Sleep Physiology : What happens when you Sleep.Sleep Physiology : What happens when you Sleep. There are five stages of sleep that the human body goes through. A complete cycle takes an average of 9-10 Minutes. The sleep cycle begins from stage 1 and ends in REM (Rapid Eye Movement). The first sleep cycles have short REM sleeps and long periods of deep sleep. But later during sleep, REM periods lengthen and deep sleep time decreases. NON REM STAGES Stage 1. This is the period when you first fall asleep and you can be awakened easily. In this stage muscle activity slows and the eyes move slowly. People often experience sudden muscle contractions preceded by a sensation of falling from a height. Stage 2. In this stage eye movement stops and the brain waves become slower and there are bursts of rapid brain waves. Stage 3 In this stage brain waves called delta waves are mixed with smaller faster waves. Deep sleep begins in this stage. Stage 4 In this stage the brain produces only delta waves. There is no eye movement or muscle activity. This is the stage where children may experience bed wetting, sleepwalking or night terrors. In the REM period, breathing becomes shallow, irregular and rapid. Muscles in the limb are temporarily paralyzed. Blood pressure rises, heart rate increases, males develop erections and the body cannot totally regulate temperature. This is the period when dreams occur. Humans experience 3-5 intervals of REM sleep each night. Return From What Happens when you Sleep to About Sleep Page.
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