Lesson 5 of 6

Muscles in pairs

Goal: Explain how antagonistic muscles work.

Puzzles for this lesson

Muscles work in pairs. One muscle pulls a bone one way. Its partner pulls it back.

An antagonistic pair is two muscles that pull the same bone in opposite directions.
To bend the arm, the biceps contracts and the triceps relaxes.
To straighten the arm, the triceps contracts and the biceps relaxes.

Your turn

This lesson’s activity starts here in a moment.

I can describe how the biceps and triceps bend and straighten the arm.I can predict what happens when one of them contracts.

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Contract When a muscle gets shorter and fatter, and pulls

Relax When a muscle stops pulling

Antagonistic pair Two muscles that pull a bone in opposite directions

Biceps The muscle that bends the arm

Triceps The muscle that straightens the arm

For teachers: AQA 3.8.1 · Cambridge 8Bs.01