What is the cardiac cycle?
The time during which the heart is at rest
The flow of blood through the body
The series of pressure changes that occur within the heart from the beginning of one heartbeat to the beginning of the next.
The electrical impulses of the heart
The Correct Answer is C
A. The time during which the heart is at rest: This describes diastole, a single phase of the cardiac cycle when the heart muscles relax and chambers fill with blood. While diastole is part of the cardiac cycle, it does not encompass the entire sequence of events from one heartbeat to the next.
B. The flow of blood through the body: This refers to systemic and pulmonary circulation, which are physiological processes involving blood movement but do not specifically define the cardiac cycle. The cardiac cycle is the sequence of mechanical and pressure events that drives this flow rather than the flow itself.
C. The series of pressure changes that occur within the heart from the beginning of one heartbeat to the beginning of the next: The cardiac cycle includes atrial and ventricular systole and diastole, with corresponding pressure and volume changes in all four chambers. These events coordinate valve opening and closing, blood ejection, and filling, ensuring efficient cardiac output with each heartbeat.
D. The electrical impulses of the heart: Electrical impulses, generated by the sinoatrial node and conducted through the conduction system, trigger the mechanical events of the cardiac cycle. While essential for initiating contraction, they represent only the electrical component and do not define the full sequence of pressure and volume changes that constitute the cardiac cycle.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is {"dropdown-group-1":"A","dropdown-group-2":"D"}
Explanation
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.
Correct Answer is ["B","C","D"]
Explanation
A. Increases vasodilation: The renin-angiotensin-aldosterone system (RAAS) primarily promotes vasoconstriction via angiotensin II to maintain perfusion pressure. It does not cause vasodilation; therefore, this is not a compensatory mechanism in heart failure.
B. Increased blood pressure: Activation of RAAS leads to angiotensin II–mediated vasoconstriction and aldosterone-mediated sodium retention, both of which increase systemic vascular resistance and blood pressure. This helps maintain perfusion to vital organs despite reduced cardiac output.
C. Increases heart rate: RAAS indirectly increases heart rate by promoting sympathetic nervous system activation. Elevated angiotensin II levels stimulate catecholamine release, contributing to tachycardia as a compensatory mechanism to maintain cardiac output.
D. Increases water retention: Aldosterone released by the adrenal cortex in response to RAAS activation enhances sodium and water reabsorption in the kidneys. This increases intravascular volume, which can help raise preload and temporarily improve stroke volume, though excessive retention may worsen edema.
E. Increases respirations: RAAS does not directly influence respiratory rate. Increased respirations in heart failure typically result from pulmonary congestion or hypoxia, not from RAAS activation.
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