Page 48 - More! 1_Student_s book

Sleep

Key words

What is sleep? Sleep is the body's natural 'pause button', body scientists
During sleep, the muscles relax, Breathing gets slow, muscles human
The heartbeat gets slow, The brain works differently too, breathing hibernate
heartbeat in danger
Why do we sleep? Scientists aren't sure, But they are sure
brain hunted
that sleep is very important for the brain and the body,

The different stages 01 sleep - Human [35-vear-old]

Read the text, Write the stages of sleep in the correct place on the graph,

Humans sleep in cycles
REM sleep
of about 90-120 minutes,
REM means 'rapid eye movement'. This is because the eyes
There are two types of move very quickly.
sleep: non-REM (four ,
The first rapid eye movement (REM) phase starts about 70 to
stages) and REM sleep, 90 minutes after a person falls asleep. People have between
three and five REM phases a night. They are not awake but the
Stage one brain is awake and active. People dream during REM sleep but
During this stage of sleep, the body cannot move. That stops people 'acting' their dreams.
you are not really asleep.
The body slows, the
muscles relax. It is easy .
to wake up from this type Sleep Stage ----')
of sleep. 1 1.=="'-'

Stage two
After ten minutes of light
sleep, you start 'true
sleep' This lasts about
20 minutes. People
breathe more slowly, the Hour I 2 3 4 5 6 7 8
heart beats more slowly.
Most sleep in the night is
'true sleep'.
Stage four
Breathing is rhythmic.
Stage three There is some muscle
Breathing and heartbeat activity. It is difficult to
are very slow now. wake up from this sleep. • You sleep about 8-10 hours.
• Human babies sleep about
16 hours a day.
• Old people sleep only 5-6
hours a night.
• Some animals sleep during
o Answer the questions,
the day. They are active
1 How many non-REM stages of sleep are there? dUring the night.
• Other animals (like the
2 When is the heartbeat at its slowest?
hedgehog) 'hibernate' - they
3 How many sleep cycles do people have each night? sleep for 3-4 months during
4 What part of the body moves when a person dreams? the winter.