Muscular System

• Functions of Muscular System

  • Movement
  • Maintain posture
  • Respiration
  • Production of body heat
  • Communication
  • Heart beat
  • Contraction of organs and vessels
• Types of Muscles

  • Skeletal
  • Cardiac
  • Smooth
• Abilities of Skeletal Muscles

  • Contractility: ability to shorten
  • Excitability: respond to stimulus
  • Extensibility: can stretch
  • Elasticity: recoil
• Skeletal Muscle Characteristics

  • Makes up 40% of body weight
  • Named because attached to bones (skeleton)
  • Many nuclei per cell (near periphery)
  • Striated
  • Longest of muscle types
• Skeletal Muscle Structures-Connective Tissue Coverings

  • Epimysium
  • Muscle fascicles
  • Perimysium
  • Muscle fiber
  • Endomysium
• Skeletal Muscle Structures-Connective Tissue Coverings

  Epimysium: connective tissue that surrounds entire skeletal muscle (outside)
• Skeletal Muscle Structures-Connective Tissue Coverings

  Muscle fascicles: bundle of muscle fibers
• Skeletal Muscle Structures-Connective Tissue Coverings

  Perimysium: connective tissue around each muscle fasciculus
• Skeletal Muscle Structures-Connective Tissue Coverings

  Muscle fiber: skeletal muscle cells; many nuclei
• Skeletal Muscle Structures-Connective Tissue Coverings

  Endomysium: connective tissue that surrounds each muscle fiber
• Skeletal Muscle Structures-Muscle Fiber Structure

  • Myofibril
  • Myofilament
  • Sarcoplasm
  • Sarcolemma
  • T-tubules (transverse tubules)
  • Sarcoplasmic reticulum
• Skeletal Muscle Structures-Muscle Fiber Structure

  Myofibril: thread-like proteins that make up muscle fibers
• Skeletal Muscle Structures-Muscle Fiber Structure

  Myofilament: proteins that make up myofibrils (ex. actin and myosin)
• Skeletal Muscle Structures-Muscle Fiber Structure

  Sarcoplasm: cytoplasm of muscle fiber (cell)
• Skeletal Muscle Structures-Muscle Fiber Structure

  Sarcolemma: cell membrane; contains T-tubules
• Skeletal Muscle Structures-Muscle Fiber Structure


  T-tubules (transverse tubules): wrap around sarcomeres at A band; associated with sarcoplasmic reticulum
• Skeletal Muscle Structures-Muscle Fiber Structure

  Sarcoplasmic reticulum: type of SER; surrounds myosin; stores and releases Ca2+
• Skeletal Muscle Structures-Actin and Myosin Myofilaments

  Actin: thin myofilament; resemble 2 strands of pearls
• Skeletal Muscle Structures-Actin and Myosin Myofilaments

  Myosin: thick myofilament; resemble golf clubs
• Skeletal Muscle Structures-Actin and Myosin Myofilaments

  Troponin: attachment site on actin for Ca2+
• Skeletal Muscle Structures-Actin and Myosin Myofilaments

  Tropomyosin: filament on grooves of actin; attachment site on actin for myosin
• Skeletal Muscle Structures-Actin and Myosin Myofilaments

  • Actin
  • Myosin
  • Troponin
  • Tropomyosin
• Skeletal Muscle Structures-Sarcomeres

  • Sarcomere
  • Z disk
  • H zone
  • I band
  • A band
  • M line
• Skeletal Muscle Structures-Sarcomeres

  Sarcomere: contractile unit; contains actin and myosin
• Skeletal Muscle Structures-Sarcomeres

  Z disk: protein fibers that form attachment site for actin
• Skeletal Muscle Structures-Sarcomeres

  H zone: center of sarcomere; contains only myosin
• Skeletal Muscle Structures-Sarcomeres

  I band: contains only actin
• Skeletal Muscle Structures-Sarcomeres

  A band: where actin and myosin; overlap
• Skeletal Muscle Structures-Sarcomeres

  M line: where myosin are anchored
• Resting Membrane Potential

  Outside cell

  • Sodium
  • Positive charge
  • Sodium channels are closed
• Resting Membrane Potential

  Inside cell

  • Potassium
  • Negative charge
  • Some Potassium channels are open
• Depolarization

  • changes in charges
  • inside become more positive and outside more negative
  • sodium channels are open
• Repolarization

  • sodium channels close
  • change back to resting potential
• Nerve Supply

  • Motor neuron
  • Neuromuscular junction (synapse)
  • Presynaptic terminal
  • Postsynaptic membrane
  • Synaptic cleft
  • Synaptic vesicle
  • Neurotransmitter
  • Motor unit
• Nerve Supply

  Motor neuron: nerve cells that carry action potentials to muscle fibers
• Nerve Supply

  Neuromuscular junction (synapse): where nerve cell and muscle fiber meet
• Nerve Supply

  Presynaptic terminal: end of nerve cell (axon)
• Nerve Supply

  Postsynaptic membrane: muscle fiber membrane
• Nerve Supply

  Synaptic cleft: space between presynaptic terminal and postsynaptic membrane
• Nerve Supply

  Synaptic vesicle: in presynaptic terminal; store and release neurotransmitters