Skeletal Muscle Basics
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Questions and Answers

What is the primary function of the sarcoplasm in skeletal muscle fibers?

  • Provision of ATP for muscle contraction (correct)
  • Conduction of action potentials
  • Storage of Ca2+ ions
  • Maintenance of the transmembrane potential

    • Which of the following is NOT a characteristic of skeletal muscle?

  • Ability to initiate their own contraction (correct)
  • Support of soft tissue
  • Controlled by the somatic nervous system
  • Voluntary contraction

    • What is the primary function of the transverse tubules (T-tubules) in skeletal muscle fibers?

  • Storage of Ca2+ ions
  • Regulation of muscle contraction
  • Passage of nerve messages directly to the sarcoplasmic reticulum (correct)
  • Conduction of action potentials

    • What is the purpose of the extensive vascular system in skeletal muscle?

    <p>To supply oxygen and nutrients, and to carry away wastes (C)</p> Signup and view all the answers

    What is the role of the sarcoplasmic reticulum (SR) in skeletal muscle fibers?

    <p>Storage of Ca2+ ions (D)</p> Signup and view all the answers

    Which of the following is a characteristic of skeletal muscle fibers?

    <p>Development from myoblasts (A)</p> Signup and view all the answers

    What is the purpose of the connective tissue (epimysium, perimysium, endomysium) in skeletal muscle?

    <p>To provide structural support to the muscle (C)</p> Signup and view all the answers

    What is the role of the sarcolemma in skeletal muscle fibers?

    <p>Maintenance of the transmembrane potential (C)</p> Signup and view all the answers

    In the T-tubule membrane, what is the function of DHPR?

    <p>Voltage-gated sensors (B)</p> Signup and view all the answers

    What is the primary function of Troponin-C?

    <p>Binding to Ca2+ ions (A)</p> Signup and view all the answers

    What is the main component of thick fibers in myofibrils?

    <p>Myosin (C)</p> Signup and view all the answers

    What is the function of Nebulin in myofibrils?

    <p>Non-elastic anchor (C)</p> Signup and view all the answers

    What is the structure formed by a transverse tubule flanked by two terminal cisternae?

    <p>Triad (D)</p> Signup and view all the answers

    What is the function of Tropomyosin in resting muscle cells?

    <p>Prevents muscle contraction (A)</p> Signup and view all the answers

    What is the binding site for actin in myofibrils?

    <p>Heavy chain of myosin (C)</p> Signup and view all the answers

    What is the function of Titin in myofibrils?

    <p>Keeps the myosin and actin in place (D)</p> Signup and view all the answers

    Study Notes

    Muscle Structure and Function

    • A/I bands and H zones are fused together in skeletal muscle.
    • DHPR (Dihydropyridine receptor) is a voltage-gated sensor in the T-tubule membrane.
    • RYR (Ryanodine Receptor) is a Ca2+ release channel in the SR membrane.

    Muscle Fiber Components

    • Myofibrils: site of contraction, consisting of thick and thin filaments.
    • Thick filaments: • Made up of myosin, composed of 2 heavy chains and 4 light chains. • Heavy chain is the motor domain for binding ATP and releasing to create movement.
    • Thin filaments: • Actin: a globular protein that polymerizes to form F-actin filaments. • Tropomyosin: a strand protein wrapped spirally around F-actin filaments. • Troponin: a complex of 3 subunits (T, I, and C) that regulate muscle contraction.

    Troponin and Muscle Contraction

    • Troponin-C binds to 4 Ca2+ ions, initiating muscle contraction.
    • In the absence of Ca2+, tropomyosin inhibits myosin head attachment to actin, preventing contraction.
    • When Ca2+ binds to troponin, the complex shifts, allowing myosin heads to bind to actin and initiate contraction.

    Skeletal Muscle Characteristics

    • Contract in response to signals from somatic motor neurons.
    • Cannot initiate their own contraction.
    • Functions: movement, maintaining posture, supporting soft tissue, and storing nutrient reserves.

    Skeletal Muscle Structure

    • Consists of muscle fibers developed from myoblasts.
    • Surrounded by connective tissue (epimysium, perimysium, and endomysium).
    • Nerves: controlled by somatic nervous system, with each fiber supplied with nerve endings that control contraction.
    • Blood vessels: extensive vascular system supplies oxygen and nutrients and removes waste.

    Muscle Fiber Components

    • Sarcolemma: maintains transmembrane potential.
    • Sarcoplasm: rich in glycogen and myoglobin, providing ATP for muscle contraction.
    • Myofibrils and sarcoplasmic reticulum (SR): site of muscle contraction and Ca2+ storage.

    Transverse Tubules (T-Tubules) and Sarcoplasmic Reticulum (SR)

    • T-tubules: passageways from extracellular space to terminal cisternae of SR, allowing nerve message and nutrient passage.
    • SR: stores Ca2+ at rest, releasing it upon stimulation, and pumping it back in the absence of stimulation.

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    Test your knowledge on the basics of skeletal muscles, including their characteristics, functions, and mechanisms of contraction.

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