Which part of the heart's conduction system serves as the primary pacemaker?
Atrioventricular (AV) node
Sinoatrial (SA) node
Purkinje fibers
Bundle of His
Which part of the heart's conduction system serves as the primary pacemaker?
The Correct Answer is B
A. Atrioventricular (AV) node:
The AV node can act as a secondary pacemaker if the SA node fails, but its intrinsic rate (40-60 bpm) is slower than the SA node. Its primary role is delaying conduction to allow ventricular filling, not initiating the heartbeat.
B. Sinoatrial (SA) node:
The SA node, located in the right atrium near the superior vena cava, is the primary pacemaker of the heart. It initiates electrical impulses at a rate of 60-100 bpm, setting the rhythm for the entire heart. Dysfunction can lead to bradycardia or arrhythmias.
C. Purkinje fibers:
Purkinje fibers conduct impulses rapidly throughout the ventricles but do not serve as the primary pacemaker. They can act as a backup pacemaker at 20-40 bpm if higher centers fail.
D. Bundle of His:
The Bundle of His transmits impulses from the AV node to the ventricles. While it is part of the conduction system, it cannot independently set the heart rate under normal conditions.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. Capillaries:
Capillaries are the sites of nutrient and gas exchange and have very thin walls; they do not actively regulate blood pressure.
B. Elastic arteries:
Elastic arteries (e.g., aorta) maintain pressure by stretching and recoiling but are not the primary site of active vasoconstriction or vasodilation.
C. Arterioles:
Arterioles are the resistance vessels of the circulatory system. Their smooth muscle can constrict or dilate in response to neural, hormonal, and local chemical signals, directly regulating blood pressure and blood flow to tissues.
D. Veins:
Veins act as capacitance vessels and have some smooth muscle, but their role in blood pressure regulation is limited compared to arterioles.
Correct Answer is C
Explanation
A. It supplies oxygenated blood to the heart:
The coronary sinus does not supply blood; this is the role of coronary arteries.
B. It supplies the interventricular septum with oxygenated blood:
The interventricular septum is supplied mainly by the left anterior descending artery, not the coronary sinus.
C. It drains deoxygenated blood from the myocardium:
The coronary sinus collects deoxygenated blood from the cardiac veins and empties it into the right atrium, completing the venous return from the myocardium. This is essential for maintaining myocardial oxygen balance.
D. It regulates coronary blood flow:
Coronary blood flow is regulated by autonomic control and local metabolic demand, not by the coronary sinus.
Whether you are a student looking to ace your exams or a practicing nurse seeking to enhance your expertise , our nursing education contents will empower you with the confidence and competence to make a difference in the lives of patients and become a respected leader in the healthcare field.
Visit Naxlex, invest in your future and unlock endless possibilities with our unparalleled nursing education contents today
Report Wrong Answer on the Current Question
Do you disagree with the answer? If yes, what is your expected answer? Explain.
Kindly be descriptive with the issue you are facing.