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Following are the stages of pathway for conduction of an action potential through the heart: A. AV bundle B. Purkinje fibres C. AV node D. Bundle branches E. SA node Choose the correct sequence of pathway from the options given below:
SA node (Pacemaker E) -> AV node (C) -> AV bundle of His (A) -> Bundle branches (D) -> Purkinje fibres (B)! Sequence: E -> C -> A -> D -> B!
The sino-atrial node (SAN) can generate the maximum number of action potentials, i.e., 70-75 min⁻¹, and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called the pacemaker (Stage E).
The action potential spreads from the SAN to the atrio-ventricular node (AVN) situated in the lower left corner of the right atrium close to the atrio-ventricular septum (Stage C). From the AVN, an atrioventricular bundle (AV bundle / bundle of His) continues that divides into a right and left bundle (Stages A and D).
These branches give rise to minute fibres throughout the ventricular musculature of the respective sides called Purkinje fibres (Stage B), causing simultaneous ventricular contraction.
Diagnose every choice: Know exactly why the right option works and why distractors fail.
Starts at Purkinje fibres instead of the pacemaker.
Places AV node at the end instead of directly after SA node.
Accurately traces anatomical conduction: SA node -> AV node -> AV bundle -> Bundle branches -> Purkinje fibres.
Places AV bundle before SA node.
Swapping AV node and AV bundle in the sequence.
"The SAN can generate the maximum number of action potentials... An atrio-ventricular bundle continues from the AVN which passes through the atrio-ventricular septa to emerge on the top of the interventricular septum and immediately divides into a right and left bundle. These branches give rise to minute fibres called Purkinje fibres."
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