When the heart beats, when partially digested food moves through the intestines, and when the body moves in any way, muscle is involved. These many and varied functions of the muscular system are performed by three distinct types of muscle (see figure 1.1): smooth muscle, cardiac muscle, and skeletal muscle. Smooth muscle is sometimes called involuntary muscle because it is not under direct conscious control. It is found in the walls of most blood vessels, allowing them to constrict or dilate to regulate blood flow. It is also found in the walls of most internal organs, allowing them to contract and relax, for example to move food through the digestive tract, to expel urine, or to give birth.
Exercise requires movement of the body, which is accomplished through the action of skeletal muscles. Because exercise and sport physiology depends on human movement, the primary focus of this chapter is on the structure and function of skeletal muscle. Although the anatomical structures of smooth, cardiac, and skeletal muscle differ in some respects, their control mechanisms and principles of action are similar.
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Tropomyosin is a tube-shaped protein that twists around the actin strands. Troponin is a more complex protein that is attached at regular intervals to both the actin strands and the tropomyosin. This arrangement is depicted in figure 1.5. Tropomyosin and troponin work together in an intricate manner along with calcium ions to maintain relaxation or initiate contraction of the myofibril, which we discuss later in this chapter
Having reviewed the overall structure of muscle and the process by which it develops force, we now look more specifically at how muscle functions during exercise. Strength, endurance, and speed depend largely on the muscle’s ability to produce energy and force. This section examines how muscle accomplishes this task. Check out the best entertainment source ifuntv. You can also visit here to get the latest headline news around the world listinside. If you need more information about 0x00x0, you can get essential news from it.
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