Block 2 Pace Quiz Skeletal Muscle: Micro Anatomy

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  • 1/21 Questions

    When the neurotransmitter is released and attached to the receptors on the sarcolemma. ____ rushes into the cell causing______ . which subsequently leads to the contraction process. Choose the correct pair of terms .

    • Na+, depotarization
    • Na+, repolarization
    • K+, depolarization
    • K+, repoanzation
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About This Quiz

This quiz titled 'Skeletal Muscle: Micro Anatomy' explores the intricate details of muscle fiber structure and function, focusing on neuromuscular junctions, nuclei placement, Z-lines, transverse tubules, and genetic factors affecting muscle performance. It assesses understanding vital for students of biology and medical sciences.

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  • 2. 

    The electrical signal of an action potential is conveyed into the interior of each muscle fiber by:

    • Sarcomeres.

    • Transverse tubules.

    • Sarcoplasmic reticulum

    • Z-lines.

    • Thick filaments,

    Correct Answer
    A. Transverse tubules.
    Explanation
    The electrical signal of an action potential is conveyed into the interior of each muscle fiber by transverse tubules. Transverse tubules, also known as T-tubules, are invaginations of the muscle cell membrane that extend deep into the muscle fiber. They allow the action potential to quickly spread throughout the entire muscle fiber, ensuring synchronous muscle contraction. The T-tubules are in close proximity to the sarcoplasmic reticulum, which stores and releases calcium ions necessary for muscle contraction. Together, the T-tubules and sarcoplasmic reticulum play a crucial role in the excitation-contraction coupling process in muscle cells.

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  • 3. 

    Which of the following is true for mammalian skeletal muscle?

    • T tubules are located at the Z disk

    • T tubules are absent

    • Troponin is absent

    • It possesses triads

    • It possesses caveolae

    Correct Answer
    A. It possesses triads
    Explanation
    Mammalian skeletal muscle possesses triads. Triads are structures formed by the close association of a T tubule and two terminal cisternae of the sarcoplasmic reticulum. This arrangement allows for the efficient release and uptake of calcium ions during muscle contraction and relaxation.

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  • 4. 

    Which of the following statements concerning triads in mammalian skeletal muscle is true?

    • They are located in the Z disk

    • They consist of two terminal cisternae of the sarcoplasmic reticulum separated by a T tubule

    • They can be observed with the light microscope

    • They are characterized by a T tubule that sequesters calcium ions

    • They consist of two T tubules separated by a central terminal cisterna

    Correct Answer
    A. They consist of two terminal cisternae of the sarcoplasmic reticulum separated by a T tubule
  • 5. 

    While you are holding a tray piled with dishes, an additional 5-pounds of dishes is placed on it. Your muscles that are holding the tray increase therr force of contraction through an increase

    • Length of the muscle

    • Number of motor units activated

    • Peak intracellular calcium concentration in the muscle

    • Strength of each cross-bridge interaction with actin

    • Maximum shortening velocity of the muscle

    Correct Answer
    A. Number of motor units activated
    Explanation
    When an additional 5-pounds of dishes is placed on the tray, the muscles holding the tray need to generate more force to counteract the increased weight. This increase in force is achieved by activating more motor units in the muscles. Motor units consist of a motor neuron and the muscle fibers it innervates. By activating more motor units, more muscle fibers are recruited, resulting in a greater force of contraction. Therefore, the number of motor units activated is the correct answer in this scenario.

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  • 6. 

    A 5-year-old boy sustains a tear in his gastrocnemius muscle when he is involved in a bicycle accident, Regeneration of the muscle will occur through which of the following?

    • Differentiation of satellite cells

    • Dedifferentiation of myocytes into myoblasts

    • Fusion of damaged myofibers to form new myotubes

    • Hyperplas ia of existing myofibers

    • Differentiation of fibroblasts to form myocytes

    Correct Answer
    A. Differentiation of satellite cells
    Explanation
    When a muscle is injured, satellite cells, which are a type of stem cell located on the surface of muscle fibers, are activated. These satellite cells have the ability to differentiate and fuse with existing muscle fibers to repair and regenerate the damaged muscle tissue. Therefore, the correct answer is differentiation of satellite cells.

