skeletal muscle

• What are the three types of muscles?

  Smooth, cardiac, and skeletal
• Where are smooth muscles found?

  In internal organs and blood vessels
• What type of muscle makes up the heart?

  Cardiac muscle
• How does skeletal muscle work?

  In antagonistic pairs attached to bone
• What are muscle fibers made up of?

  Myofibrils
• What are myofibrils made of?

  Thin (actin) and thick (myosin) filaments
• What are actin chains wrapped with?

  One tropomyosin molecule
• What does Myosin consist of?

  Two myosin chains wrapped and bundled
• What repeating units make up myofibrils?

  Sarcomeres
• What is the lighter area of sarcomeres made of only thin filaments called?

  I bands
• What are the darker areas of sarcomeres made of both thick and thin filaments called?

  A band
• What is the slightly lighter area within the A band that is made of only myosin called?

  H zone
• What is found at the center of each I band?

  The Z line
• What is found at the center of each A band?

  The M line
• What happens to sarcomere sections during muscle contraction according to the sliding filament mechanism?

  Thick and thin sections contract
• What releases calcium ions when a muscle fiber becomes depolarized?

  Sarcoplasmic reticulum
• What happens when calcium ions are released?

  Tropomyosin moves away from actin binding sites
• What is formed when myosin heads attach to actin binding sites?

  Actomyosin bridge
• What causes the myosin head to detach from actin?

  ATP binds to myosin head
• What is released from the myosin head during the power stroke?

  ADP and Pi
• What happens to ATP after it binds to the myosin head?

  It hydrolyses and returns to start
• Which areas of the sarcomere become narrower during muscle contraction?

  I band and H zone
• What happens to the Z lines during muscle contraction?

  They move closer together
• Which band stays the same width during muscle contraction?

  The A band
• How many ATP sources do muscle fibers provide for muscle contraction?

  Three
• When does aerobic respiration take place in muscles?

  When ATP demand matches glucose/oxygen
• When does anaerobic respiration take place in muscles?

  When ATP demand exceeds glucose/oxygen
• What does phosphocreatine allow?

  Rapid conversion to ATP from ADP
• What primarily determines which ATP sources are used in muscle contraction?

  The type of skeletal muscle fiber
• Where are fast twitch muscle fibers typically found?

  Arms and legs
• What type of contractions do fast twitch muscle fibers create?

  Fast, powerful contractions
• What are the primary sources of ATP for fast twitch muscle fibers?

  Anaerobic respiration and phosphocreatine
• What is the organelle composition of fast twitch muscle fibers?

  Lots of phosphocreatine, few mitochondria
• Where are slow twitch muscle fibers typically found?

  Back and calves
• What type of contractions do slow twitch muscle fibers create?

  Slow, weak contractions
• What are the primary sources of ATP for slow twitch muscle fibers?

  Aerobic respiration and phosphocreatine
• What is the organelle composition of slow twitch muscle fibers?

  Little phosphocreatine, many mitochondria
• Why do slow twitch fibers rely less on anaerobic respiration?

  Many mitochondria reduce the need
• Why is less lactate produced in slow twitch fibers?

  Due to more aerobic respiration
• What does less lactate limit in slow twitch fibers?

  Aerobic respiration