Which of the following is a correct sequence of conduction systems of the human heart?

Appeared in: NIMHANS Nursing Officer - 2021

Explanation

The correct sequence of the heart's electrical conduction system begins with the sinoatrial (SA) node, the natural pacemaker.
The impulse then travels to the atrioventricular (AV) node, where it is momentarily delayed to allow for ventricular filling.
Following the AV node, the impulse is transmitted through the Bundle of His.
Finally, the impulse spreads via the Purkinje fibers, leading to the contraction of the ventricles.

Option A: This option incorrectly starts the sequence with the AV node. The SA node is the primary pacemaker and the starting point of the cardiac electrical impulse.
Option C: This option presents the conduction sequence in a completely reversed and incorrect order, starting from the ventricular components and moving backward.
Option D: This option incorrectly starts the sequence with the Purkinje fibers, which are the final part of the conduction pathway within the ventricles.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cardiac Conduction System as background academic context rather than a clinical decision trigger.
Understanding the normal conduction pathway is fundamental for interpreting electrocardiograms (ECGs) and identifying arrhythmias.
Disruptions in this pathway can lead to various heart blocks or tachycardias. For example, a block at the AV node can slow the heart rate (bradycardia) and may require a pacemaker.
The intrinsic rates of each component are a key safety mechanism. If the SA node fails, the AV node can take over as the pacemaker, albeit at a slower rate (40-60 bpm), providing a crucial backup rhythm.

How to Approach the Question

First, identify the core concept of the question, which is the sequence of the heart's electrical conduction.
Recall the starting point of the cardiac impulse. The heart's natural pacemaker is the Sinoatrial (SA) node.
Eliminate any options that do not begin with the SA node.
Trace the path of the impulse from the SA node: it goes to the atria and then converges at the Atrioventricular (AV) node.
From the AV node, recall that the impulse travels down the center of the heart through the Bundle of His.
Finally, remember that the impulse spreads throughout the ventricles via the Purkinje fibers to cause contraction. Select the option that follows this logical SA → AV → Bundle of His → Purkinje fibers sequence.

Concept Tested & Keywords

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E6 Pharmacology Nursing Lilley 11e Part 2 p. 84-86

E6 Physiology Essentials Sembulingam 10e Part 2 p. 170-172

E6 Medicine Harrison 22e Part 1 p. 1966-1968

Practise the full NIMHANS Nursing Officer - 2021

Attempt every question from this paper in a timed mock, then review the full solution for each one.