Regarding the conducting system of the heart, identify the wrong statement?

Appeared in: AIIMS Raipur NO - 2017 (Shift-1)

Explanation

This statement is incorrect because the Sinoatrial (SA) node, not the Atrioventricular (AV) node, is the primary pacemaker of the heart.
The SA node has the fastest intrinsic rate of depolarization (60-100 beats per minute), which sets the normal sinus rhythm.
The AV node functions as a secondary or backup pacemaker, taking over only if the SA node fails. Its intrinsic rate is significantly slower (40-60 beats per minute).

Option A: This is a correct statement. The SA node, the heart's natural pacemaker, is a cluster of specialized cells located in the upper part of the wall of the right atrium.
Option B: This is a correct statement. The AV node is a mass of neuromuscular tissue situated in the interatrial septum, close to the tricuspid valve.
Option D: This is a correct statement. The Bundle of His (or AV bundle) is a crucial part of the conduction pathway that originates from the AV node and transmits the electrical impulse to the ventricles.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Conduction System of the Heart as background academic context rather than a clinical decision trigger.
Understanding the heart's conduction system is fundamental for nurses, especially for interpreting electrocardiograms (ECGs) and identifying arrhythmias.
If the SA node fails (a condition known as sick sinus syndrome), the AV node may take over, resulting in a slower heart rate (bradycardia) called a junctional rhythm. Nurses must recognize this on an ECG as it can lead to decreased cardiac output and symptoms like dizziness or syncope.
What if a patient's ECG shows a heart rate of 35 bpm with no relationship between P waves and QRS complexes? This could indicate a third-degree (complete) heart block, where atrial impulses do not reach the ventricles at all. The ventricles are paced by an even slower escape rhythm from the Purkinje fibers. This is a medical emergency requiring immediate intervention, often with an external or permanent pacemaker.

How to Approach the Question

First, carefully read the question and note the keyword 'wrong statement'. This means you are looking for the one option that is factually incorrect.
Review your knowledge of the heart's electrical conduction system, including the roles and locations of the SA node, AV node, and Bundle of His.
Evaluate each option individually against this knowledge.
Option A describes the SA node's location. Verify if this is correct.
Option B describes the AV node's location. Verify if this is correct.
Option C makes a claim about the AV node's primary function. Compare this with the known primary pacemaker of the heart.

Concept Tested & Keywords

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

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

Practise the full AIIMS Raipur NO - 2017 (Shift-1)

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