Final answer:
The arm muscles, such as the biceps and triceps, move the forearm through contraction and relaxation, with tendons connecting the muscles to the bones. The biceps contract to flex the arm, while the triceps contract to extend it. Muscles work in pairs and create efficient force for movement.
Step-by-step explanation:
Our arm muscles cause our forearm bones to move through the contraction and relaxation of muscles. This process involves the tendons, which are tough bands of connective tissue that connect muscles to bones. When muscles like the biceps brachii contract, the tendons pull on the bones and cause movement. In the case of the arm, when the biceps contract, the forearm moves upwards in a curling motion because the biceps are flexor muscles, meaning they close the limb.
Muscles work in pairs because they can only contract, not extend. The biceps and triceps are such a pair involved in moving the forearm. While the biceps are flexors, the triceps are extensor muscles that open the limb or extend the arm. When the triceps contract, they pull the arm back into an extended position.
Bones, muscles, and joints work together as simple machines where the input force by muscles is much greater than the output force due to mechanical advantages much less than one. This system allows for efficient movement and use of force within the body.