| Added | Sun, 20/08/2017 |
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Sleep is a natural physiological process of stay in a condition with minimal level of brain activity and reduced reaction to the world around us.
Sleep is essential to person to ensure the rest of the body, processing and storage of information, elaboration of unconscious models of expected events, organism's adaptation to changing light conditions (day and night) and recovery of immunity. In normal adult and healthy person it should last about 8 hours but depending on the situation this period can be from 4 to 10 hours. The sleep normally, sleep occurs cyclically, roughly every 24 hours. These cycles are called circadian rhythms.
Just before sleep induces a state of drowsiness, reduced activity of the brain. It is characterized by a decreased level of consciousness, yawning, lowering of the sensitivity of sensory systems and the secretory activities of glands (as a consequence of the sticking of the eyelids), as well as the change in heart rate.
The structure of the dream consists of a series of steps, regularly repeated during the night, the appearance of which is due to the activity of different brain structures.
In a healthy person the dream begins with the first stage of NREM sleep (Non-REM sleep), which lasts 5-10 minutes. Then comes stage 2, which lasts about 20 minutes. Even 30-45 minutes is between 3-4 stages. After that, the sleeper returns to the 2nd stage of NREM sleep, after which there is the first episode of REM sleep, which has a short duration – about 5 minutes. This entire sequence is called a cycle. On average, healthy sleep is celebrated for five full cycles. REM sleep cycle-to-cycle is lengthened, and the depth of sleep decreases.
If during REM sleep stage to Wake up the sleeping, then in 90% of cases you will hear a story about a vivid dream.
Translated by «Yandex.Translator»
Ten seconds of five typical EEG various States of sleep and wakefulness.
Translated by «Yandex.Translator»
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