Muscles

• What are the three types of muscle tissue?

  Involuntary, cardiac, and skeletal muscle
• Where is smooth muscle found?

  In the walls of tubular structures
• What shape are smooth muscle cells?

  Spindle-shaped and mononucleated
• How is smooth muscle controlled?

  By the autonomic nervous system
• How does smooth muscle contract?

  Slowly and regularly in different directions
• What is the appearance of smooth muscle fibers?

  Non-striated
• What type of muscle is cardiac muscle?

  A specialized striated muscle
• What do intercalated discs in cardiac muscle do?

  Allow free diffusion of calcium ions
• How does cardiac muscle contract?

  Simultaneously across the heart chambers
• What is the contraction speed of cardiac muscle?

  Intermediate speed and length
• Where is skeletal muscle found?

  At the joints in the skeleton
• How is skeletal muscle controlled?

  By the somatic nervous system
• What is the contraction speed of skeletal muscle?

  Rapid but short
• What is the arrangement of skeletal muscle fibers?

  Regularly arranged and heavily striated
• What surrounds each skeletal muscle fiber?

  The sarcolemma
• What does the sarcoplasm of skeletal muscle contain?

  Many mitochondria and an extensive sarcoplasmic reticulum
• What do transverse tubules do in skeletal muscle?

  Spread electrical impulses throughout the sarcoplasm
• What are myofibrils?

  The contractile unit of skeletal muscle
• What types of filaments do myofibrils contain?

  Actin and myosin filaments
• What forms the light band in myofibrils?

  Thin filaments (actin) aligned together
• What is the Z-line in myofibrils?

  The structure holding thin filaments together
• What is the H zone in myofibrils?

  The area where thick and thin filaments do not overlap
• What is a sarcomere?

  The functional unit of muscle between Z-lines
• What surrounds the sarcomere?

  The sarcoplasmic reticulum
• What is the role of the neuromuscular junction?

  To propagate action potentials to the motor unit
• What happens when action potentials reach the end of the axon?

  Calcium ion channels open, allowing calcium influx
• What does acetylcholine do at the neuromuscular junction?

  It binds to receptors in the sarcolemma
• What is the result of acetylcholine binding to receptors?

  Opens sodium ion channels, depolarizing the sarcolemma
• What happens after the sarcolemma is depolarized?

  A wave of depolarization spreads along the sarcolemma
• What occurs during muscle contraction according to the sliding filament hypothesis?

  The light band and H-zone get shorter
• What triggers the release of calcium ions during contraction?

  The action potential reaching the sarcoplasmic reticulum
• What does calcium bind to during contraction?

  Troponin
• What happens when calcium binds to troponin?

  Tropomyosin is pulled from binding sites on actin
• What forms when myosin heads bind to actin?

  A cross-bridge between the filaments
• What occurs during the power stroke?

  Myosin pulls actin past it while hydrolyzing ATP
• What happens after the power stroke?

  A new ATP molecule attaches to myosin head
• What is the role of creatine phosphate during muscle contraction?

  Acts as a reserve of phosphate groups for ATP regeneration
• What happens to calcium ions after muscle contraction?

  They are pumped back into the sarcoplasmic reticulum
• What is required for myofibril contractions?

  A large volume of ATP
• How is ATP regenerated during muscle activity?

  Through aerobic and anaerobic respiration