Muscles and Muscular Contraction

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Muscles and Muscular Contraction
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3 types of muscle cells

• Smooth muscle internal organ walls, blood
  vessels (enables dilation and contraction)
• Sheets of cells, all acting in concert
• Many work together to squeeze
• Involuntary muscle
• Spindle shaped

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• Cardiac Muscle
• Only found in heart
• Striated
• Involuntary
• Syncytium group of cells contract together,
  acting as a group

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• Skeletal Muscle
• Voluntary muscle
• Multinucleated
• Striated

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Skeletal cont

• Structure
• Muscle?Fasicle?
• Myofiber (cell)? Myofibril?Myofilaments
• Many myofibers connected lengthwise through
  entire fiber
• Many mitochondria
• Many nuclei (why? The multiple nuclei arise from
  the fact that each muscle fiber develops from the
  fusion of many cells (called myoblasts).

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Skeletal cont

• Sarcomere (small part of myofibril)
• Made up of thin (Actin) and thick (Myosin)
  filaments

You dont need to know these different zones!
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Contraction Sliding Filament Theory

• When muscle contracts its shortens. When muscle
  relaxes it DOES NOT lengthen beyond relaxed state
• Actin and Myosin slide across one another (they
  do not shorten or lengthen)
• Myosin head binds actin and pulls it, causing
  sliding. Requires help of Calcium and _______.

ATP
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Tendons

• Connect Muscle to bones, helps joints bend when
  muscle fibers contract, pulls on bone