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  • 7. 

    The sarcoplasmic reticulum of skeletal muscle functions in which of the following?

    • Cellular Ca++ storage

    • Cellular glycogen storage

    • Glycogen degradation

    • Transport of Ca++ into the terminal cisternae during muscle contraction

    • Ca++ release from the transverse tubules during muscle relaxation

    Correct Answer
    A. Cellular Ca++ storage
    Explanation
    The sarcoplasmic reticulum of skeletal muscle functions in cellular Ca++ storage. The sarcoplasmic reticulum is a specialized type of endoplasmic reticulum found in muscle cells. It plays a crucial role in regulating calcium ions within the muscle cell. During muscle contraction, calcium ions are released from the sarcoplasmic reticulum into the cytoplasm, which triggers the contraction. When the muscle relaxes, the sarcoplasmic reticulum actively pumps calcium ions back into its storage compartments, allowing the muscle to relax. Therefore, the sarcoplasmic reticulum functions as a storage site for calcium ions in the muscle cell.

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  • 8. 

    Which of the following is true of skeletal muscle myosin molecules?

    • Can be cleaved into light and heavy myoglobin by the proteolytic enzyme papain

    • Are attached to the Z line by a-actinin

    • Each has a head component that includes an actin-binding site

    • Can shorten to half their resting length during contraction

    • Have tail components that overlap In the I band

    Correct Answer
    A. Each has a head component that includes an actin-binding site
    Explanation
    Skeletal muscle myosin molecules have a head component that includes an actin-binding site. This means that the head of the myosin molecule can bind to actin filaments in the muscle fiber, forming cross-bridges. These cross-bridges are responsible for the sliding of actin filaments past myosin filaments, leading to muscle contraction.

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  • 9. 

    Which of the following chemicals would reduce neurotransmitter release at the neuromuscular junction synapse?

    • Botulinum toxin

    • Muscanne

    • Atropine

    • Curare

    • Pyridostiqmine

    Correct Answer
    A. Botulinum toxin
    Explanation
    Botulinum toxin is a neurotoxic protein produced by the bacterium Clostridium botulinum. It acts by blocking the release of acetylcholine, a neurotransmitter, at the neuromuscular junction synapse. By inhibiting the release of acetylcholine, botulinum toxin prevents the transmission of signals from nerve cells to muscle cells, leading to muscle paralysis. Therefore, it reduces neurotransmitter release at the neuromuscular junction synapse.

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  • 10. 

    Which of the following groups of terms is placed in order from smallest to largest?

    • Myofilament, myofibril, fiber, fascicle

    • Fiber, myofibril, myofilament, fascicle

    • Fascicle, fiber, myofilament, myofibril

    • Fascicle, fiber. myofibril, myofilament

    • Fiber. myofibril. fascicle, myofilament

    Correct Answer
    A. Myofilament, myofibril, fiber, fascicle
    Explanation
    The correct order from smallest to largest is myofilament, myofibril, fiber, fascicle. Myofilaments are the smallest components of muscle fibers, followed by myofibrils, which are bundles of myofilaments. Fibers are groups of myofibrils, and fascicles are bundles of fibers.

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  • 11. 

    Z-lines represent attachment sites for:

    • Thick filaments (myosin)

    • Thin filaments (actin)

    • T-tubules

    • Sarcoplasmic reticulum

    • Neuromuscular junctions

    Correct Answer
    A. Thin filaments (actin)
    Explanation
    Z-lines are structures found in skeletal muscle fibers that serve as attachment sites for thin filaments (actin). Thin filaments are composed of actin and other regulatory proteins and are responsible for muscle contraction. The Z-lines anchor the thin filaments and provide structural stability to the sarcomere, the basic unit of muscle contraction. Therefore, the correct answer is thin filaments (actin).

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  • 12. 

    Which of the following structures surrounds a muscle fascicle?

    • Endomysium

    • Epimysium

    • Fascia

    • Perimysium

    • Sarcoplasmic retinaculum

    Correct Answer
    A. Perimysium
    Explanation
    The perimysium is the correct answer because it is the connective tissue layer that surrounds a muscle fascicle. It is responsible for providing support and protection to the fascicle, as well as allowing for the transmission of blood vessels and nerves to the muscle fibers within the fascicle.

