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Skeletal Muscle
- Usually attached to bones
- Voluntary
- Striated (filaments in bands)
- Multinucleated
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Cardiac Muscle
- Wall of heart
- Involuntary
- Striated and branched (intercalated disks)
- Single nucleus
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Smooth Muscle
- Walls of most viscera, blood vessels and skin
- Involuntary
- Not striated
- One centrally located nucleus
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Compared to skeletal muscle fibers, smooth muscle fibers are:
- Shorter
- Single, centrally located nucleus
- Elongated with tapering ends
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Visceral Smooth Muscle
- Single-unit smooth muscle
- Sheets of muscle fibers
- Fibers held together by gap junctions
- Exhibit rhythmicity
- Exhibit peristalsis
- Walls of most hollow organs
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Multi-unit Smooth Muscle
- Less organized
- Function as separate units (Fibers function separately)
- Iris of eye
- Walls of blood vessels
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Cardiac Muscle
- Located only in the heart
- Muscle fibers joined together by intercalated discs
- Fibers branch
- Network of fibers contracts as a unit
- Self-exciting and rhythmic
- Longer refractory period than skeletal muscle
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Tissues of the muscular system:
- Skeletal muscle tissue
- Nervous tissue
- Blood
- Connective tissues
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Types of dense, white, fibrous connective tissue found in skeletal muscles throughout body:
- Fascia—layered; covers all muscles
- Tendons—cordlike; connects muscle to bone
- Aponeuroses—sheetlike; connects muscle to muscle
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Connective tissues found covering individual muscles:
- Epimysium
- Perimysium
- Endomysium
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Muscle Structure:
- Fascicles
- Muscle fiber (muscle cell)
- Myofibrils
- Thin and thick myofilaments
- Actin (thin) and myosin (thick) proteins
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Parts of a sarcomere:
- I band (actin-thin)
- A band (myosin-thick and actin-thin)
- H zone (myosin-thick)
- Z line (actin disc)
- M line (myosin)
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Thick myofilaments
- Composed of myosin protein
- Form the cross-bridges
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Thin myofilaments
- Composed of actin protein
- Associated with troponin and tropomyosin proteins