Chapter 19, Problem 1TYR

The cardiac conduction system includes all of the following except

1. a. tlie SA node.
2. b. the AV node.
3. c. the bundle blanches.
4. d. the tendinous cords.
5. e. the subendocardial conducting network.

Summary Introduction

Introduction:

Heartbeat is an autonomous involuntary action. Even though it is an involuntary action, heartbeat initiation and conduction is solely controlled by the heart itself, irrespective of the central autonomic control from the nervous system.  Heartbeat is initiated by the sinoatrial node, the pacemaker of the heart. From the SA node, it passes through a series of conduction system like atrioventricular node (AV) node, bundle of his, and finally by the sub-endocardial conducting network, so called as the Purkinje fibers. This is the general heart conduction pathway.

Answer to Problem 1TYR

Correct answer:

The cardiac conduction system includes all the following components, except the tendinous cords. Therefore, option d is correct.

Explanation of Solution

Justify reasons for the correct statement:

Tendinous cords are the heart strings that connect the papillary muscles with the atrioventricular valves (bicuspid and tricuspid valves) of the heart. These tendinous cords are responsible for preventing the valves from getting prolapse during heart beat contraction and relaxation.

Option (d) is given as “tendinous cords”.

Tendinous cord is not a part of heartbeat conduction system.

Hence, option (d) is correct.

Justify reasons for the incorrect statements:

Option (a) is given as “the SA node”.

SA node so called as the sinoatrial node is the pacemaker of the heart. It is the prime nodal center in the heart beat initiation from where the heartbeat is originated. Hence, it is wrong answer.

Option (b) is given as “the AV node”.

AV node so called as atrioventricular node is just beneath the SA node in the junction of atrium and ventricular fusion. The heartbeat initiation pulse started from the SA node travels to the AV node immediately. Hence it is wrong answer.

Option (c) is given as “the bundle of branches”.

Bundle of branches or otherwise called as bundle of his is the third prominent nodal center in receiving the heartbeat conduction impulse originated from SA node to AV node. Hence it is the wrong answer.

Option (e) is given as “the sub-endocardial conducting network”.

Sub-endocardial network, so called as the Purkinje fibers, which is a network of fibers supplied in the walls of ventricles. The heartbeat initiation command impulse originated from SA node and travel to AV node and through bundle of his and finally it reaches the Purkinje fibers, whereby it passes the signal to the entire heart muscles. Hence, it is the wrong answer.

Hence, options (a), (b), (c), and (e) are incorrect.

Conclusion

Tendinous cord is a heart string that connects the papillary muscles with that of atrioventricular valves, which help them to open and close better without any prolapse.