Chapter 45, Problem 1PL

The _______ of the conduction system is known as the pacemaker.
a. SA node
b. AV node
c. AV bundle
d. left bundle branch

Summary Introduction

Introduction: 

In animals, the heart is a muscular organ which pumps blood via circulatory system throughout the body. Blood gives oxygen and nutrients to the body, and removes metabolic wastes. The heart is placed just behind and moderately left of the sternum (breastbone) in humans.

In humans, birds and some other mammals, the heart is partitioned into four chambers: the upper right and left atria and the lower right and left ventricle.

A pacemaker is a medical machine that is situated at the top of the heart's right atrium to help control abnormal (or unusual) heart rates. This machine utilizes electrical pulses to imply the heart to beat (or vibrate) at a normal rate. The pacemaker is used to treat arrhythmias. Arrhythmias are the problem with the rhythm or rate of the heartbeat.

Answer to Problem 1PL

Correct answer: 

The correct answer is option (a) SA node.

Explanation of Solution

Explanation/justification for the correct answer: 

Option (a) SA node. The natural pacemaker of the heart is SA node. These cells can produce electrical impulses spontaneously. The chief function of a sinoatrial (SA) node cell is to begin the action potential of the heart so that it can pass through the whole heart and provoke contraction. So, this is the correct option.

Explanation for incorrect answer: 

Option (b) AV node. The tricuspid valve and the mitral valve are identified as the atrioventricular (AV) valve and attach the atrium to the ventricle. Both valves are positioned between the upper chambers (atria) and lower chambers (ventricles) and prevent the backflow of the blood from the ventricles into the atria during systole. So, this is an incorrect option.

Option (c) AV bundle. A bundle of specialized muscle fibers controls the heartbeat by conducting impulses from the right atrium of the ventricle is known as the AV bundle. AV bundle also termed as bundle of His. It transmits impulses from the ventricular note to the ventricles of the heart. So, this is an incorrect option.

Option (d) left bundle branch. The left bundle branch carries electrical signals to the bottom of the heart and causes the ventricles to beat. So, this is an incorrect option.

Conclusion

The SA node of the conduction system is known as the pacemaker. Hence, the correct answer is option (a) SA node.