The left bundle branch supplies the
The Correct Answer is {"dropdown-group-1":"A","dropdown-group-2":"D"}
A. Left, right atrium: The atria are primarily supplied with electrical impulses from the sinoatrial node via the internodal pathways and Bachmann’s bundle for the left atrium. The bundle branches do not supply the atria; they are part of the ventricular conduction system.
B. Right, left: Reversing the order would incorrectly suggest that the right bundle branch supplies the left ventricle and the left bundle branch supplies the right ventricle. Anatomically, each bundle branch corresponds to the ipsilateral ventricle.
C. Right, left atrium: The bundle branches are ventricular conduction pathways and do not directly supply the atria. Atrial depolarization occurs independently via atrial conduction fibers and does not involve the left or right bundle branches.
D. Left, right: The left bundle branch travels down the interventricular septum to supply the left ventricle, including its septal and free wall myocardium, while the right bundle branch courses along the right side of the septum to supply the right ventricle. These branches ensure rapid, coordinated depolarization of the ventricles, facilitating synchronized ventricular contraction.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. The amount of blood ejected per heartbeat: The volume of blood ejected per beat is stroke volume, not afterload. Stroke volume depends on preload, contractility, and afterload, but it is a measure of output, not the resistance faced by the ventricles.
B. The resistance the ventricles must overcome to eject blood: Afterload refers to the pressure the ventricles must overcome to open the semilunar valves and eject blood into the aorta or pulmonary artery. Factors influencing afterload include systemic vascular resistance, arterial pressure, and vascular compliance, all of which affect ventricular workload and cardiac efficiency.
C. The strength of myocardial contraction: The intrinsic force generated by the myocardium is contractility, which is influenced by calcium availability, sympathetic stimulation, and myocardial health. While contractility interacts with afterload, it is not synonymous with it.
D. The volume of blood returning to the heart before contraction: The volume of blood filling the ventricles before contraction is preload (end-diastolic volume), which stretches the myocardial fibers and contributes to the Frank-Starling mechanism. Afterload, in contrast, is the opposing pressure during ejection.
Correct Answer is B
Explanation
Correct answer: False
Preload refers to the degree of stretch of the ventricular myocardial fibers at the end of diastole, just before ventricular contraction. It is influenced by the volume of blood returning to the heart (venous return) and the compliance of the ventricular walls. End-diastolic volume (EDV) is the actual volume of blood present in the ventricle at the end of diastole. While preload is closely related to EDV, it is a functional measure of myocardial fiber stretch rather than a direct measurement of blood volume. Thus, preload describes the mechanical tension on the myocardium, whereas EDV quantifies the volume of blood in the chamber.
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