Transmission of Cardiac Impulse

Multiple Choice Questions (MCQs)

1. Where does the cardiac impulse originate?
   a) AV node
   b) Purkinje fibers
   c) SA node
   d) Bundle of His
   Answer: c) SA node
2. What is the total AV nodal delay?
   a) 0.03 seconds
   b) 0.09 seconds
   c) 0.13 seconds
   d) 0.22 seconds
   Answer: c) 0.13 seconds
3. What prevents backward transmission of impulses from the ventricles to the atria?
   a) AV node
   b) Purkinje fibers
   c) AV bundle
   d) Atrial musculature
   Answer: c) AV bundle
4. Which region has the slowest conduction velocity in the heart?
   a) SA node
   b) Atrial musculature
   c) AV node
   d) Purkinje fibers
   Answer: c) AV node
5. What is the conduction velocity of Purkinje fibers?
   a) 0.02 m/sec
   b) 0.05–0.1 m/sec
   c) 0.3–0.5 m/sec
   d) 1.5–4.0 m/sec
   Answer: d) 1.5–4.0 m/sec
6. What is the total time required for impulse conduction through the heart?
   a) 0.13 seconds
   b) 0.22 seconds
   c) 0.09 seconds
   d) 0.33 seconds
   Answer: b) 0.22 seconds
7. Which structure is the only pathway for conduction between the atria and ventricles?
   a) AV node
   b) AV bundle
   c) Internodal pathways
   d) Purkinje fibers
   Answer: b) AV bundle
8. Why is the AV nodal conduction slow?
   a) Plentiful gap junctions
   b) Small size and few gap junctions
   c) Rapid depolarization
   d) Long conduction fibers
   Answer: b) Small size and few gap junctions
9. How long does it take for the impulse to reach the AV node after originating from the SA node?
   a) 0.03 seconds
   b) 0.09 seconds
   c) 0.13 seconds
   d) 0.22 seconds
   Answer: a) 0.03 seconds
10. What is the conduction velocity in atrial muscles?
    a) 0.02 m/sec
    b) 0.05–0.1 m/sec
    c) 0.3–0.5 m/sec
    d) 1.5–4.0 m/sec
    Answer: b) 0.05–0.1 m/sec

Fill in the Blanks

1. The cardiac impulse reaches the AV node in ________ seconds after originating from the SA node.
   Answer: 0.03
2. The ________ fibers ensure rapid transmission of impulses to the ventricular musculature.
   Answer: Purkinje
3. The AV nodal delay allows the atria to discharge blood into the ________ before ventricular systole.
   Answer: ventricles
4. The ________ node has the slowest conduction velocity at 0.02 m/sec.
   Answer: AV
5. The total conduction time for the cardiac impulse is ________ seconds.
   Answer: 0.22

True or False

1. The Purkinje fibers have the fastest conduction velocity in the heart.
   Answer: True
2. The AV node directly connects to the ventricular musculature.
   Answer: False
3. Depolarization of the right atrium begins 0.01 seconds before the left atrium.
   Answer: True
4. The total nodal delay in the AV node and AV bundle is 0.09 seconds.
   Answer: False
5. The conduction velocity in cardiac muscle is slower than in Purkinje fibers.
   Answer: True

Subjective Questions

1. Describe the significance of the AV nodal delay in cardiac impulse transmission.
   Answer: The AV nodal delay, totaling 0.13 seconds, ensures that the atria have enough time to contract and discharge blood into the ventricles before the ventricles contract. This delay is crucial for efficient ventricular filling and optimal cardiac output.
2. Explain the role of Purkinje fibers in the transmission of the cardiac impulse.
   Answer: Purkinje fibers are specialized conductive fibers located at the ventricular apex. They ensure the rapid transmission of impulses to the ventricular musculature, enabling synchronized contraction of the ventricles. This rapid conduction helps maintain the efficiency of blood ejection from the ventricles into the systemic and pulmonary circulations.