Sleep Stages
These are the stages of sleep from going to sleep through into the dreaming stage and back out again
Sleep is broken down into 2 Categegories (REM and NREM) and 5 Stages.
(NREM)
Non Rapid Eye Movement - The Stages before dreaming
(REM)
Rapid Eye Movement - The Dream Stage
Sleep Stages in Detail
NREM (Non-Rapid-Eye-Movement, stages 1-4) and REM (Rapid-Eye-Movement, stage 5)
Characteristics of sleep stages
WAKE - may contain alpha rhythm i.e. an EEG frequency of 8-10 Hz
NREM (D-state sleep)
Stage 1 - Low amplitude EEG some theta rhythms (4-7 Hz;
Figure 2-7) and vertex waves Light sleep, muscles begin
to relax, breathing slow/irregular, heart rate decreases,
eyes slow rolling movement, person easily roused
Stage 2 - fragmented thoughts/images pass through mind(HI) True sleep, brain activity slows, eye movement ceases(usually) muscles relax, little movement
Stage 3 - ((Delta waves are present in all stages of sleep but become pronounced in stages 3 and 4. Delta waves are defined as waves with a frequency between 1.5 and 4.0 Hz and 0-4 waves per second.)) delta sleep or slow wave sleep(SWS) deep sleep slow brain waves (delta) interspersed small quick waves
Stage 4 - all delta waves (sleep walk expierienced) children
bedwetting
deepest stage of sleep, hard to arouse, this stage usually
occurs in the first third of the night, after which sleep
usually does not progress beyond stage 3.
REM (S-State sleeps) - 20% - dream, paralysed state (sp) brains o2 consumption increases. (penile erections associated too) body muscles stiffen, eyes move, heart rate increases, breathing rapid and irregular, blood pressure risesusually 2 hours a night
2 stages of REM only in specific research studies
Tonic REM - characterized by near paralysis and increased
cerebral blood flow
Phasic REM is characterized by irregular breathing, variable heart rate, rapid eye movements, and muscle twitches
1 cycle from stage 1 to REM takes around 90 mins
Percentage of sleep in each stage
Young Adults
(18-24) Percentage of total sleep
STAGE 1
STAGE 2
STAGE 3
STAGE 4
REM STAGE 2-5%
45-55%
10-15%
3-8%
20-25%
