Muscle Physiology Quiz
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Questions and Answers

Smooth muscle can be stimulated to contract by which of the following?

  • Nervous signals
  • Stretch of the muscle
  • Hormonal stimulation
  • All of the above (correct)

    • Where is smooth muscle found?

  • In the walls of hollow organs (correct)
  • In the heart muscles
  • In the tendons
  • In the skeletal muscles

    • Which type of smooth muscle contracts coordinately because the cells are linked by gap junctions?

  • Unitary smooth muscle (correct)
  • Multiunit smooth muscle
  • Visceral smooth muscle
  • Single unit smooth muscle

    • Which protein controls the interaction of actin and myosin in smooth muscle?

    <p>Calmodulin</p> Signup and view all the answers

    What regulates myosin-light-chain kinase in smooth muscle?

    <p>Ca2+</p> Signup and view all the answers

    Which type of smooth muscle has little or no coupling between cells?

    <p>Multiunit smooth muscle</p> Signup and view all the answers

    What is required to cause smooth muscle relaxation?

    <p>Calcium pump</p> Signup and view all the answers

    Which type of muscle fiber is densely innervated by postganglionic fibers of the parasympathetic and sympathetic nervous systems?

    <p>Smooth muscle fiber</p> Signup and view all the answers

    Smooth muscle contraction depends on the concentration of which ion in the extracellular fluid?

    <p>Calcium ion</p> Signup and view all the answers

    How long does a single smooth muscle contraction typically last?

    <p>Seconds</p> Signup and view all the answers

    Which type of muscle is made up of cells called muscle fiber or myocyte?

    <p>Skeletal muscle</p> Signup and view all the answers

    What percentage of the body is composed of skeletal muscle?

    <p>40%</p> Signup and view all the answers

    What is the diameter range of muscle fibers in skeletal muscles?

    <p>10-100 micrometers</p> Signup and view all the answers

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

    <p>To store calcium ions</p> Signup and view all the answers

    What is the role of titin in skeletal muscle?

    <p>To provide structural support</p> Signup and view all the answers

    What is the thinnest filament in a sarcomere?

    <p>Actin filament</p> Signup and view all the answers

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

    <p>To store and release calcium ions</p> Signup and view all the answers

    What is the role of myofibrils in skeletal muscle fibers?

    <p>To contract and produce force</p> Signup and view all the answers

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

    <p>To transmit electrical impulses</p> Signup and view all the answers

    What is the smallest unit of a myofibril that has the ability to contract?

    <p>Sarcomere</p> Signup and view all the answers

    Which proteins make up the thin filaments in skeletal muscle?

    <p>Actin, Tropomyosin, and Troponin</p> Signup and view all the answers

    What protein anchors the entire myofibrillar array to the cell membrane?

    <p>Dystrophin</p> Signup and view all the answers

    What is the term for all the muscle fibers innervated by a single nerve fiber?

    <p>Motor unit</p> Signup and view all the answers

    What triggers the release of calcium ions from the sarcoplasmic reticulum in skeletal muscle?

    <p>Activation of the ryanodine receptors</p> Signup and view all the answers

    What is the main source of energy for muscle contraction in the first few seconds?

    <p>ATP</p> Signup and view all the answers

    What happens to the tension in a contracting muscle as the actin and myosin filaments overlap?

    <p>The tension increases progressively</p> Signup and view all the answers

    In smooth muscle, what serves the same role as the Z disks in skeletal muscle?

    <p>Dense bodies</p> Signup and view all the answers

    What allows smooth muscle cells to contract as much as 80% of their length?

    <p>Actin filaments</p> Signup and view all the answers

    What is the name of the protein that binds up to 40 calcium ions in the sarcoplasmic reticulum?

    <p>Calsequestrin</p> Signup and view all the answers

    What happens to the tension in a contracting muscle as the sarcomere shortens?

    <p>The tension increases progressively</p> Signup and view all the answers

    Which type of muscle makes up about 40% of the body?

    <p>Skeletal muscle</p> Signup and view all the answers

    What is the diameter range of muscle fibers in skeletal muscles?

    <p>10-80 micrometers</p> Signup and view all the answers

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

    <p>To enclose the muscle fiber</p> Signup and view all the answers

    What is the name of the thin membrane enclosing a skeletal muscle fiber?

    <p>Sarcolemma</p> Signup and view all the answers

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

    <p>To transmit action potentials deep into the muscle fiber</p> Signup and view all the answers

    What surrounds the myofibrils in skeletal muscle fibers?

    <p>Sarcoplasmic reticulum</p> Signup and view all the answers

    What is the most small unit of the myofibril that has the ability to contract?

    <p>Sarcomere</p> Signup and view all the answers

    What protein keeps the myosin and actin filaments in place in skeletal muscle?

    <p>Titin</p> Signup and view all the answers

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

    <p>To store calcium ions</p> Signup and view all the answers

    What are skeletal muscles composed of?

