topic 1.2

• Muscle tissue


  • Contractility - ability to actively generate force or create tension/undergo shortening for movements
  • Extensibility - ability to stretch and lengthen beyond normal resting length without damage
  • Elasticity - ability to recoil and return to original shape after contraction/extension
  • Atrophy - decrease in myofibrils/muscle fibre diameter due to lack of physical activity
  • Hypertrophy - increase in myofibrils/muscle fibre diameter due to physical activity
  • Controlled by nerve stimuli - muscles need nerve input to contract
  • Fed by capillaries - capillaries supply oxygen, nutrients and remove waste
• Types of muscle


  • Smooth muscle
  • Cardiac muscle
  • Skeletal muscle
• Smooth muscle


  • Specialised for contracting/changing diameter of lumen in hollow organs
  • Located in internal hollow organs
  • Supplied by autonomic motor neurones
  • Involuntary
  • Single nucleus
• Cardiac muscle


  • Striated muscle fibres
  • Form wall of heart
  • Stimulated by intrinsic conduction system
  • Stimulated by autonomic motor neurones
  • Involuntary
  • Single nucleus
  • Extremely high resistance to fatigue
• Skeletal muscle


  • Specialised for contraction/used for movement
  • Located in muscles e.g. biceps, triceps
  • Composed of striated muscle fibres
  • Supported by connective tissue
  • Attached to bone by tendon
  • Stimulated by somatic motor neurones
  • Voluntary movement/conscious control
  • Cells are multi-nucleated
• Structure of skeletal muscle


  1. Epimysium - outer surrounding layer

  2. Perimysium - surrounds bundles of muscle fibres

  3. Endomysium - surrounds individual muscle fibres

  4. Muscle fibre - composed of myofibrils

  5. Myofibril - composed of actin and myosin filaments

  6. Sarcomere - basic/functional unit of muscle cell
• Origin


  Attachment of muscle tendon to stationary bone
• Insertion


  Attachment of muscle tendon to moveable bone