Page 17 - 新思维科学学生用书4 样章

1 Living Things

Muscles make us move

Bones are strong and hard. They

cannot bend, but your body can muscle A contracts muscle A relaxes
muscle A contracts
move in many ways.

All animals with skeletons have
muscles attached to the bones.

arm lifts
Muscles are the parts of the arm lifts
body that allow us to sit, stand, arm drops

walk, run, bend and stretch. muscle B relaxes muscle B contracts
muscle B relaxes
They make it possible for us
to smile, hold a pen, eat and talk.

Muscles are found under the skin.

They cover the skeleton and give

your body the shape that you have.

How muscles work

Muscles pull on bones to make
muscle A contracts
them move. Muscles work by muscle A relaxes
muscle A relaxes
getting shorter and longer.

When muscles get shorter they

pull on the bones they are
arm lifts
joined to. We say that the arm drops
arm drops
muscles contract. The pulling

movement allows you to move
muscle B contracts
muscle B relaxes muscle B contracts
and do the action that you want.
When muscles relax they get longer and let you rest.

Muscles always work in pairs. One muscle contracts

and pulls on the bone it is joined to. This makes the

bone move. The other muscle relaxes.

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