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Anatomy & Physiology: Muscle Tissue and Contraction

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  • What are the three types of muscle tissue?

    Skeletal, Cardiac, and Smooth muscle tissues.

  • Key characteristics of skeletal muscle tissue

    Long cylindrical fibers, striated, voluntary control, attached to bones and skin, contracts rapidly but tires easily.

  • Key characteristics of cardiac muscle tissue

    Found only in heart, striated, involuntary, contracts at steady rate due to pacemaker, branching chains of cells.

  • Key characteristics of smooth muscle tissue

    Found in walls of hollow organs, spindle-shaped cells, 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.

  • Connective tissue sheaths of 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 or less movable bone; insertion attaches to movable bone.

  • What is a sarcomere?

    The smallest contractile unit of a muscle fiber, extending from one Z disc to the next.

  • Composition of thick and thin filaments in muscle fibers

    Thick filaments are made of myosin; thin filaments are made of actin, tropomyosin, and troponin.

  • Role of sarcoplasmic reticulum in muscle contraction

    Stores and releases Ca2+ ions to trigger muscle contraction.

  • Function of T tubules in muscle fibers

    Transmit electrical impulses deep into muscle fiber to trigger Ca2+ release from SR.

  • Sliding filament model of muscle contraction

    Thin filaments slide past thick filaments, increasing overlap and shortening the sarcomere without changing filament length.

  • Four steps of the cross bridge cycle

    1. Cross bridge formation, 2. Power stroke, 3. Cross bridge detachment, 4. Cocking of myosin head.

  • Events at the neuromuscular junction during muscle contraction

    AP arrives, Ca2+ enters axon terminal, ACh released, binds to receptors, Na+ enters muscle fiber, end plate potential generated.

  • Three phases of action potential generation in muscle fiber

    End plate potential, depolarization, and repolarization.

  • What is excitation-contraction coupling?

    Process linking AP propagation along sarcolemma and T tubules to Ca2+ release and muscle contraction.

  • Difference between isotonic and isometric muscle contractions

    Isotonic: muscle changes length and moves load; Isometric: muscle tension increases but length stays the same.

  • Three mechanisms for ATP regeneration in muscle

    Direct phosphorylation by creatine phosphate, anaerobic glycolysis, and aerobic respiration.

  • Factors affecting force of muscle contraction

    Number of fibers stimulated, fiber size, frequency of stimulation, and degree of muscle stretch.

  • Types of skeletal muscle fibers based on contraction speed and metabolism

    Slow oxidative, fast oxidative, and fast glycolytic fibers.

  • What is muscle fatigue and its possible causes?

    Inability to contract despite stimulation; caused by ionic imbalances, increased Pi, decreased ATP, and glycogen depletion.

  • What is excess postexercise oxygen consumption (EPOC)?

    Extra oxygen required to restore muscle to resting state after exercise.

  • What is a motor unit?

    A motor neuron and all the muscle fibers it innervates.

  • What is muscle tone?

    Constant, slight contraction of muscles due to spinal reflexes, keeping muscles firm and ready.