Muscles

• What does it mean for muscles to occur in antagonistic pairs?

  One muscle contracts while the other relaxes
• How can muscle movement be triggered?

  Automatically or through conscious thought
• What is the structure of skeletal muscle that is focused on?

  Myofibril
• What is the cytoplasm of muscle cells called?

  Sarcoplasm
• Why do myofibrils have a high number of mitochondria?

  ATP is essential for muscle contraction
• What two key proteins make up myofibrils?

  Myosin and actin
• How are myosin and actin arranged in a sarcomere?

  Actin is thin, myosin is thick
• What happens to the I band during muscle contraction?

  The I band decreases in width
• What is the H zone in a sarcomere?

  Area with only myosin present
• What initiates muscle contraction according to the sliding filament theory?

  Action potential reaching the muscle
• What role do calcium ions play in muscle contraction?

  They bind to tropomyosin, exposing binding sites
• What is the term for the connection formed between myosin and actin?

  Cross bridge
• What happens to ADP and Pi during muscle contraction?

  They are released when myosin pulls actin
• What causes the myosin head to detach from actin?

  Binding of a new ATP molecule
• What enzyme hydrolyzes ATP attached to the myosin head?

  ATPase
• What happens to the A band during muscle contraction?

  The A band remains constant in width
• What is the role of phosphocreatine in muscle contraction?

  It helps regenerate ATP from ADP
• What are the differences between slow twitch and fast twitch muscle fibers?

  Slow Twitch Fibers:

  • Large stores of myoglobin
  • Rich blood supply
  • Higher proportion of mitochondria
  • Contract slower, good for endurance

  
  

  Fast Twitch Fibers:

  • Thicker muscles with more myosin
  • Large stores of glycogen and phosphocreatine
  • High concentration of anaerobic respiration enzymes
  • Contract faster, good for short bursts
• What happens to muscle fibers with endurance training?

  Higher proportion of slow twitch fibers develops
• Why do fast twitch muscles fatigue quickly?

  They rely on anaerobic respiration
• What is the significance of ATP in muscle contraction?

  ATP is essential for muscle contraction
• How do the I band and H zone change during muscle contraction?

  Both decrease in width during contraction
• What remains unchanged during muscle contraction?

  The width of the A band
• What happens to the Z lines during muscle contraction?

  The Z lines move closer together