PPN 8

• What are the primary functions of muscle?

  Movement, posture, glucose storage, heat generation
• How does muscle contribute to blood pressure regulation?

  Muscle generates blood pressure through contraction
• What type of muscle is responsible for voluntary movement?

  Skeletal muscle
• What is the role of cardiac muscle?

  Generation of blood pressure
• What characterizes smooth muscle?

  Contraction of hollow organs
• What are the structural differences between skeletal, cardiac, and smooth muscle?

  • Skeletal Muscle:
  • Striated
  • Voluntary
  • PNS innervation
  • Cardiac Muscle:
  • Striated
  • Involuntary
  • ANS innervation
  • Smooth Muscle:
  • Non-striated
  • Involuntary
  • ANS innervation

  
• What is the appearance of striated muscle due to?

  Order of muscle fibers
• What is a motor unit?

  Motoneurone plus innervated muscle fibers
• What is the typical structure of skeletal muscle fibers?

  Large, rod-like fibers with striations

  
• How are action potentials related to muscle contraction?

  They trigger muscle fibers to contract
• What is the typical number of nuclei in cardiac muscle cells?

  One or two nuclei
• What connects cardiac muscle cells electrically?

  Intercalated disks

  
• What is the appearance of smooth muscle cells?

  Very small cells with no striations
• Why do smooth muscle cells lack striations?

  Actin and myosin are randomly arranged
• What is the process of muscle contraction involving actin and myosin?

  • Cross-bridge cycle:

  1. Myosin heads attach to actin
  2. Power stroke occurs
  3. ATP binds to myosin
  4. Myosin head detaches

  
• What happens to the cross-bridge cycle in the absence of ATP?

  Cross-bridges remain permanently attached
• What is rigor mortis?

  Muscular rigidity after death
• What role do calcium ions play in muscle contraction?

  They stimulate contraction by binding to proteins

  
• What are the key structures involved in muscle contraction and calcium storage?

  • Sarcoplasmic Reticulum (SR): Calcium store
  • T Tubules: Conduct action potentials
  • Myofibrils: Contractile units

  
• How does the sympathetic nervous system affect muscle contraction?

  It increases force per fiber
• How does muscle contraction differ among skeletal, cardiac, and smooth muscle?

  • Skeletal Muscle:
  • Stimulated by motor nerve
  • Contracts only when stimulated
  • Cardiac Muscle:
  • Contracts with each heartbeat
  • Stimulated by action potential
  • Smooth Muscle:
  • Stimulated by depolarization and receptors
• What is the basic functional unit of skeletal muscle?

  The motor unit

  
• What is Henneman’s Size Principle in muscle recruitment?

  Smaller motor units recruited before larger ones

  
• What happens to muscle fibers when a motor unit is stimulated?

  All fibers in the unit contract
• How does the force of contraction relate to the number of activated fibers?

  More activated fibers increase overall force
• What is the effect of sympathetic nervous system on cardiac muscle contraction?

  Increases force of contraction
• How is smooth muscle contraction regulated?

  By receptor stimulation and intracellular calcium
• What are the key take-home messages regarding muscle contraction?

  • Skeletal muscle contracts only when stimulated
  • Cardiac muscle contracts with each heartbeat
  • Smooth muscle contraction varies by tissue
  • Calcium is crucial for contraction