the muscular system - denver school of the...
TRANSCRIPT
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The Muscular System
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The Muscular System
Slide 6.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Muscles are responsible for all types of body movement – they contract or shorten and are the machine of the body
• Three basic muscle types are found in the body • Skeletal muscle
• Cardiac muscle
• Smooth muscle
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Characteristics of Muscles
Slide 6.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Muscle cells are elongated (muscle cell = muscle fiber)
• Contraction of muscles is due to the movement of microfilaments
• All muscles share some terminology • Prefix myo refers to muscle
• Prefix mys refers to muscle
• Prefix sarco refers to flesh
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Skeletal Muscle Characteristics
Slide 6.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Most are attached by tendons to bones
• Cells are multinucleate
• Striated – have visible banding
• Voluntary – subject to conscious control
• Cells are surrounded and bundled by connective tissue = great force, but tires easily
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Connective Tissue Wrappings of Skeletal Muscle
Slide 6.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Endomysium – around single muscle fiber
• Perimysium – around a fascicle (bundle) of fibers Figure 6.1
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Connective Tissue Wrappings of Skeletal Muscle
Slide 6.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Epimysium – covers the entire skeletal muscle
• Fascia – on the outside of the epimysium
Figure 6.1
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Skeletal Muscle Attachments
Slide 6.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Epimysium blends into a connective tissue attachment • Tendon – cord-like structure • Aponeuroses – sheet-like structure
• Sites of muscle attachment • Bones • Cartilages • Connective tissue coverings
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Smooth Muscle Characteristics
Slide 6.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Has no striations • Spindle-shaped
cells • Single nucleus • Involuntary – no
conscious control • Found mainly in
the walls of hollow organs
• Slow, sustained and tireless Figure 6.2a
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Cardiac Muscle Characteristics
Slide 6.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Has striations • Usually has a
single nucleus • Joined to another
muscle cell at an intercalated disc
• Involuntary • Found only in the
heart • Steady pace! Figure 6.2b
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Function of Muscles
Slide 6.8 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Produce movement
• Maintain posture
• Stabilize joints
• Generate heat
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Microscopic Anatomy of Skeletal Muscle
Slide 6.11a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Organization of the sarcomere • Thick filaments = myosin filaments • Thin Filaments are Actin
Figure 6.3c
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Microscopic Anatomy of Skeletal Muscle
Slide 6.12a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Myosin filaments have heads (extensions, or cross bridges)
• Myosin and actin overlap somewhat
Figure 6.3d
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The Sliding Filament Theory of Muscle Contraction
Slide 6.17b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• This continued action causes a sliding of the myosin along the actin
• The result is that the muscle is shortened (contracted)
Figure 6.7
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Contraction of a Skeletal Muscle
Slide 6.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Muscle fiber contraction is “all or none” • Within a skeletal muscle, not all fibers
may be stimulated during the same interval
• Different combinations of muscle fiber contractions may give differing responses
• Graded responses – different degrees of skeletal muscle shortening, rapid stimulus = constant contraction or tetanus
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Muscle Fatigue and Oxygen Debt
Slide 6.27 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• When a muscle is fatigued, it is unable to contract
• The common reason for muscle fatigue is oxygen debt • Oxygen must be “repaid” to tissue to remove
oxygen debt • Oxygen is required to get rid of accumulated
lactic acid • Increasing acidity (from lactic acid) and lack
of ATP causes the muscle to contract less
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Muscle Tone
Slide 6.29 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Some fibers are contracted even in a relaxed muscle
• Different fibers contract at different times to provide muscle tone
• The process of stimulating various fibers is under involuntary control
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Muscles and Body Movements
Slide 6.30a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Movement is attained due to a muscle moving an attached bone
Figure 6.12
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Muscles and Body Movements
Slide 6.30b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Muscles are attached to at least two points • Origin –
attachment to a moveable bone
• Insertion – attachment to an immovable bone
Figure 6.12
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Types of Muscles
Slide 6.35 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Prime mover – muscle with the major responsibility for a certain movement
• Antagonist – muscle that opposes or reverses a prime mover
• Synergist – muscle that aids a prime mover in a movement and helps prevent rotation