while about 50% of sleep time is spent in stage 2 and about 20% is spent in REM that is normally more than 2 hours a night in adults.
Stage 5 which is also known as REM sleep is distinguishable from NREM sleep by changes in physiological states, including its characteristic rapid eye movements but however, polysomnograms show wave patterns in REM to be similar to Stage 1 sleep. In normal sleep the people without disorders of sleep-wake patterns or REM behavior disorder, their heart rate and respiration speed up and become erratic, while the face, fingers, and legs may twitch. Also intense dreaming occurs during REM sleep as a result of heightened cerebral activity, but paralysis occurs simultaneously in the major voluntary.

What are the different disorders of sleep?
There are more than 70 different sleep disorders that are generally classified into one of three categories that are lack of sleep, disturbed sleep and excessive sleep.

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