Question
Right combination of velocity (m/s) and pacemaker conduction [beats/minute] for different parts of cardiac conduction system is/are?
A. SA node – 0.05 m/s & 60-100 b/m
B. AV node – 0.02-0.05 m/s & 40-55 b/m
C. Atrial myocardium – 1-1.2 m/s & 25-40 b/m
D. Bundle of His – 1.2-2 m/s & 25-40 b/m
E. Ventricular myocardium – 0.3-0.5 m/s & nil
Show Answer
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Correct Answer » A:B:D:E
Explanation
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Ans. A, B, D & E
The SA node discharges impulses at fastest rate, hence the rate at which SA node fires determines the heart rate, therefore, SA node is normal pacemaker of the heart,
The depolarization of the various parts of the heart proceeds in an orderly and timely way.
This is made possible by the presence of the conductive system of the heart which comprises the sinoatral node (SA node), internodal atrial pathways, atrioventricular node (AV node), bundle of his and its branches, and Purkinje system.
The conduction system is made up of modified cardiac muscles.
The fastest conduction is seen in Purkinje system and slowest in AV node and SA node.
