Physiology

• What are the functions of skeletal muscle?

  Posture, movement, respiratory movements, heat, metabolism
• What type of muscle is smooth muscle?

  Involuntary and non-striated
• What type of muscle is cardiac muscle?

  Involuntary and striated
• What type of muscle is skeletal muscle?

  Voluntary and non-striated
• How can striation in skeletal muscle be visualized?

  Under a light microscope as alternating dark and light bands
• What is the difference between neurogenic and myogenic muscle types?

  Skeletal is neurogenic; cardiac is myogenic
• What is present at the neuromuscular junction?

  Neuromuscular junctions are present in skeletal muscle
• Where does calcium come from in cardiac muscle contraction?

  From extracellular fluid and sarcoplasmic reticulum
• Where does calcium come from in skeletal muscle contraction?

  Only from the sarcoplasmic reticulum
• How are skeletal muscles arranged?

  Into motor units with muscle fibers innervated by one alpha motor neuron
• What initiates contraction in skeletal muscles?

  Stimulation of alpha motor neurons
• What neurotransmitter is involved in skeletal muscle contraction?

  Acetylcholine (Ach)
• What is the relationship between precision and muscle fibers per motor unit?

  Less muscle fibers per motor unit for precision
• What is the relationship between power and muscle fibers per motor unit?

  More muscle fibers per motor unit for power
• What is the structure of skeletal muscle from largest to smallest?

  • Muscle
  • Muscle fiber
  • Myofibril
  • Sarcomere (actin + myosin)
• What is the functional unit of skeletal muscle?

  The sarcomere
• What are the components of a sarcomere?

  Actin (thin) and myosin (thick)
• What is the A-band in a sarcomere?

  the dark band of the sarcomere that generates force and movement
• What is the H-zone in a sarcomere?

  Lighter area in the middle of A-band
• What are the four zones of a sarcomere?

  1. band, H-zone, M-line, I-band
• What is the M-line in a sarcomere?

  Vertical line down the middle of A-band
• What is the I-band in a sarcomere?

  Thin filaments that don’t project in A-band
• How is muscle tension produced?

  By sliding of actin filaments on myosin filaments
• What is ATP needed for in muscle contraction?

  Contraction and relaxation processes
• What is the sequence of events in muscle contraction?

  Ach release, action potential, Ca2+ release, cross bridge formation
• How does the time for action potential compare to muscle twitch?

  Time for action potential is less than muscle twitch
• What factors determine muscle tension?

  Number of fibers contracting and tension developed
• What happens if multiple action potentials occur in muscle?

  Muscle won’t relax and tension summates
• What is tetanus in muscle contraction?

  Maximum sustained contraction from rapid stimulation
• What is a single contraction of skeletal muscle called?

  A twitch
• What transmits skeletal muscle tension to bone?

  Stretching of tendons
• Why does tetanus not occur in cardiac muscle?

  Due to the refractory period
• What are the two types of skeletal muscle contraction?

  • Isotonic contraction: tension constant, muscle length changes
  • Isometric contraction: tension develops, muscle length constant
• When is maximal contraction achieved in skeletal muscle?

  When muscle is at optimal length
• How does lifting weights affect muscle contraction?

  Slower lifting allows heavier weights to be lifted
• What happens to the velocity of muscle shortening as load increases?

  Velocity of shortening decreases
• What are the pathways that supply ATP to muscle fibers?

  • Creatine phosphate -> ADP
  • Oxidative phosphorylation
  • Glycolysis
• What type of activities do Type I muscle fibers support?

  Aerobic, low work activities like walking
• What type of activities do Type IIa muscle fibers support?

  Aerobic and anaerobic, moderate activities like jogging
• What type of activities do Type IIx muscle fibers support?

  Anaerobic, short-term high intensity activities like jumping