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When I started to run up and down the
stairs…
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This was detected by my brain which
sent nerve impulses to the heart.
6
Glucose reacted with oxygen, releasing
energy. At the same time, carbon
dioxide and water were produced.
The heart started to beat faster and
harder to move my blood faster.
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The energy needed for this was replaced
by a chemical reaction in the muscle
cells called respiration.
My heart rate went back to normal.
Very soon, my muscle cells started to
run short of oxygen and acidic carbon
dioxide started to build up in the blood.
My heart and blood system was able to
supply enough oxygen to the muscle
cells.
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10
5
When I stopped running up and down
the stairs, the respiration in my muscle
cells slowed down.
4
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My leg muscles contracted to lift my
body.
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What does it mean to be fit?
If you are fit, your body is well set up for exercise.
For exercise your muscle cells need energy.
Where does this come from?
carbon dioxide
oxygen
respiration
water
glucose
energy
Which organ systems provide the things you need for
respiration?
Why does your pulse change when you do some activities?
Which activity gave the highest pulse rate?
What sort of activity would give you a higher pulse rate?
What might you be doing if you had a lower pulse rate?
When your heart is beating faster, what is happening in your
body?
Why do different people have different pulse rates?
What process is
this animation
showing?
Where is it
happening?
How is this linked
to fitness and
stamina?