Cardiovascular physiology
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Questions and Answers

What is the main function of Purkinje fibers in the heart?

  • Control contraction of atria
  • Transmit electrical impulses from AV node to apex (correct)
  • Generate the lub-dub sound
  • Facilitate the closure of semilunar valves

    • Which phase in the cardiac contractile cells is characterized by a much larger release of Ca2+ known as Ca2+ sparks?

  • Repolarization phase
  • Plateau phase (correct)
  • Depolarization phase
  • Resting phase

    • What is the unique feature of the membrane potential in cardiac contractile cells during the plateau phase?

  • Drops to a negative level
  • Remains at resting membrane potential
  • Maintained close to the peak positive level (correct)
  • Fluctuates rapidly

    • Which component of an ECG represents the ventricular repolarization phase?

    <p>T wave</p> Signup and view all the answers

    What event in the heart causes the 'dub' sound in the cardiac cycle?

    <p>Closure of semilunar valves</p> Signup and view all the answers

    Which condition is characterized by disorganized and chaotic contraction of the ventricles?

    <p>Ventricular fibrillation</p> Signup and view all the answers

    What type of cells in the heart muscle are responsible for generating the pulse that causes contractions?

    <p>Autorhythmic cells</p> Signup and view all the answers

    Which type of nerve uses acetylcholine to bind to muscarinic receptors in the atria and slow the heart down?

    <p>Parasympathetic nerve</p> Signup and view all the answers

    What is the main ion movement responsible for giving rise to the pacemaker potential in autorhythmic cells?

    <p>Increased inward Na+ current</p> Signup and view all the answers

    What percentage of cardiac muscle cells do Contractile cells make up?

    <p>99%</p> Signup and view all the answers

    Which type of nerve uses noradrenaline and adrenaline to increase heart rate by binding to beta receptors of atria and ventricles?

    <p>Sympathetic nerve</p> Signup and view all the answers

    Where are most of the long-lasting Ca2+ channels located in contractile cells?

    <p>Transverse tubules</p> Signup and view all the answers

    What stimulates the opening of ryanodine receptor Ca2+ channels located on the sarcoplasmic reticulum?

    <p>Ca2+ influx from T tubules</p> Signup and view all the answers

    What distinguishes Autorhythmic cells from Contractile cells?

    <p>Autorhythmic cells don't contract</p> Signup and view all the answers

    Which of the following is not part of the normal electrical conduction pathway in the heart?

    <p>Internodal pathway</p> Signup and view all the answers

    What is the function of the AV node in the heart's electrical conduction system?

    <p>Delays the AP to allow atrial contraction to complete</p> Signup and view all the answers

    Which structure in the heart is known as the normal pacemaker?

    <p>SA node</p> Signup and view all the answers

    What is the primary role of Purkinje fibers in the heart?

    <p>Conduct electrical signals to the ventricles</p> Signup and view all the answers

    What is the role of autorhythmic cells in the heart?

    <p>Generating action potentials responsible for contraction</p> Signup and view all the answers

    Which ion movement is essential for the pacemaker potential in autorhythmic cells?

    <p>Increased inward Ca2+ current</p> Signup and view all the answers

    During which phase do contractile cells of the heart display pacemaker activity?

    <p>Resting phase</p> Signup and view all the answers

    What is the primary function of the autonomic nervous system in cardiac muscle excitation?

    <p>Controlling heart rate through neurotransmitter release</p> Signup and view all the answers

    Which type of nerve is responsible for slowing down the heart rate by binding to muscarinic receptors?

    <p>Vagus nerve</p> Signup and view all the answers

    During which phase in the cardiac contractile cells is the membrane potential maintained close to the peak positive level, leading to a much larger release of Ca2+ known as Ca2+ sparks?

    <p>Plateau phase</p> Signup and view all the answers

    Which specialized conducting fibers in the heart are larger than cardiomyocytes, have fewer myofibrils, and a large number of mitochondria, allowing for synchronized contractions of the ventricles?

