Multiple choice Which term describes the units of associated thick and thin fibers? Sarcomeres Actinomeres Mycomeres Muscle Bundles Reveal answer Fill a bubble to check yourself A Correct answer Explanation A sarcomere is the basic functional and structural unit of a muscle myofibril, composed of organized arrays of overlapping thick (myosin) and thin (actin) filaments. It is bounded by Z-lines and shortens during muscle contraction.