APPLIED RADIOLOGICAL ANATOMY

Detailed explanation-1: -Skeletal muscles usually work in pairs. When one muscle contracts the other relaxes and vice versa. Pairs of muscles that work like this are called antagonistic muscles. For example, the muscles in the upper forearm are the biceps and the triceps are antagonistic.

Detailed explanation-2: -When one of them contracts, the bone is pulled in that direction and the other muscle of the pair relaxes. To move the bone in the opposite direction, the relaxed muscle contracts and the first one relaxes. Thus two muscles have to work together to move a bone.

Detailed explanation-3: -To straighten the arm, the biceps relax while the triceps contract.

Detailed explanation-4: -Contraction of biceps brachii flexes the lower arm while the contraction of triceps brachii extends it.

Detailed explanation-5: -The biceps and triceps act against one another to bend and straighten the elbow joint. To bend the elbow, the biceps contracts and the triceps relaxes. To straighten the elbow, the triceps contract and the biceps relax.