What are the stages of sleep?
                     STAGES OF SLEEP
INTRODUCTION
Sleep is an important part of our lives. It 
improves physical and mental health. Sleep 
happens in stages, including REM sleep and 
non-REM sleep.
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Source: my.clevelandclinic.org 
What is sleep?
1. You may think nothing is happening when 
you sleep. But parts of your brain are quite 
active during sleep. 
2. And enough sleep (or lack of it) affects your 
physical and mental health. When you 
sleep, your body has a chance to rest and 
restore energy.
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Source: my.clevelandclinic.org 
Type of Sleep
1. During the night, you cycle through two 
types of sleep: non-rapid eye movement 
(non-REM) sleep and rapid eye movement 
(REM) sleep. 
2. Your brain and body act differently during 
these different phases.
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Source: my.clevelandclinic.org 
What happens in the 
brain during sleep?
1. We know that brain chemicals are very 
involved in our sleep cycle. 
Neurotransmitters are chemicals that help 
the nerves communicate. 
2. They control whether we’re awake or 
asleep, depending on which neurons (nerve 
cells) they’re acting on.
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Source: my.clevelandclinic.org 
Neurons
1. Neurons in the brainstem (where the brain 
and spinal cord meet) produce 
neurotransmitters called serotonin and 
norepinephrine. These chemicals keep our 
brain active when we’re awake.
2. Neurons located at the base of the brain 
are responsible for us falling asleep. It 
seems these neurons turn off the signals 
that keep us awake.
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Source: my.clevelandclinic.org 
Why do we need 
sleep?
1. Growth: In children and young adults, deep 
sleep (sleep that’s harder to wake from) 
supports growth.
2. Nervous system function: A lack of sleep 
affects our memory, performance and 
ability to think clearly.
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Source: my.clevelandclinic.org 
Why do we need 
sleep cont.
1. Survival: Researchers don’t fully 
understand why sleep is so essential. But 
studies in animals have shown that getting 
deprived of REM sleep can shorten 
lifespans.
2. Well-being: People who don’t get enough 
sleep are at higher risk for developing 
various health conditions including obesity, 
diabetes and heart problems.
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Source: my.clevelandclinic.org 
Stages of sleep
1. Non-REM sleep happens first and includes 
three stages. The last two stage of non-
REM sleep is when you sleep deeply. It’s 
hard to wake up from this stage of sleep.
2. REM sleep happens about an hour to an 
hour and a half after falling asleep. REM 
sleep is when you tend to have vivid 
dreams.
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Source: my.clevelandclinic.org 
Can we adapt to 
needing less sleep?
1. Generally, people don’t adapt to getting 
less sleep than they need. You may feel like 
you’re used to reduced sleep, but it still 
affects your function. 
2. For example, it can harm your judgment 
and reaction time.
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Source: my.clevelandclinic.org 
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