Developmental Aspects Cardiac and skeletal muscle become amitotic but can

Developmental aspects cardiac and skeletal muscle

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Developmental Aspects Cardiac and skeletal muscle become amitotic, but can lengthen and thicken in growing child Myoblast-like skeletal muscle satellite cells have limited regenerative ability Cardiomyocytes can divide at modest rate, but injured heart muscle is mostly replaced by connective tissue Smooth muscle regenerates throughout life
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Developmental Aspects Muscular development reflects neuromuscular coordination Development occurs head to toe, and proximal to distal Peak natural neural control occurs by midadolescence Athletics and training can improve neuromuscular control
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Developmental Aspects Female skeletal muscle makes up 36% of body mass Male skeletal muscle makes up 42% of body mass, primarily due to testosterone Body strength per unit muscle mass is the same in both sexes
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Developmental Aspects With age, connective tissue increases and muscle fibers decrease By age 30, loss of muscle mass ( sarcopenia ) begins Regular exercise reverses sarcopenia Atherosclerosis may block distal arteries, leading to intermittent claudication and severe pain in leg muscles
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Myoblasts Fuse to Form a Multinucleate Skeletal Muscle Fiber Figure 9.27 Myoblasts fuse to form a multinucleate skeletal muscle fiber. Mature skeletal muscle fiber Embryonic mesoderm cells called myoblasts undergo cell division (to increase number) and enlarge. Several myoblasts fuse together to form a myotube. Myotube matures into skeletal muscle fiber. Embryonic mesoderm cells Satellite cell Myoblas ts Myotube (immature multinucleat e muscle fiber) 1 2 3
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Muscular Dystrophy Group of inherited muscle-destroying diseases; generally appear in childhood Muscles enlarge due to fat and connective tissue deposits Muscle fibers atrophy and degenerate
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Muscular Dystrophy Duchenne muscular dystrophy (DMD): Most common and severe type Inherited, sex-linked, carried by females and expressed in males (1/3500) as lack of dystrophin Cytoplasmic protein that stabilizes sarcolemma Fragile sarcolemma tears Ca 2+ entry damaged contractile fibers inflammatory cells muscle mass drops Victims become clumsy and fall frequently; usually die of respiratory failure in 20s
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Muscular Dystrophy No cure Prednisone improves muscle strength and function Myoblast transfer therapy is disappointing Coaxing dystrophic muscles to produce more utrophin (protein similar to dystrophin) is successful in mice Viral gene therapy and infusion of stem cells with correct dystrophin genes show promise
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A Boy with Duchenne Muscular Dystrophy (DMD) Figure 9.4 A boy with Duchenne muscular dystrophy (DMD).
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Chapter Ten Dr. Robinson Athens Technical College Fall 2016
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Actions and Interactions of Skeletal Muscles Functional Groups Prime mover ( agonist ) Major responsibility for producing specific movement Antagonist Opposes or reverses particular movement Prime mover and antagonist on opposite sides of joint across which they act
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Skeletal Muscles: Functional Groups Synergist helps prime movers Adds extra force to same movement
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