Muscles L.1

• Muscle cells


  Highly specialized to convert chemical energy (ATP) into kinetic energy
• Types of muscle tissues

  • Smooth
  • Cardiac
  • Skeletal
• Smooth muscle cells


  • Non-striated (no lines)
  • Each have single nucleus
  • Contract involuntarily
  • Found in walls of internal organs (e.g. esophagus peristalsis)
  • Can sustain prolonged contraction without fatigue (e.g. iris constriction)
• Cardiac muscle cells


  • Striated, tubular, and branched
  • Each have single nucleus
  • Contract involuntarily
  • Found in walls of heart
• Skeletal muscle cells


  • Striated and tubular
  • Each have many nuclei
  • Contract voluntarily
  • Usually attached to bones of skeleton
• Which muscle type is which?

  • Smooth
  • Cardiac
  • Skeletal
• Skeletal muscle function


  • Support - contraction of muscles opposes force of gravity
  • Movement - allows for movement of bones (i.e., arms and legs) as well as eyes and face
  • Maintain body temperature - ATP breakdown releases heat spread throughout body
  • Protection - pads bones and cushions organs
  • Stabilize joints - tendons help hold bones to joints
• Cooperation of skeletal muscles


  1. Muscles contract, they shorten and pull (NOT push)

  2. Contraction = work; relaxation = no work

  3. Muscles are found in pairs - one action always has an opposing action (e.g. bicep flex = bent arm; tricep flex = straight arm)
• Skeletal muscle structure


  • Muscles - largest unit; attached to bone by tendons
  • Muscle fibres - organized into larger bundles; up to 20 cm long
  • Myofibrils - thousands of cylindrical subunits
  • Myofilaments - protein structures responsible for muscle contraction; two types (actin, myosin)