Muscle physiology
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Questions and Answers

What happens during the relaxation phase of muscle fibre tension?

  • Cross-bridges form and sarcomeres shorten
  • No contraction occurs
  • Calcium ions are pumped back into the sarcoplasmic reticulum (correct)
  • Tension peaks

    • Which statement is true about tetanus in muscle contraction?

  • It occurs during the latent period
  • Muscle fibre is stimulated so rapidly that it cannot relax between stimuli (correct)
  • Twitches are added together to create sustained maximal contraction
  • Calcium ions are released from the sarcoplasmic reticulum

    • What causes rigor mortis to occur in muscles after death?

  • Overproduction of sarcomeres
  • No fresh ATP available to detach myosin and actin complexes (correct)
  • Excessive calcium ions in muscle cells
  • Intense physical activity before death

    • What is the primary function of the intercalated discs in cardiac muscle?

    <p>Facilitate communication between adjacent cardiac muscle cells</p> Signup and view all the answers

    During which phase of muscle fibre tension does no contraction occur?

    <p>Latent period</p> Signup and view all the answers

    What maintains muscle tone in skeletal muscles?

    <p>A small amount of contraction within the muscle fibre</p> Signup and view all the answers

    What characterizes smooth muscle cells?

    <p>Controlled by autonomic nervous system</p> Signup and view all the answers

    How does summation differ from twitch contraction?

    <p>Summation occurs when twitches are added together, while twitch contraction is a singular event</p> Signup and view all the answers

    What is the functional unit of skeletal muscle?

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

    Which protein allows the muscle to return to its initial length after being stretched?

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

    What is the primary function of troponin in muscle contraction?

    <p>Interacts with calcium</p> Signup and view all the answers

    What is the role of tropomyosin in muscle contraction?

    <p>Reacts with troponin</p> Signup and view all the answers

    What happens after the action potential travels to the skeletal muscle fibre?

    <p>Excitation-contraction coupling</p> Signup and view all the answers

    Which protein interacts with actin during muscle contraction?

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

    What specific receptors on the surface of transverse tubules are activated by voltage?

    <p>Dihydropyridine receptors</p> Signup and view all the answers

    Which protein contains a myosin binding site on actin?

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

    What is the role of Ca2+ released by the sarcoplasmic reticulum?

    <p>Binds to the Ca2+ binding site on troponin</p> Signup and view all the answers

    What happens when ATP is hydrolyzed during the cross bridge cycle?

    <p>Detaches myosin from actin</p> Signup and view all the answers

    Which molecule energizes the myosin by splitting ATP during muscle contraction?

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

    During muscle contraction, what role does tropomyosin play with respect to myosin heads binding to actin?

    <p>Prevents it by binding to myosin heads</p> Signup and view all the answers

    What is the main role of the dihydropyridine receptors on the transverse tubules?

    <p>Initiate a permeability change in the sarcoplasmic reticulum</p> Signup and view all the answers

    What initiates the power stroke during muscle contraction?

    <p>$\text{ADP and Pi}$ bound to myosin</p> Signup and view all the answers

    What is the role of troponin in muscle contraction?

    <p>Troponin binds to calcium ions and moves tropomyosin aside to expose the actin binding sites for myosin.</p> Signup and view all the answers

    How does titin protein contribute to muscle function?

    <p>Titin is a large protein that provides elasticity and stabilizes the position of the myosin filaments in the sarcomere.</p> Signup and view all the answers

    Explain the process of excitation-contraction coupling in muscle cells.

    <p>Excitation-contraction coupling is the process by which an action potential triggers calcium release from the sarcoplasmic reticulum, leading to the formation of cross-bridges between actin and myosin filaments.</p> Signup and view all the answers

    What is the function of tropomyosin in muscle contraction?

    <p>Tropomyosin regulates the interaction between actin and myosin by blocking the myosin binding sites on actin in the absence of calcium ions.</p> Signup and view all the answers

    How do actin filaments contribute to muscle contraction?

    <p>Actin filaments provide the binding sites for myosin heads, allowing the formation of cross-bridges and the sliding of filaments during muscle contraction.</p> Signup and view all the answers

    What is the primary function of the troponin complex in muscle cells?

    <p>The troponin complex regulates the interaction between actin and myosin by binding calcium ions and initiating muscle contraction.</p> Signup and view all the answers

    How does tropomyosin contribute to muscle relaxation?

    <p>Tropomyosin covers the myosin binding sites on actin in the absence of calcium ions, preventing cross-bridge formation and promoting muscle relaxation.</p> Signup and view all the answers

    What is the significance of actin-myosin cross-bridges in muscle contraction?

    <p>Actin-myosin cross-bridges generate force by sliding past each other, leading to the shortening of sarcomeres and muscle contraction.</p> Signup and view all the answers

    How does the sliding filament theory explain muscle contraction?

    <p>The sliding filament theory states that muscle contraction occurs when actin filaments slide past myosin filaments, causing the sarcomere to shorten.</p> Signup and view all the answers

    What role does the troponin-tropomyosin complex play in regulating muscle contraction?

    <p>The troponin-tropomyosin complex blocks myosin binding sites on actin in the absence of calcium ions, preventing muscle contraction.</p> Signup and view all the answers

    Troponin is a fibrous protein found in skeletal muscle cells.

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

    Titin is responsible for the power stroke during muscle contraction.

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

    Tropomyosin interacts with calcium ions during muscle contraction.

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

    Actin filaments are made up of myosin and actin proteins.

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

    Excitation-contraction coupling is the sequence of events that link the muscle contraction to the action potential at the neuromuscular junction.

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

    Group of muscle fibres is enveloped by which connective tissue.

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

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