The Muscular System

Functions of the Muscular System The muscles in your body are always at work Muscle make you breath, make your heart beat, and help you move food through the digestive system These involuntary processes happen without you controlling them When you throw a ball or run in a game you are using muscles that are under voluntary control Without the use of muscles you would be unable to perform any of these tasks

Structure of Muscles Muscles are made of long cells called fibers Major muscles are made of bundles of these fibers Muscles work by to complementary, or opposing actions. These are Contractions – the shortening of a muscle Extension – the stretching of the muscle Muscle contraction is triggered by nerve impulses

Types of Muscles The body contains 3 types of muscles – Smooth Muscle – Skeletal Muscle – Cardiac Muscle

Smooth Muscles Act on the lining of passageways and internal organs Examples: Lining of blood vessels, the digestive tract, lungs, and the bladder. Smooth muscles are under involuntary control

Skeletal Muscles Are attached to bone and cause body movement Skeletal muscles are voluntary muscles Skeletal muscle has a striated or striped appearance Skeletal muscles work together in pairs – Flexors – muscle that closes a joint – Extensors – muscles that open a joint

Cardiac Muscle Type of striated muscle that form the walls of the heart This involuntary muscle is responsible for the contractions of the heart The heart beats about 100,000 times a day to pump blood through the body

Muscular Terms Atrophy – decrease in muscle size and strength. Caused by long periods of physical inactivity Muscle Tone – the natural tension in the fibers of a muscle Physical Activity helps keeps muscles strong, healthy, and toned Practicing good posture strengthens back muscles

Muscles of the Skull Frontalis(forehead) Temporalis(Side of head) Masseter(jaw) Orbicularis oris(eye)

Muscles of the Trunk(Anterior) Pectoralis Major(Chest) Obliques(side of stomach) Abdomen(Stomach)

Muscles of the Trunk(Posterior) Trapezius Rhomboid Latissimus dorsi

Muscles of the Arm Deltoid(shoulder) Bicep(flexor) Tricep(extensor)

Muscles of the Leg Gluteus Maximus(hip extensor) Quadriceps(leg extensor) Hamstrings(leg flexor) Gastrocnemius(foot extensor) Tibialis Anterior(foot flexor)

Problems of the Muscular System Bruise – an area of discolored skin that appears after an injury causes the blood vessels beneath the skin to rupture and leak Muscle Strain – this is when a muscle is stretched or partially torn as a result of overexertion. Tendonitis – inflammation of a tendon, caused by injury, overuse, or natural aging. Includes joint pain and swelling that worsens with activity

Problems with the Muscular System Hernia – when an organ or tissue protrudes through an area of weak muscle. Results from straining to lift a heavy object Muscular Dystrophy – inherited disorder in which muscles are progressively destroyed. There is no cure, exercise can slow the process.