Muscle

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Muscle

• Structure
• and
• Contraction

2
Types of Muscle

• Skeletal or striated (striped) muscle
• Also called voluntary muscle as used for making
  voluntary movements such as walking
• Smooth muscle
• Not striated
• Found in walls of gut, blood vessels and uterus
• Not under voluntary control
• Cardiac
• Similar to striated muscle
• Mononucleate, Smaller, branched cells
• Many more mitochondria than skeletal muscle cells

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Skeletal Muscle
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Smooth Muscle
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Cardiac Muscle
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Striated Muscle

• Muscles are made up of blocks of fibres
• Fibres
• lie parallel to each other
• 0.1 to 0.01 diameter, several cm long
• Long multinucleate cells formed from several
  cells called a syncitium
• Plasma membrane called sarcolemma this is
  deeply folded to form T-tubules (transverse)
• Contain usual organelles esp mitochondria and
  sarcoplasmic reticulum (ER)
• Filled largely with Fibrils alternate bands of
  light and dark

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Structure of Striated Muscle
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Myofibrils

• A bands broad dark band
• I bands lighter band
• Z line thin dark line in I band
• M line down centre of A band
• Sarcomere the part of a fibril between two Z
  lines sarcomeres of adjacent fibrils line up
  exactly

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Myofibrils

• Made up of two types of protein filaments
• Myosin
• fibrous protein with a head and a tail
• Many molecules form thick filaments
• Half heads line up at one end of the filament,
  half at the other, the area where the tails meet
  forms the M line
• Actin
• Globular protein
• Many molecules link up to form long chains
• Two chains twist around each other to form a thin
  filament

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Structure of myofibrils
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Structure of muscle fibres