Excitation-Contraction Coupling and Cross-Bridge Cycle in Muscle Contraction
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Questions and Answers

What is the role of calcium in the Excitation-Contraction Coupling process?

  • Triggers the release of calcium from the T-tubules
  • Stimulates myosin to bind ATP
  • Inhibits the action potential propagation
  • Activates the ryanodine receptor to release stored calcium (correct)

What happens when myosin binds another ATP molecule?

  • It enters a state of rigor mortis
  • It detaches from actin (correct)
  • It activates the T-tubules
  • It binds stronger to actin

What occurs during the latent period of a twitch contraction?

  • Tension increases but not visibly
  • Peak tension is reached
  • Myosin binds to actin
  • AP propagation along T-tubules (correct)

How does an action potential contribute to muscle contraction?

<p>Increases cytosolic calcium levels (C)</p> Signup and view all the answers

What is the significance of the Cross-Bridge Cycle in muscle contraction?

<p>Facilitates the sliding of actin and myosin filaments (B)</p> Signup and view all the answers

When does muscle relaxation occur?

<p>When cytosolic calcium levels decrease (C)</p> Signup and view all the answers

What is the main reason for using acetylcholinesterase inhibitors in treating certain conditions?

<p>To inhibit the breakdown of acetylcholine, prolonging its action (C)</p> Signup and view all the answers

Why are glucocorticoids sometimes used in treatments related to neural causes?

<p>To decrease inflammation in neural tissues (C)</p> Signup and view all the answers

In smooth muscle cells, what is responsible for anchoring thin filaments in place during contraction?

<p>Dense bodies or dense plaques (D)</p> Signup and view all the answers

What is the characteristic feature of smooth muscles that distinguishes them from skeletal muscles regarding their striped appearance?

<p>Presence of sarcomeres (A)</p> Signup and view all the answers

In smooth muscle contraction, which protein directly binds with calcium ions to initiate the process?

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

What type of electrical activity allows some smooth muscle cells to generate action potentials without external signals?

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

What is the term for muscle contraction that produces tension and causes the muscle to change length?

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

What happens to the muscle length in eccentric contraction?

<p>The muscle lengthens (A)</p> Signup and view all the answers

What type of contraction occurs when the muscle changes tension but the length of the muscle stays the same?

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

What is the effect of increasing load on shortening velocity of a muscle?

<p>Shortening velocity decreases (B)</p> Signup and view all the answers

What does passive tension in a muscle refer to?

<p>Tension due to titin protein (B)</p> Signup and view all the answers

What happens to the tension in a muscle if a second action potential is produced before the muscle relaxes from the first?

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

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