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  • 13. 

    Assuming two skeletal muscle fibers have the same myosin ATPase activity, and both are producing an equal force, but one fiber is longer than the other one, Which of the following best describes their shortening velocities?

    • Long fiber has a higher velocity during isotonic contraction than the short one

    • Long fiber has a higher velocity during isometric contraction than the short one

    • Long fiber has a lower velocity during isotonic contraction than the short one

    • Long fiber has a lower velocity during isometric contraction than the short one

    • Both fibers have the same velocity during isotonic contraction

    Correct Answer
    A. Long fiber has a higher velocity during isotonic contraction than the short one
    Explanation
    In skeletal muscle, the length of the fiber affects the shortening velocity during isotonic contraction. The longer fiber has a higher velocity because it has a greater distance to cover in the same amount of time. Isometric contraction, on the other hand, does not involve any change in length, so the length of the fiber does not affect the velocity. Therefore, the long fiber has a higher velocity during isotonic contraction than the short one.

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  • 14. 

    Which of the following is true of motor units?

    • Are found only in cardiac muscle

    • Are largest in muscles responsible for delicate movements

    • Consist of a muscle fiber and all the nerves that supply it

    • Consist of a motor neuron and all the muscles it supplies

    • Are the same as myoneural junctions

    Correct Answer
    A. Consist of a motor neuron and all the muscles it supplies
    Explanation
    Motor units consist of a motor neuron and all the muscles it supplies. This means that a single motor neuron can control multiple muscle fibers. When the motor neuron is activated, all the muscle fibers it innervates will contract simultaneously. This allows for coordinated and synchronized muscle movements.

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  • 15. 

    The many nuclei of a skeletal muscle fiber are located:

    • Midway along the length of the muscle fiber,

    • Spaced at regular intervals along each muscle fiber

    • Spaced at irregular intervals along each muscle fiber.

    • Near the proximal end of a muscle fiber.

    • Near the distal end of a muscle fiber.

    Correct Answer
    A. Spaced at irregular intervals along each muscle fiber.
    Explanation
    The correct answer is spaced at irregular intervals along each muscle fiber. Skeletal muscle fibers are multinucleated, meaning they contain multiple nuclei. These nuclei are not evenly spaced along the length of the muscle fiber, but rather are located at irregular intervals. This arrangement allows for efficient control and coordination of muscle contraction, as different regions of the muscle fiber can be activated independently.

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  • 16. 

    The endomysium is a connective tissue investment that surrounds

    • Individual muscle fibers

    • Muscle fascicles

    • Individual myofibrils

    • An entire muscle

    • Small bundles of muscle cells

    Correct Answer
    A. Individual muscle fibers
    Explanation
    The endomysium is a connective tissue investment that surrounds individual muscle fibers. This connective tissue layer provides support and protection to the muscle fibers, allowing them to function properly. It also helps to maintain the structural integrity of the muscle and allows for efficient transmission of force during muscle contraction.

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  • 17. 

    Membrane depolarization occurs in skeletal muscle fibers in which order after acetylcholine crosses the synaptic cleft?

    • T tubule, terminal cisternae, sarcoplasmic retinaculum, sarcolemma

    • Sarcoplasmic retinaculum, T tubule, presynaptic membrane, sarcolemma

    • Terminal cisternae, sarcolemma, sarcoplasmic retinaculum, caveolae

    • Sarcolemma, T tubule, terminal cisternae, sarcoplasmic retinaculum

    • Sarcolemma, sarcoplasmic retinaculum, T tubule, terminal cisternae

    Correct Answer
    A. Sarcolemma, T tubule, terminal cisternae, sarcoplasmic retinaculum
    Explanation
    After acetylcholine crosses the synaptic cleft, it binds to receptors on the sarcolemma, which triggers the opening of sodium channels. This leads to the depolarization of the sarcolemma. The depolarization then spreads down the T tubules, which are invaginations of the sarcolemma. The T tubules are in close proximity to the terminal cisternae of the sarcoplasmic reticulum, which releases calcium ions in response to the depolarization. The calcium ions then bind to troponin, initiating muscle contraction. Therefore, the correct order of membrane depolarization in skeletal muscle fibers is sarcolemma, T tubule, terminal cisternae, sarcoplasmic reticulum.

