Function: How the Body Moves

Movement of the body depends on the interaction of muscles, bones, and joints in response to signals from the brain and nerves. A muscle typically connects two bones and crosses the joint between them. When a muscle contracts, it pulls on the bones to which it is attached and produces movement. Muscles can only pull, not push. Therefore, many muscles are arranged in pairs, one on each side of a joint, so that they produce opposing movements. An example is the pairing of the triceps and biceps muscles in the upper arm.

Straightening the arm

The triceps and biceps muscles cross opposite sides of the elbow joint. While the triceps muscle contracts to pull down the bones of the forearm, the biceps relaxes.

Bending the arm

To bend the arm, the biceps muscle contracts to pull up the bones of the forearm, while the triceps relaxes.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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