Excitation-Contraction Coupling in Smooth Muscle
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Excitation-Contraction Coupling in Smooth Muscle

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Questions and Answers

What is the role of mucopolysaccharides within the T tubules of cardiac muscle fibers?

  • Binding calcium ions (correct)
  • Regulating potassium ion concentration
  • Generating action potentials
  • Facilitating sodium ion diffusion

    • Why does a heart placed in a calcium-free solution stop beating?

  • The sodium-calcium exchanger malfunctions
  • T tubules allow percolation of extracellular fluid containing calcium ions (correct)
  • The sarcoplasmic reticulum is unable to release calcium ions
  • Cardiac muscle fiber contraction depends on calcium ion concentration

    • How does the strength of cardiac muscle contraction relate to extracellular fluid calcium concentration?

  • It remains unaffected by changes in calcium concentration
  • It is greatly influenced by extracellular fluid calcium concentration (correct)
  • It depends on the level of sodium-potassium ATPase pump activity
  • It is solely dependent on intracellular calcium levels

    • Why is skeletal muscle contraction less affected by changes in extracellular fluid calcium concentration compared to cardiac muscle contraction?

    <p>Skeletal muscle relies mainly on intracellular calcium ions for contraction</p> Signup and view all the answers

    How are calcium ions removed from cardiac muscle cells?

    <p>By a sodium-calcium exchanger</p> Signup and view all the answers

    What is the main difference in calcium ion release between skeletal muscle and cardiac muscle?

    <p>In cardiac muscle, calcium ions also diffuse from T tubules in addition to being released from the sarcoplasmic reticulum.</p> Signup and view all the answers

    What triggers the release of calcium into the sarcoplasm in cardiac muscle?

    <p>Activation of calcium release channels in the sarcoplasmic reticulum membrane by calcium entering the cell.</p> Signup and view all the answers

    Why would the strength of cardiac muscle contraction be reduced without calcium from the T tubules?

    <p>Sarcoplasmic reticulum of cardiac muscle does not store enough calcium for full contraction.</p> Signup and view all the answers

    What is the role of troponin in initiating contraction in both skeletal and cardiac muscles?

    <p>Interacting with calcium ions to initiate cross-bridge formation.</p> Signup and view all the answers

    What happens when voltage-dependent calcium channels in T tubules open during an action potential?

    <p>Calcium ions diffuse into the sarcoplasm from the T tubules.</p> Signup and view all the answers

    Why are the T tubules in cardiac muscle larger in diameter compared to those in skeletal muscle?

    <p>To allow for a greater volume of diffusion of calcium ions into the sarcoplasm.</p> Signup and view all the answers

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