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Muscle Tissue and Contraction - Anatomy & Physiology

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  • What are the three types of muscle tissue?
    Skeletal, Cardiac, and Smooth muscle.
  • What prefixes are commonly used in muscle terminology?
    Myo, mys, and sarco.
  • Key characteristics of skeletal muscle tissue?
    Long, cylindrical fibers with striations; voluntary control; contracts rapidly and powerfully.
  • Key characteristics of cardiac muscle tissue?
    Found only in heart; striated; involuntary; contracts at steady rate due to pacemaker.
  • Key characteristics of smooth muscle tissue?
    Found in walls of hollow organs; nonstriated; involuntary control.
  • Four main characteristics shared by all muscle tissue?
    Excitability, Contractility, Extensibility, and Elasticity.
  • Four important functions of muscle tissue?
    Produce movement, maintain posture, stabilize joints, and generate heat.
  • What connective tissue sheaths surround skeletal muscle from external to internal?
    Epimysium surrounds entire muscle, Perimysium surrounds fascicles, Endomysium surrounds individual muscle fibers.
  • Difference between origin and insertion in muscle attachments?
    Origin attaches to immovable bone; insertion attaches to movable bone.
  • What is a sarcomere?
    Smallest contractile unit of muscle fiber, between two Z discs.
  • What proteins compose thick and thin filaments in muscle fibers?
    Thick filaments are made of myosin; thin filaments are made of actin with regulatory proteins troponin and tropomyosin.
  • Role of titin in muscle fibers?
    Elastic filament that holds thick filaments in place and helps recoil after stretch.
  • What causes Duchenne muscular dystrophy (DMD)?
    Defective gene for dystrophin, leading to fragile sarcolemma and progressive muscle weakness.
  • Function of sarcoplasmic reticulum (SR) in muscle fibers?
    Stores and releases Ca2+ to regulate muscle contraction.
  • What are T tubules and their function?
    Invaginations of sarcolemma that conduct electrical impulses deep into muscle fiber.
  • Explain the sliding filament model of muscle contraction.
    Thin filaments slide past thick filaments, increasing overlap and shortening sarcomere without changing filament length.
  • Four steps of the cross bridge cycle?
    Cross bridge formation, power stroke, cross bridge detachment, and cocking of myosin head.
  • What triggers muscle fiber excitation at the neuromuscular junction?
    Release of acetylcholine (ACh) from motor neuron, binding to receptors on sarcolemma.
  • Describe the generation of an action potential in muscle fibers.
    End plate potential causes depolarization by opening voltage-gated Na+ channels, followed by repolarization via K+ channels.
  • What is excitation-contraction coupling?
    Process linking action potential propagation along sarcolemma to Ca2+ release from SR and muscle contraction.
  • How does Ca2+ regulate muscle contraction?
    Ca2+ binds to troponin, moving tropomyosin to expose myosin-binding sites on actin.
  • What is muscle twitch and its three phases?
    Single muscle fiber contraction with latent period, contraction phase, and relaxation phase.
  • Difference between isometric and isotonic contractions?
    Isometric: muscle tension increases without shortening; isotonic: muscle shortens and moves load.
  • Three pathways for ATP regeneration in muscle contraction?
    Direct phosphorylation by creatine phosphate, anaerobic glycolysis, and aerobic respiration.
  • What causes muscle fatigue?
    Ionic imbalances, increased inorganic phosphate, decreased glycogen, and interference with Ca2+ release.
  • What is excess postexercise oxygen consumption (EPOC)?
    Extra oxygen required to restore muscle to resting state after exercise.
  • Four factors affecting force of muscle contraction?
    Number of fibers stimulated, fiber size, frequency of stimulation, and degree of muscle stretch.
  • Three types of skeletal muscle fibers based on contraction speed and metabolism?
    Slow oxidative, fast oxidative, and fast glycolytic fibers.
  • Effects of aerobic vs resistance exercise on muscles?
    Aerobic increases capillaries, mitochondria, and endurance; resistance causes hypertrophy and strength.