Chapter 13, Problem 7RQ

### Cardiopulmonary Anatomy & Physiolo...

7th Edition
Des Jardins + 1 other
ISBN: 9781337794909

Chapter
Section

### Cardiopulmonary Anatomy & Physiolo...

7th Edition
Des Jardins + 1 other
ISBN: 9781337794909
Textbook Problem

# The normal duration of the PR interval is no longer thanA. 0.12 secondB. 0.15 secondC. 0.20 secondD. 0.50 second

Summary Introduction

Introduction:

The heart is a pumping organ that pumps blood to different parts of the body by generating electrical impulses on its own. These electrical impulses generated in the heart are of major clinical significance and thus a system called electrocardiogram (ECG) is used to monitor the electrical activity of the heart. The ECG consists of waves, complexes, segments, and intervals that correspond to different activities of the heart such as the P wave, QRS complex, T wave, U wave, and QT interval. The ECG uses a characteristic graph paper having a square that denotes a particular time interval and this paper runs at the same speed as the ECG system.

Explanation

Justification/ Explanation for the correct answer:

Option (c) is 0.20 second. The normal duration of the PR interval can be no longer than 0.20 seconds. The PR interval is the measure of total electrical activity of the atria. It starts with the beginning of the P wave and ends at the start of the QRS complex. The interval corresponds to the atrial depolarization and other activities prior to activation of the bundle of His, ventricular branches and the Purkinje fiber system. The PR interval has a normal duration of 0.12 to 0.20 seconds. Hence, option (c) is correct.

The explanation for the incorrect answers:

Option (a) is 0.12 second. The normal duration of the PR interval is 0.12 to 0.20 seconds so it cannot be longer than 0.20 seconds. The waveform or the complex that is connected through a segment forms the interval...

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