Question

The cardiac pacemaker in a patient fails to function normally. The doctor finds that an artificial pacemaker is to be grafted in him. It will likely be grafted at the site of
(a) Atrioventricular bundle
(b) Purkinje system
(c) Sinoatrial node
(d) Atrioventricular node

Answer 1

This bundle of neurons is present in the right atrium, and failure of this part causes irregular beating of hearts, improper flow of blood, and other cardiac issues. This involuntary myocardial structure generates electrical impulses.

Complete answer:
The cardiac pacemaker in a patient will be grafted at the site of the Sinoatrial node.
The Sinoatrial node is an advanced group of neurons present in the upper side of the atrium (right) in the heart. The Sinoatrial node is the pacemaker that is present naturally in the heart, which starts the heartbeat in humans. Due to the failure of the function of the sinoatrial node, patients often graft an artificial pacemaker in the heart.

Additional information:
- When the Sinoatrial node is damaged, it will start to transmit non- coordinated electrical impulses to the chambers of the heart, causing symptoms like improper heart rate, weakness, dizziness, and sudden falls by the unconscious.

- The artificial pacemaker will form these rhythmical electrical impulses. Hence they are implanted at the place of the Sinoatrial node to reproduce the function of the sinoatrial node and rhythmic system to aid in the regulation of heartbeat.
- Sound of heartbeat is represented by Lubb and Dub sound. Lubb sound is formed by the closing of atrioventricular valves and the closing of semilunar valves at the root of the pulmonary artery and aorta produces Dub sound
So, the correct answer is the Sinoatrial node.

Note:
- Muscle fibers are made of Microfibrils which in turn is composed of Sarcomeres, which is the reason for the basic functioning of muscle i.e muscle contraction.
- The heart wall consists of three layers, which are Epicardium (the outermost layer) myocardium (middle thick layer) and endocardium (innermost layer).
- Since the cardiac muscles are involuntary and are not controlled by the somatic nervous system, is the reason why we are not able to control the heartbeat- like controlling other muscles.