anatomy & physiology i unit 8: muscular system review
TRANSCRIPT
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Anatomy & Physiology I
Unit 8: Muscular System Review
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Did you know that ?
- more than 50% of body weight is muscle !
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Three types of muscle
Skeletal Cardiac Smooth
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Classification of muscle
Voluntary Involuntary
Limbs Heart Viscera
Striated Non-striated
Skeletal Cardiac Smooth
Note: Control, Location and Structure
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Skeletal muscle
• Large muscles• Maintain posture • Facilitate locomotion• Move jointed bones• Found in antagonistic pairs• Joined to bones by tendons
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Structure of skeletal muscle
• Each cell (fibre) is long and cylindrical• Muscle fibres are multi-nucleated• Typically 50-60mm in diameter, and up
to 10cm long• The contractile elements of
skeletal muscle cells aremyofibrils
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Skeletal muscle - Summary
• Voluntary movement of skeletal parts
• Spans joints and attached to skeleton
• Multi-nucleated, striated, cylindrical fibres
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Cardiac muscle
• Main muscle of heart• Pumping mass of heart• Critical in humans• Heart muscle cells
behave as one unit• Heart always contracts
to it’s full extent
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Structure of cardiac muscle
• Cardiac muscle cells (fibres) are short, branched and interconnected
• Cells are striated & multi-nucleated• Adjacent cardiac cells joined via electrical
synapses (gap junctions)• These gap junctions appear as dark lines when
viewed under LM, and are called intercalated discs
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Cardiac muscle - Summary
• Found in the heart• Involuntary rhythmic
contraction• Branched, striated
fibre with single nucleus and intercalated discs
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Smooth muscle
• Lines walls of viscera
• Found in longitudinal or circular arrangement
• Alternate contraction of circular & longitudinal muscle in the intestine leads to peristalsis
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Structure of smooth muscle
• Spindle shaped uni-nucleated cells• Striations not observed • Actin and myosin filaments are present• Ratio of thin-to-thick filaments is 16:1 (in
striated muscle this is 2:1)• Myosin filaments are attached to
dense bodies at the end of eachcell
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Smooth muscle - Summary
• Found in walls of hollow internal organs
• Involuntary movement of internal organs
• Elongated, spindle shaped fibre with single nucleus
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Muscle Control
Type of muscle
Nervouscontrol
Type of control
Example
SkeletalSkeletal Controlled by CNS
Voluntary Lifting a glass
Cardiac Regulated by ANS
Involuntary Heart beating
Smooth Controlled by ANS
Involuntary Peristalsis