    <p>Muscle fibers</p> Signup and view all the answers

    Which type of muscle contracts coordinately because the cells are linked by gap junctions?

    <p>Unitary smooth muscle</p> Signup and view all the answers

    What is the main source of energy for muscle contraction in smooth muscle?

    <p>ATP</p> Signup and view all the answers

    Where is smooth muscle found?

    <p>Digestive system</p> Signup and view all the answers

    What regulates myosin-light-chain kinase in smooth muscle?

    <p>Calmodulin</p> Signup and view all the answers

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

    <p>To store and release calcium ions</p> Signup and view all the answers

    What is the diameter range of muscle fibers in skeletal muscles?

    <p>1-10 micrometers</p> Signup and view all the answers

    What happens to the tension in a contracting muscle as the actin and myosin filaments overlap?

    <p>Tension increases</p> Signup and view all the answers

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

    <p>To transmit action potentials</p> Signup and view all the answers

    What is the role of myofibrils in skeletal muscle fibers?

    <p>To contract muscle fibers</p> Signup and view all the answers

    What happens to the tension in a contracting muscle as the sarcomere shortens?

    <p>Tension increases</p> Signup and view all the answers

    What is the role of dystrophin in skeletal muscle?

    <p>Anchoring the myofibrillar array to the cell membrane</p> Signup and view all the answers

    What triggers the release of acetylcholine (ACh) at the neuromuscular junction?

    <p>Nerve impulse reaching the neuromuscular junction</p> Signup and view all the answers

    What protein is responsible for carrying depolarization from the muscle cell surface to the interior of the fiber?

    <p>Dihydropyridine receptor (DHPR)</p> Signup and view all the answers

    What triggers the release of calcium ions from the sarcoplasmic reticulum in skeletal muscle?

    <p>Activation of the dihydropyridine receptor (DHPR)</p> Signup and view all the answers

    What is the main source of energy for muscle contraction in the first few seconds?

    <p>ATP</p> Signup and view all the answers

    What is the function of calsequestrin in the sarcoplasmic reticulum?

    <p>Binding up to 40 calcium ions</p> Signup and view all the answers

    What allows smooth muscle cells to contract as much as 80% of their length?

    <p>Actin filaments attached to dense bodies</p> Signup and view all the answers

    What protein controls the interaction of actin and myosin in smooth muscle?

    <p>Myosin-light-chain kinase</p> Signup and view all the answers

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

    <p>Cell membrane of the muscle fiber</p> Signup and view all the answers

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

    <p>Regulating the release and reaccumulation of calcium ions</p> Signup and view all the answers

    Study Notes

    Smooth Muscle

    • Can be stimulated to contract by various factors
    • Found in walls of hollow organs and tubes, such as blood vessels, digestive tract, and airways
    • Unitary smooth muscle contracts coordinately due to gap junctions between cells
    • Calmodulin controls the interaction of actin and myosin
    • Myosin-light-chain kinase is regulated by calcium and calmodulin
    • Multiunit smooth muscle has little or no coupling between cells
    • Relaxation requires a decrease in calcium ion concentration
    • Dense innervation by postganglionic fibers of the parasympathetic and sympathetic nervous systems
    • Contraction depends on extracellular calcium ion concentration
    • A single contraction typically lasts around 1-5 seconds

    Skeletal Muscle

    • Composed of cells called muscle fibers or myocytes
    • Makes up around 40% of the body
    • Muscle fibers have a diameter range of 10-100 μm
    • Transverse tubules (T-tubules) rapidly transmit the action potential to the interior of the fiber
    • Titin plays a role in muscle contraction and relaxation
    • The thinnest filament in a sarcomere is actin
    • Sarcoplasmic reticulum (SR) is the site of calcium ion storage and release
    • Myofibrils are the contractile units of skeletal muscle fibers
    • Sarcolemma is the plasma membrane of a muscle fiber
    • A sarcomere is the smallest unit of a myofibril that can contract
    • Thin filaments are composed of actin, tropomyosin, and troponin
    • Dystrophin anchors the entire myofibrillar array to the cell membrane
    • A motor unit is all the muscle fibers innervated by a single nerve fiber
    • Action potential triggers the release of calcium ions from the SR
    • Main source of energy for muscle contraction in the first few seconds is ATP and PCr
    • Tension decreases as the actin and myosin filaments overlap
    • Smooth muscle cells can contract up to 80% of their length due to the absence of Z-disks
    • Calsequestrin binds up to 40 calcium ions in the SR
    • Tension increases as the sarcomere shortens

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    Test your knowledge of the physiology of skeletal muscle and smooth muscle with this quiz by Prof. Dr. Dilek Özbeyli. Learn about muscle fibers, sarcolemma, and the somatic motor system. Discover fascinating facts about the composition of skeletal muscles and their relationship to smooth and cardiac muscle.

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