Page 16 - 新思维科学学生用书6 样章

1.1 The circulatory system

Heartbeat and pulse

Your heart beats about 90 times a minute. When

you are grown up it will beat about 70 times a minute.
When you run around, your body needs a lot more

food and oxygen. The more active you are, the more

often your heart needs to beat to supply enough food
particles and oxygen from the blood.

You can count your heartbeats by feeling your pulse.
Your pulse is caused by the pressure of the blood as

the heart pumps it to the rest of the body.

Two good places to find your pulse are on the side of
your neck and the inside of your wrist. When you find

your pulse you will feel a small beat under your skin.

Each beat is caused by the contraction of your
heart muscle.

Think like a scientist 1

Measuring pulse rate

You will need:

a watch or timer that can time seconds

1 Find your pulse on your wrist or neck.

2 Count how many beats you feel in

one minute.
Repeat this three times.

3 Record the results in a table. Is the

number of beats the same each time?
4 Compare your measurements with

others in your class.

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