The single units that make up a muscle are

The single units that make up a muscle are called muscle fibers. These muscle fibers are long, cylindrical cells that contain multiple nuclei. They are grouped together into bundles called fascicles. Each muscle fiber is made up of smaller units called myofibrils, which are composed of even smaller units called sarcomeres. Sarcomeres are the basic contractile units of muscle fiber and are made up of two types of protein filaments: actin (thin filaments) and myosin (thick filaments). The interaction between these filaments during muscle contraction leads to the shortening of the muscle fiber, resulting in muscle movement.