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  • 18. 

    Neuromuscular Junctions are located

    • Midway along the length of the muscle fiber

    • Spaced at regular intervals along each muscle fiber.

    • Spaced at irregular intervals along each muscle fiber

    • Near the proximal end of a muscle fiber,

    • Near the distal end of a muscle fiber.

    Correct Answer
    A. Midway along the length of the muscle fiber
    Explanation
    Neuromuscular junctions are located midway along the length of the muscle fiber. This is because the neuromuscular junction is the point where the motor neuron meets the muscle fiber, and it is responsible for transmitting the nerve impulse from the neuron to the muscle fiber, causing muscle contraction. Placing the neuromuscular junction midway along the length of the muscle fiber allows for efficient transmission of the nerve impulse to all parts of the muscle, ensuring coordinated and synchronized muscle contractions.

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  • 19. 

    In an experiment. you want to shorten the duration of a skeletal muscle contraction There are different poss ibilities to achieve this goal. One is:

    • To block the Ca++ ATPase activity of cell membrane

    • To block the Ca++ ATPase activity of scarcoplasmic membrane

    • To increase the Ca++ entry through DHP receptors

    • To increase Ca++ release through ryanodin receptors

    • To increase the activity of Ca++/3Na+ exchanger

    Correct Answer
    A. To increase the activity of Ca++/3Na+ exchanger
    Explanation
    To increase the activity of the Ca++/3Na+ exchanger would result in an increase in the exchange of calcium ions (Ca++) with sodium ions (Na+) across the cell membrane. This would lead to a decrease in the concentration of calcium ions within the cell, which would ultimately shorten the duration of a skeletal muscle contraction.

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  • 20. 

    A 13-year-old boy presents with episodes of extreme proximal muscle weakness lasting an hour or more The episodes are precipitated by rest following strenuous exercise His father and paternal grandmother have suffered similar symptoms with onset at adolescence. An electromyogram, periormed during an attack, reveals normal skeletal muscle action potentials in response to effort. It is not surprising that the disease is associated with:

    • A mutation in the voltage sensuive K+ channel of skeletal muscle

    • Elevated PIP2 in skeletal muscle

    • Depressed PIP2 and elevated IP3 in gamma-motoneurons of the penpheral nerves

    • A mutation in acetylcholine esterase

    • A mutation in the voltage sensitive Ca2+ channel of skeletal muscle

    Correct Answer
    A. A mutation in the voltage sensitive Ca2+ channel of skeletal muscle
    Explanation
    The correct answer is a mutation in the voltage-sensitive Ca2+ channel of skeletal muscle. This is because the patient's symptoms of extreme proximal muscle weakness, which are precipitated by rest following strenuous exercise, are consistent with a condition known as hypokalemic periodic paralysis. This condition is caused by mutations in the voltage-sensitive Ca2+ channel, which leads to abnormal muscle excitability and periodic episodes of muscle weakness.

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  • 21. 

    Which of the following is true of T tubules?

    • Are evaginations of the sarcoplasmic retinaculum

    • Sequester calcium ions during muscle relaxation

    • Carry repolarization to the muscle fiber interior

    • Are found overlying the A-I band junction in cardiac muscle cells

    • Contain a rich supply of acetylcholine receptors

    Correct Answer
    A. Carry repolarization to the muscle fiber interior
    Explanation
    T tubules are invaginations of the sarcolemma that extend deep into the muscle fiber. They play a crucial role in carrying the action potential from the sarcolemma to the interior of the muscle fiber, allowing for the depolarization and repolarization of the muscle cell during muscle contraction and relaxation. This helps to ensure synchronized and efficient muscle contraction. Therefore, the statement "Carry repolarization to the muscle fiber interior" is true of T tubules.

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  • Current Version
  • Mar 20, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Oct 26, 2011
    Quiz Created by
    Chachelly
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