The Different Stages of Sleep
Stage 1 Non-REM Sleep
After the sleeper falls asleep, he or she enters into what is known as the Stage 1 of non- REM sleep.
Stage 1 sleep is the period we "drift off."
Stage 1 NREM Sleep is characterized by the following:
Generally, this description of bodily functions characterizes all non-REM sleep.
|Breathing becomes slow and even|
|The heartbeat becomes regular|
|Blood pressure falls|
|Brain temperature decreases|
|Blood flow to the brain is reduced|
|Little or no body movement.|
Stage 1 sleep might be called a kind of twilight time. It's initial appearance lasts up to ten minutes in most sleepers.
Brain waves become smaller, slower, and somewhat irregular characterized by a low-voltage fast EEG.
This portion of sleep is distinguished by drifting thoughts and dreams that move from the real to the fantastic, along with a kind of floating feeling.
The sleeper is still easily awakened and might even deny having slept.
Examples of EEG Patterns
associated with the stages of sleep and the time course of sleep stages.
Stage 2 NREM
Stage 2 is an intermediate stage of sleep. It initially lasts about twenty minutes. The sleeper will gradually descend deeper into sleep, becoming more and more detached from the outside world and progressively more difficult to awaken.
Stage 2 is characterized by:
|Larger brain waves and occasional quick bursts of activity.|
|The sleeper will not see anything even if the eyes are opened.|
|A sleeper can easily be awakened by sounds.|
|Bodily functions slow down. Blood pressure, metabolism, secretions, and cardiac activity decrease.|
Stage 3 NREM
Stage 3 is the beginning of deep sleep, occurring about thirty to forty five minutes after you first fall asleep.
Stage 3 is characterized by:
|Brain waves are slow (at the rate of 0.5 to 4 per second) and quite large (five times the size of waves in Stage 2). These brain waves are known as delta waves.|
|The sleeper is far more difficult to awaken as compared to stage 1 or 2 sleep. It takes a louder noise or an active attempt to wake him or her.|
Stage 4 NREM
The deepest sleep occurs in Stage 4.
Stage 4 is characterized by:
|The brain waves (called delta brain waves) are quite large, making a slow, jagged pattern on the EEG.|
|The sleeper experiences virtual oblivion. If the sleeper is a sleepwalker or a bed wetter, those activities will begin in this phase.|
|Bodily functions continue to decline to the deepest possible state of physical rest.|
|This first period of deep sleep is the deepest. The sleeper awakened from deep sleep will probably be groggy, confused, or disoriented. He or she may experience "sleep inertia" or "sleep drunkenness," seeming unable to function normally for quite some time.|
After the first phase of deep sleep ends, the sleeper returns to Stage 2 and then enters the REM state.
Next Topic: REM Sleep Stage
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