ANATOMY

Detailed explanation-1: -Muscles can only contract. They cannot actively extend, or lengthen. Therefore, to move bones in opposite directions, pairs of muscles must work in opposition. For example, the biceps and triceps muscles of the upper arm work in opposition to bend and extend the arm at the elbow (see Figure below).

Detailed explanation-2: -Muscles can only contract. They cannot actively extend, though they can move or relax back into the non-contracted neutral position. Therefore, to move bones in opposite directions, pairs of muscles must work in opposition. Each muscle in the pair works against the other to move bones at the joints of the body.

Detailed explanation-3: -Skeletal muscle constitutes the majority of muscle mass in the body and is responsible for locomotor activity. Smooth muscle forms blood vessels, gastrointestinal tract, and other areas in the body that produce sustained contractions. Cardiac muscle make up the heart, which pumps blood.

Detailed explanation-4: -Assertion [A] : Muscles can only pull on structures not push. Reason [R] : Skeletal muscles are often arranged in pairs that pull bones in opposite directions.

Detailed explanation-5: -Muscles move our bodies. To do so, they contract, which then generates movement. Share on Pinterest Muscles use energy from our food to produce movement.