Skeletal Muscle

• What is the primary function of the neuromuscular junction?

  To communicate between nervous and muscular systems
• What happens when a chemical transmitter is released at the neuromuscular junction?

  It diffuses across the neuromuscular cleft

  
• How does the chemical transmitter affect the muscle membrane?

  It increases membrane permeability to sodium

  
• What type of muscle requires stimulation by neurons to contract?

  Skeletal muscle
• How do smooth and cardiac muscles differ from skeletal muscle in terms of contraction?

  They can contract without nerve stimulation
• What occurs if the threshold potential is reached in a muscle cell?

  An action potential occurs, leading to contraction

  
• What are the main functions of muscle tissue?

  • Movement
  • Posture
  • Heat production
• What are the three types of muscle tissue?

  • Skeletal muscle
  • Cardiac muscle
  • Smooth muscle

  
• How does cardiac muscle differ from skeletal muscle in terms of contraction initiation?

  Cardiac muscle contracts spontaneously due to Na+ leak

  
• What connects adjacent cardiac muscle cells?

  Gap junctions
• What is the role of calcium in cardiac muscle contraction?

  Calcium triggers contraction from internal and external sources

  
• What is the primary difference between smooth muscle and skeletal muscle regarding structure?

  Smooth muscle is unstriated and lacks t-tubules
• How does nerve stimulation occur in smooth muscle?

  From autonomic nerves alongside muscle cells
• What initiates action potentials in smooth muscle?

  Calcium ions, not sodium ions

  
• What type of muscle is also called striated muscle?

  Skeletal muscle

  
• What are the characteristics of red muscle fibers?

  Slow twitch, high endurance, numerous mitochondria

  
• What are the characteristics of white muscle fibers?

  Fast twitch, fatigues rapidly, fewer mitochondria

  
• What is the sliding filament theory?

  • Myosin heads interact with actin
  • ATP is used to pull actin past myosin
  • Thick and thin filaments slide past each other
  • Shortening of the sarcomere produces force

  
• What are the steps in crossbridge cycling?

  1. Calcium mobilization exposes actin binding sites
  2. Myosin binds to actin
  3. Power stroke occurs
  4. ATP binds, disconnecting myosin from actin
  5. ATP hydrolysis re-energizes the crossbridge
  6. Calcium is re-uptaken into the SR

  
• What triggers calcium release from the sarcoplasmic reticulum during muscle contraction?

  Depolarization of the muscle cell membrane

  
• What is the role of troponin in muscle contraction?

  It binds calcium and allows cross-bridges to form

  
• What happens to calcium ions after muscle contraction ceases?

  They are pumped back into the sarcoplasmic reticulum

  
• What is the function of T-tubules in muscle cells?

  To conduct impulses to the sarcoplasmic reticulum
• What is the primary role of the sarcoplasmic reticulum in muscle contraction?

  To store and release calcium ions

  
• How does the tropomyosin-troponin-Ca2+ system regulate muscle contraction?

  It blocks myosin binding sites on actin

  
• What occurs when acetylcholine binds to receptor sites on the motor end plate?

  It causes depolarization of the motor end plate

  
• What happens to calcium ions during muscle relaxation?

  They rapidly return to the sarcoplasmic reticulum

  
• What is the final step in the muscle contraction process?

  Tropomyosin returns over active sites on actin