How does the coronary artery supply affect the function of the heart's conduction system?
The circumflex artery supplies the atrioventricular node
The left anterior descending artery supplies the sinoatrial node
The left coronary artery supplies the sinoatrial node
The right coronary artery supplies the sinoatrial and atrioventricular nodes
The Correct Answer is D
A. The circumflex artery supplies the atrioventricular node:
In most individuals, the AV node is supplied by the right coronary artery, not the circumflex. The circumflex supplies the lateral and posterior walls of the left ventricle.
B. The left anterior descending artery supplies the sinoatrial node:
The LAD primarily supplies the anterior wall of the left ventricle and the interventricular septum, not the SA node.
C. The left coronary artery supplies the sinoatrial node:
The left coronary artery branches into the LAD and circumflex, which supply the left ventricle and parts of the atrium, but the SA node is usually supplied by the right coronary artery in about 60% of people.
D. The right coronary artery supplies the sinoatrial and atrioventricular nodes:
The RCA commonly supplies the SA node (~60% of people) and the AV node (~85% of people), which are crucial for initiating and coordinating the heartbeat. Occlusion of the RCA can cause arrhythmias or conduction blocks.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
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.
Correct Answer is C
Explanation
A. Coronary arteries are filled with blood during atrial contraction:
Coronary arteries are primarily perfused during diastole, not atrial contraction. During systole, contraction of the ventricles compresses the coronary vessels, reducing blood flow.
B. Coronary circulation occurs only during systole:
Coronary blood flow mostly occurs during diastole, because the myocardial contraction during systole compresses the coronary vessels, especially in the left ventricle.
C. Coronary veins return deoxygenated blood to the right atrium:
Coronary veins collect deoxygenated blood from the myocardium and empty it into the right atrium via the coronary sinus, completing the coronary circulation.
D. Coronary arteries supply deoxygenated blood to the heart muscle:
Coronary arteries supply oxygenated blood to the heart muscle, not deoxygenated blood.
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