   Chapter 13, Problem 8RQ

Chapter
Section
Textbook Problem

The normal duration of the QRS complex is less thanA. 0.01 secondB. 0.05 secondC. 0.12 secondD. 0.15 second

Summary Introduction

Introduction:

Electrocardiography is a technique by which electrical activity of the heart is recorded. This uses a standard 12-lead system which consists of positive and negative electrodes that measure the electrical activities of different regions of the heart. These activities are recorded on a graph which is called the electrocardiogram (ECG). The electrocardiogram consists of intervals, waveforms, segments, and baselines. The standard ECG contains the P wave, PR interval, QRS complex, T wave, U wave, QT interval, and ST segments. The QRS complex has a higher amplitude than the P wave and consists of three waveforms, which are Q wave, S wave, and R wave.

Explanation

Justification/ Explanation for the correct answer:

Option (c) is, ‘0.12 seconds.’ The QRS complex represents the depolarization of the ventricles. It is followed by the depolarization of atria, which is represented by the P wave. The QRS complex has a higher amplitude than the P wave because the ventricles consist of greater muscle mass and need more force to pump blood. The left ventricle has to pump blood to all the body parts, so it demands greater force. The QRS complex covers two and a half squares, so the duration is less than 0.12 seconds under normal conditions. The duration of the QRS complex, if exceeds, then it signifies abnormalities. Hence, option (c) is correct.

The explanation for the incorrect answers:

Option (a) is, ‘0.01 seconds.’ The normal duration of the QRS complex is less than 0.12 seconds and it represents the ventricular depolarization. The QRS complex has three separate waveforms, which are Q wave, R wave, and S wave...

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