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

    Which electrical structure in the heart transmits electrical impulses from the AV node to the apex of the heart?

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

    In cardiac excitation-contraction coupling, which ion's release from the sarcoplasmic reticulum induces muscle contraction in cardiac cells?

    <p>Calcium (Ca2+)</p> Signup and view all the answers

    Which phase in cardiac contractile cells is characterized by the maintenance of a membrane potential close to peak positivity due to a higher release of Ca2+ and is unique to these cells?

    <p>Plateau phase</p> Signup and view all the answers

    What is the primary function of the AV node in the heart's electrical conduction system?

    <p>Synchronization of atrial and ventricular contractions</p> Signup and view all the answers

    During which phase of the cardiac cycle does Ca2+ enter the cytosol from the T tubules stimulating the opening of Ca2+ channels on the sarcoplasmic reticulum?

    <p>Plateau phase</p> Signup and view all the answers

    Which component of the heart's electrical conduction system serves as the normal pacemaker and is responsible for generating the heart's electrical impulses?

    <p>SA node</p> Signup and view all the answers

    What is the purpose of the delay that occurs at the AV node in the heart's electrical conduction system?

    <p>To ensure complete atrial contraction before ventricular excitation begins</p> Signup and view all the answers

    Which part of the heart's electrical conduction system extends from the SA node to the AV node, ensuring coordination between the atria and ventricles?

    <p>Internodal pathway</p> Signup and view all the answers

    What is the role of the SA node in the heart's electrical conduction system?

    <p>SA node is the normal pacemaker of the heart.</p> Signup and view all the answers

    Describe the pathway of the interatrial pathway in the heart's electrical conduction system.

    <p>The interatrial pathway extends from the SA node within the right to the left atrium.</p> Signup and view all the answers

    What is the function of the AV node in cardiac excitation?

    <p>AV node serves as the only point of electrical contact between the atria and ventricles.</p> Signup and view all the answers

    How does the delay at the AV node impact the heart's electrical conduction system?

    <p>The delay at the AV node allows atrial contraction to be completed before ventricular excitation begins.</p> Signup and view all the answers

    Explain the significance of the Bundle of His in the heart's electrical conduction system.

    <p>The Bundle of His is responsible for relaying signals from the AV node to the Purkinje fibers.</p> Signup and view all the answers

    What is the primary function of Purkinje fibers in the heart?

    <p>Purkinje fibers are specialized for electrical conduction in the heart.</p> Signup and view all the answers

    How do Ca2+ sparks contribute to excitation-contraction coupling in cardiac muscle cells?

    <p>Ca2+ sparks lead to a much larger release of Ca2+ from the sarcoplasmic reticulum, inducing muscle contraction.</p> Signup and view all the answers

    What is the primary function of long-lasting Ca2+ channels in contractile cells?

    <p>Long-lasting Ca2+ channels in T tubules allow Ca2+ to enter the cytosol, leading to a larger Ca2+ release.</p> Signup and view all the answers

    Explain the concept of electrical excitation-contraction coupling between cardiac and skeletal muscle.

    <p>Electrical excitation in cardiac muscle must be complete before contraction begins to ensure coordinated function.</p> Signup and view all the answers

    What is the significance of the coordinated excitation between the atria and ventricles in the heart?

    <p>Coordinated excitation ensures that atrial contraction is complete before ventricular contraction begins.</p> Signup and view all the answers

    The SA node is responsible for delaying the signals to move to the Bundle of His.

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

    The interatrial pathway extends from the SA node within the right atrium to the left atrium.

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

    Excitation of the ventricles should be complete before atrial excitation occurs for proper cardiac function.

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

    The primary function of Purkinje fibers is to act as the normal pacemaker of the heart.

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

    During the refractory period, cardiac cells experience a period of increased excitability.

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

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