T-Tubules and SR in Cardiac Cells
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Questions and Answers

Which part of the cardiac muscle is responsible for storing and releasing calcium ions (Ca2+) for excitation-contraction coupling?

  • Sarcoplasmic reticulum (SR) (correct)
  • Mitochondria
  • T-tubules
  • Thick filaments
  • Where are T-tubules located in the cardiac muscle?

  • In the ventricles
  • In the atria
  • Close to the contractile elements
  • At the Z lines (correct)
  • What is the main component of the thick filaments in cardiac muscle?

  • F-actin
  • Tropomyosin
  • Meromyosin/myosin (correct)
  • Troponin (C, I, T)
  • Which property of muscle cells allows them to respond to stimuli and initiate an action potential?

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

    What term refers to the ability of certain cells, like the sinoatrial node, to initiate their own electrical activity?

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

    Which property of muscle cells enables them to generate force and shorten?

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

    Which type of cardiac cells exhibit slow response action potentials?

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

    Which phase of the cardiac action potential is characterized by rapid upstroke?

    <p>Phase 0</p> Signup and view all the answers

    Where is the intrinsic pacemaker of the heart located?

    <p>Right atrium</p> Signup and view all the answers

    During which phase of the cardiac action potential does potassium ion (K+) efflux cause early repolarization?

    <p>Phase 1</p> Signup and view all the answers

    What is the primary ion responsible for the depolarization phase (phase 0) of the SA node action potential?

    <p>Sodium ions (Na+)</p> Signup and view all the answers

    What causes the repolarization in phase 3 of the cardiac action potential?

    <p>Outward potassium ion (K+) current</p> Signup and view all the answers

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