Stages of Sleep

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decreases. Stage 1 is light sleep where you drift in and out of sleep and can be

awakened easily. In this stage, the eyes move slowly and muscle activity slows.

During this stage, many people experience sudden muscle contractions preceded

by a sensation of falling. In stage 2, eye movement stops and brain waves

become slower with only an occasional burst of rapid brain waves. When a person

enters stage 3, extremely slow brain waves called delta waves are interspersed

with smaller, faster waves. In stage 4, the brain produces delta waves almost

exclusively. Stages 3 and 4 are referred to as deep sleep, and it is very

difficult to wake someone from them. In deep sleep, there is no eye movement or

muscle activity. This is when some children experience bedwetting, sleepwalking

or night terrors. In the REM period, breathing becomes more rapid, irregular and

shallow, eyes jerk rapidly and limb muscles are temporarily paralyzed. Brain

waves during this stage increase to levels experienced when a person is awake.

Also, heart rate increases, blood pressure rises, males develop erections and

the body loses some of the ability to regulate its temperature. This is the

time when most dreams occur, and, if awoken during REM sleep, a person can

remember the dreams. Most people experience three to five intervals of REM

sleep each night.

justify">Infants spend almost 50% of their time in REM sleep. Adults spend

nearly half of sleep time in stage 2, about 20% in REM and the other 30% is

divided between the other three stages. Older adults spend progressively less

time in REM sleep. As sleep research is still a relatively young field,

scientists did not discover REM sleep until 1953 when new machines were

developed to monitor brain activity. Before this discovery it was believed that

most brain activity ceased during sleep. Since then, scientists have also

disproved the idea that deprivation of REM sleep can lead to insanity and have

found that lack of REM sleep can alleviate clinical depression although they do

not

know why. Recent theories link REM sleep to learning and memory. Stage

Frequency (Hz) Amplitude (micro Volts)

BORDER-BOTTOM: #ece9d8; BACKGROUND-COLOR: transparent" vAlign="top"> Waveform type awake

BACKGROUND-COLOR: transparent" vAlign="top"> 15-50 <50 pre-sleep 8-12

PADDING-RIGHT: 3pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 3pt; PADDING-BOTTOM: 3pt;

BORDER-LEFT: #ece9d8; PADDING-TOP: 3pt; BORDER-BOTTOM: #ece9d8;

BACKGROUND-COLOR: transparent" vAlign="top"> 50 alpha rhthym

#ece9d8; BACKGROUND-COLOR: transparent" vAlign="top"> 1 4-8 50-100 theta 2

PADDING-RIGHT: 3pt; BORDER-TOP: #ece9d8; PADDING-LEFT: 3pt; PADDING-BOTTOM: 3pt;

BORDER-LEFT: #ece9d8; PADDING-TOP: 3pt; BORDER-BOTTOM: #ece9d8;

BACKGROUND-COLOR: transparent" vAlign="top"> 4-15 50-150

BACKGROUND-COLOR: transparent" vAlign="top"> splindle waves 3

justify">2-4 100-150 spindle waves and slow waves 4 0.5-2

BORDER-BOTTOM: #ece9d8; BACKGROUND-COLOR: transparent" vAlign="top"> 100-200

slow waves and delta waves

LINE-HEIGHT: 13.5pt; TEXT-ALIGN: justify">REM 15-30 <50 The waveform during

REM has low amplitudes and high frequencies., just like the waking state. Early

researchers actually called it "paradoxial sleep". The functions of many organ

systems are linked to the sleep

cycle.

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