It is a state of rest which affects both body and mind, where we are unconscious. In a healthy person, this follows a circadian rhythm(ie a daily cycle).
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Dreams - short definition
These are the images and emotions created by the unconscious mind during sleep.
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Why do we sleep ?
Inactivity theorystates that organisms have evolved sleep in order to protect themselves during periods that they would be vulnerable to predators. For example, people tend to sleep during hours of darkness.
Energy conservation theorystates that organisms sleep in order to cut the amount of energy being used.
Restoration theorystates that the point of sleep is to allow the body to repair and restore itself. According to Oswald (1966), REM sleep restores the brain and NREM sleep restores the body.
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Non REM sleep - stage 1
is the beginning of the sleep cycle
is a light stage of sleep
is a transition period between wakefulness and sleep
the brain produces very slow brain waves, the theta waves
it lasts only for a brief time
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Non REM sleep - stage 2
it lasts for about20 min
the brain begins to produce rapid, rythmic waves known as sleep spindles
body temperature starts to decrease
heart ratebegins toslow
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Non REM sleep - stage 3
brain produces deep, slow waves known as delta waves
is a transition period between light sleep and deep sleep
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Non REM sleep - stage 4
is adeep sleep
it lasts for about 30 min
bed-wetting and sleepwalking are most likely to occur at the end of this stage
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REM sleep - Stage 5
stage 5 is known as rapid eye movement sleep (REM sleep)
there are around 3-5 REM episodes a night (occupies 20-25% of total sleep in adults)
most dreaming occurs during this stage of sleep
increased respiration rate
increaced brain activity
muscles become more relaxed
is also referred to as paradoxical sleep
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Classwork
1. Describe REM sleep and Non-REM sleep.
2. After REM sleep is over, what usually happens to theh body?
3. After thinking about the different stages of sleep, what effects might sleep deprivation have on someone?
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