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Crash course: Muscular system. Muscle Groups. Smooth muscle: smooth, involuntary; found in internal organs such as digestive tract, uterus, walls of blood vessels. Skeletal muscle: striated, voluntary, multinucleated; contract rapidly but not for long periods of time.
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Muscle Groups • Smooth muscle: smooth, involuntary; found in internal organs such as digestive tract, uterus, walls of blood vessels. • Skeletal muscle: striated, voluntary, multinucleated; contract rapidly but not for long periods of time. • Cardiac muscle: striated, involuntary; found in the heart; has own control centers.
Muscle Anatomy • Each muscle fiber has a nerve connected to it; a motor neuron makes contact with the fiber’s membrane (sarcolemma). • These motor neurons carry signals from the central nervous system and cause muscle contraction. • Actin and myosin filaments are found in the center of the fiber.
Muscle Contraction • Nerve impulse travels through the motor neuron, stimulating the sarcolemma. • Calcium is released from the sarcoplasmic reticulum; causes myosin binding sites on actin to become exposed. • ATP on tip of myosin hydrolyzes; energy transfer changes the shape of myosin and it binds to actin. • Energy is then released and myosin relaxes into original shape, pulling the actin with it. • New ATP binds to myosin, and process repeats until contraction is complete. • Muscle relaxes when the antagonistic muscle contracts (flexor and extensor). • Calcium has to be actively tranported back into the reticulum to reset the system. • Rigor mortis occurs when no more ATP is available and calcium is not removed from the sarcomere; muscle stays contracted.
Muscle structure and function animation • http://entochem.tamu.edu/MuscleStrucContractswf/index.html
Ooh my little filaments, filaments --Actin and myosin myofibrils:Proteins that are long and dense, long and dense,Making up the structure of the myofibrils. CHORUS:Signal from the brain rides the nerve to the muscle,Where the myosin inside will slide past the actin of theMy-my-my-y-y, woo! Muh-muh-muh-myofibrils. Add a little calcium, calciumTo the cytoplasm near the myofibrils.It will turn troponin on, troponin on,Causing the contraction of the myofibrils. CHORUS Muscles need energy, energy,Most of which is needed by the myofibrils.Myosin burns ATP, ATPFueling the contractions of the myofibrils. CHORUS “Myofibrils” song(My Sharona)