Contractile unit of muscle is?
ANSWER: (A) SarcomereREF: Guyton's physiology 22nd edition page 73The area between two adjacent Z lines is called a sarcomere. The orderly arrangement of actin, myosin, and related proteins that produce this pattern. The thick filaments, which are about twice the diameter of the thin filaments, are made up of myosin; the thin filaments are made up of actin, tropomyosin, and troponin. The thick filaments are lined up to form the A bands, whereas the array of thin filaments forms the less dense I bands. The lighter H bands in the center of the A bands are the regions where, when the muscle is relaxed, the thin filaments do not overlap the thick filaments. The Z lines transect the fibrils and connect to the thin filaments. If a transverse section through the A band is examined under the electron microscope, each thick filament is seen to be surrounded by six thin filaments in a regular hexagonal pattern.
Sarcomere
Sarcolemma
Myofibril
Sarcotubular System
Skeletal Muscle: Contraction and Excitation