Every muscle fibre is made from thin strands called myofibrils . Under a microscope, the strands look striped, which is why this kind of muscle is called striated or striped. The stripes are actually alternating filaments of two substances called actin and myosin , and it is these that are the key to muscle power. At a signal from the brain, the myosin and actin filaments are drawn together, making the muscle shorter. As the muscle shortens, it pulls on the bone, making the movement.
Cardiac muscle is the muscle in the heart.
It beats automatically, though its rate is adjusted by chemical and nervous signals to match demand. Smooth muscle occurs in moving soft tissue inside your body, contracting blood vessels to control blood flow or rippling around the gut to push food through. How muscles work Muscles do everything from the twitching of an eyebrow to a jump in the air. Indeed, muscles can only contract, not make themselves longer. So each time a muscle contracts to make a movement, it must be pulled back to its original length by another muscle contracting.