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Muscular System - Anatomy & Physiology

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  • What are the three basic muscle types found in the body?

    Skeletal muscle, cardiac muscle, and smooth muscle.

  • What prefixes refer to muscle and flesh in muscle terminology?

    myo- and mys- refer to muscle; sarco- refers to flesh.

  • Describe the characteristics of skeletal muscle cells.

    Large, cigar-shaped, multinucleate, striated, voluntary muscle fibers attached to bones by tendons.

  • What connective tissue layers surround skeletal muscle fibers?

    Endomysium encloses single fibers, perimysium wraps fascicles, epimysium covers entire muscle, and fascia lies outside epimysium.

  • What are tendons and aponeuroses?

    Tendons are cordlike collagen structures attaching muscle to bone; aponeuroses are sheetlike connective tissues attaching muscles indirectly.

  • What are the key features of smooth muscle?

    Spindle-shaped, uninucleate, no striations, involuntary, found in walls of hollow organs, slow and sustained contractions.

  • What distinguishes cardiac muscle cells?

    Striated, involuntary, uninucleate, branching cells connected by intercalated discs, contracts at pacemaker-set rate.

  • What are the three additional roles of skeletal muscle besides movement?

    Maintain posture, stabilize joints, and generate heat.

  • What is the sarcolemma?

    The specialized plasma membrane of a skeletal muscle fiber.

  • What causes the striated appearance of skeletal muscle?

    Alternating light (I) bands and dark (A) bands formed by arrangement of thin and thick myofilaments.

  • What is a sarcomere?

    The contractile unit of a muscle fiber, composed of organized thick (myosin) and thin (actin) filaments.

  • What is the role of myosin heads in muscle contraction?

    Myosin heads form cross bridges by attaching to actin filaments and pivot to slide filaments during contraction.

  • What is the function of the sarcoplasmic reticulum in muscle fibers?

    Stores and releases calcium ions, which trigger muscle contraction.

  • Define irritability and contractility in muscle tissue.

    Irritability is the ability to respond to stimuli; contractility is the ability to shorten forcibly.

  • What is a motor unit?

    One motor neuron and all the skeletal muscle fibers it stimulates.

  • What neurotransmitter stimulates skeletal muscle contraction?

    Acetylcholine (ACh) released at the neuromuscular junction.

  • What happens during depolarization of the muscle fiber membrane?

    Sodium ions enter the cell, making the interior more positive and generating an action potential.

  • What enzyme breaks down acetylcholine to end muscle contraction?

    Acetylcholinesterase (AChE) breaks down ACh into acetic acid and choline.

  • What is the sliding filament theory of muscle contraction?

    Calcium binds to thin filaments exposing myosin-binding sites; myosin heads attach and pivot, sliding thin filaments toward sarcomere center.

  • How is ATP regenerated during muscle contraction?

    By direct phosphorylation of ADP by creatine phosphate, aerobic respiration, and anaerobic glycolysis.

  • What causes muscle fatigue?

    Ion imbalances, oxygen deficit, lactic acid buildup, and decreased ATP supply during prolonged strenuous activity.

  • Differentiate isotonic and isometric muscle contractions.

    Isotonic: muscle shortens and movement occurs; Isometric: muscle tension increases but length stays the same.

  • What is muscle tone?

    Continuous partial contraction of muscles due to systematic stimulation of different motor units, keeping muscles firm and ready.

  • How does aerobic exercise affect muscles?

    Increases muscle strength, flexibility, endurance, metabolism efficiency, and resistance to fatigue.

  • How does resistance (strength) training affect muscles?

    Increases muscle size and strength by enlarging individual muscle fibers.