2.4 Movement: muscles

Summary: Can you feel the muscle in the front of your arm working as you bend it? The muscle is pulling on one of the bones in your forearm lower arm, causing it to move up. Tags: science oxford-science student-book-7 biology Created: 2026-05-19 Last Updated: 2026-05-19

After this topic, you will be able to:

• describe the function of the major muscle groups
• describe how muscles cause movement in the body
• describe how antagonistic muscles control movement at a joint.

Think back

1. Name some joints in the body.
2. Which structure holds bones together?
3. How do muscles move bones?

Key idea Muscles contract (get shorter) to help us move. They can only pull.

Key words tendon, antagonistic muscles

Can you feel the muscle in the front of your arm working as you bend it? The muscle is pulling on one of the bones in your forearm (lower arm), causing it to move up.

Muscles in the body

Muscles are found all over your body. They are a type of tissue – lots of muscle Cells work together to cause movement.

There are many types of muscle in your body. For example, your heart is a muscle made of cardiac muscle tissue. This muscle pumps blood around the body.

Other muscles are found in your gut (intestine) and help move the food along. Figure 1 shows the major muscle groups in your body that are used for movement.

Figure 1Major muscle groups used for movement in the upper body. Full text alternative to the content

A Give three functions of muscles.

B Name three groups of muscles in the body used for movement.

How do muscles work?

To move, your muscles get shorter – they contract. Muscles are attached to bones by tendons. When a muscle contracts, it pulls on a bone. If the bone is part of a joint, the bone will move.

C Suggest what happens to the length of a muscle when it relaxes after contracting (getting shorter).

How do pairs of muscles work together?

Muscles can only pull. They cannot push. This means that two muscles have to work together at a joint. If you only had one muscle in your arm, you may be able to bend your arm, but you would not be able to straighten it again.

At each joint, a pair of muscles works together to cause movement. These are called antagonistic muscles. When one muscle contracts, the other muscle relaxes.

The biceps and triceps are an example of a pair of antagonistic muscles. These are used to bend and straighten the arm at the elbow joint.

To bend the arm, look at Figure 2:

• the biceps muscle contracts
• the triceps muscle relaxes.

Figure 2The biceps muscle contracts to bend the arm.

To straighten the arm, look at Figure 3:

• the biceps muscle relaxes
• the triceps muscle contracts.

Figure 3The triceps muscle contracts to straighten the arm.

Literacy skills Design a model to show how antagonistic muscles allow your leg to move. Present your model to a partner. Explain how it represents antagonistic muscles.

Figure 4

1. Copy and complete the sentences. Muscles are attached to bones by ligaments/tendons. When a muscle contracts/relaxes, it shortens and pulls/pushes on a bone. If the bone is part of a joint/organ, this will cause the bone to move. Pairs of muscles work together to control movement at a joint. They are called antagonistic/cartilage muscles.
2. Describe the difference between a tendon and a ligament.

Figure 4

1. Look at Figure 4, which shows the main muscles of the human leg. Predict what happens when muscle B contracts.Predict what happens when muscle C contracts.Explain why antagonistic muscles C and D are required for movement at the ankle. Figure 4 Full text alternative to the content