chapter 9: muscles and muscle tissue. 2 governor arnold schwarzenegger
TRANSCRIPT
Chapter 9:Muscles and Muscle
Tissue
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Cardiac Muscle• forms the
heart• used to pump
blood through circulatory system
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Smooth Muscle• lines gut and blood
vessels• controls diameter
of these tubes and in gut helps to propel the digested food
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Property SkeletalMuscle
CardiacMuscle
SmoothMuscle
Striations? Yes Yes No
Nuclei per Cell Many Single Single
Cells Connected byIntercalated
Discs or Gap Junctions?
No Yes Yes
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Relative Speed of Contraction
Fast Intermediate Slow
Voluntary Control?
Yes No No
Control of Contraction
Nerves
Beats spontaneously
but modulated by nerves
NervesHormones
Stretch
Property SkeletalMuscle
CardiacMuscle
SmoothMuscle
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Muscle cells• Large, long cells called FIBERS • Contain two types of proteins--actin
and myosin• Excitable (irritable), contractile,
extensible, and elastic • Myo-, mys, or Sarco code for muscle
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Skeletal Muscle Anatomy
•Rich blood supply to center of muscle, branch to capillaries sheathing cells
•Rich nerve supply, branching into each muscle, ending one branch to each muscle fiber
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Structure of Skeletal Muscle
• Cigar shaped, multinucleate cells • Packed with myofilaments made
of actin and myosin creating visible bands (striations)
• Varied length, may be over a foot long
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Structure cont.• Surrounded by dense, fibrous
Connective tissue (CT) sheaths• Endomysium around each fiber • Perimysium around bundles of
fibers (fascicles) • Epimysium around all fascicles
14Figure 6.1 Connective tissue wrappings of skeletal muscle.
© 2000 The Benjamin/Cummings Publishing Company
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Microscopic structure• Muscle fibers filled with Sarcoplasm
– Glycogen and myoglobin
• Nuclei pushed to the edge of sarcolemma by long protein strands that run length of the cell, myofibrils
• Composed of contractile units, sarcomeres, made of myofilaments
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Figure 6.3 Anatomy of a skeletal muscle cell (fiber). (a) A portion of a muscle fiber. One myofibril has been extended. (b) Enlarged view of a myofibril showing its banding pattern. (c) Enlarged view of one sarcomere (contractile unit) of a myofibril. (d) Structure of the thick and thin myofilaments found in the sarcomeres.
© 2000 The Benjamin/Cummings Publishing Company
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Myofilaments• Two types--actin and myosin -Filaments are clusters of actin and myosin • Actin forms thin filaments • Myosin forms thick filaments
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Sarcomere structure
• Alternating dark and light bands • Lateral dark bands--A-band • End in light I-bands, with Z-line in
center marking joint with next sarcomere on each side
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Muscle Contraction
• Sarcomere - basic unit of muscle contraction
• Skeletal and cardiac muscle are striated
• The striations are caused by alignment of bands: the most prominent are the A and I bands and the Z line
• The unit between 2 Z lines is called the sarcomere
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Muscle Contraction-Sarcomere
• In the A band the 2 proteins overlap • The I band contains only the actin protein
• When muscle contracts the sarcomere shortens and
the Z lines move closer together
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Muscle Contraction-relaxed state
• When Muscle Contracts Protein Filaments Slide Together
• Thin filaments: actin, attached to Z line, found in both A and I bands
• Thick filaments: myosin, found in A band • Relaxed state:
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Muscle Contraction-Contracted state
• When muscle contracts the actin filaments slide into the A band, overlapping with myosin
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Muscle Contraction-Contracted state
• Notice what happens when muscle contracts: – a) the Z lines move closer together – b) the I band becomes shorter – c) the A band stays at the same length
• This is called the "sliding filament" model of muscle contraction
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Muscle Contraction-Crossbridge
• The filaments slide together because myosin attaches to actin and pulls on it
• myosin head(H) attaches to actin filament (A), forming a crossbridge
• After the crossbridge is formed the myosin head bends, pulling on the actin filaments and causing them to slide: