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Muscular System How do muscles work? • Muscles can't push. They pull. • Muscles often work in pairs so that they can pull in different or opposite directions, like a finger that moves in different directions. Muscular System: Involuntary/Voluntary • The muscular system moves the body. • The body has over 600 muscles. • Some muscles are called voluntary, that means that you choose to use them. How active you are depends on how much use they get! • Some muscles are called involuntary because they work without you thinking about them. These are muscles like the heart and digestive system. • Ligaments are strong connective tissue that attaches muscle to bone. Function of Muscles • • • • Produce movement Maintain posture Stabilize joints Generate heat The Muscular System Muscles are responsible for all types of body movement Three basic muscle types are found in the body Skeletal muscle Cardiac muscle Smooth muscle Skeletal Muscle Characteristics • Most are attached by tendons to bones. Skeletal Muscle Characteristics • • • • Cells are multinucleate Striated – have visible banding Voluntary – subject to conscious control Cells are surrounded and bundled by connective tissue Cardiac Muscle Characteristics • Has striations • Usually has a single nucleus • Joined to another muscle cell at an intercalated disc • Involuntary • Found only in the heart Smooth Muscle Characteristics • • • • Has no striations Spindle-shaped cells Single nucleus Involuntary – no conscious control • Found mainly in the walls of hollow organs Comparison of Types of Muscle - The Muscular System Muscles at Work • Because muscle cells can only contract, not extend, skeletal muscles must work in pairs. While one muscle contracts, the other muscle in the pair relaxes to its original length. Effects of Exercise on Muscle Aerobics result in stronger muscles due to increase blood supply Muscle fibers increase mitochondria and oxygen storage Muscle becomes more fatigue resistant Heart enlarges to pump more blood to body Does not increase skeletal muscle size Effects of Exercise on Muscle • Results of increased muscle use from resistance training • Individual muscle cells make more contractile filaments & connective tissue increases – Increase in muscle size – Increase in muscle strength