What role does the AV node take on in a junctional dysrhythmia?
Pacemaker of the heart.
Defibrillator.
Takes on the role of the parasympathetic nervous system.
Takes on the role of the sympathetic nervous system.
The Correct Answer is A
Choice A rationale
In junctional dysrhythmias, the atrioventricular (AV) node assumes pacemaker activity when the sinoatrial node fails or impulses are blocked. The intrinsic firing rate of the AV junction is 40–60 beats/min. This rhythm ensures continued cardiac output despite primary pacemaker dysfunction. The impulse may travel retrograde to depolarize the atria and antegrade to the ventricles, resulting in inverted or absent P waves with normal QRS morphology on electrocardiography.
Choice B rationale
The AV node does not act as a defibrillator. Defibrillation delivers external electrical energy to depolarize all myocardial cells simultaneously, terminating lethal ventricular dysrhythmias. The AV node conducts physiologic impulses and cannot discharge electrical energy externally. Its function is impulse relay and backup pacemaking, not synchronized high-voltage energy delivery typical of defibrillation equipment used for cardiac arrest management.
Choice C rationale
The AV node does not replace parasympathetic nervous system function. Parasympathetic stimulation via the vagus nerve reduces heart rate by decreasing SA and AV nodal automaticity. The AV node’s role in junctional rhythms arises from intrinsic automaticity, not autonomic modulation. Although parasympathetic tone can influence AV conduction velocity, the node itself cannot substitute for neural parasympathetic activity controlling systemic heart rate and vascular tone balance.
Choice D rationale
The AV node does not assume sympathetic nervous system function. Sympathetic activation increases heart rate and conduction velocity via β1-adrenergic receptor stimulation. Junctional rhythms result from intrinsic pacemaker shift, not sympathetic compensation. Although sympathetic stimulation may accelerate junctional rate, it does not make the AV node a sympathetic structure. The node’s role is electrical impulse initiation and conduction rather than systemic neurohormonal regulation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A rationale
While establishing intravenous access is essential for medication administration and fluid therapy, particularly if the patient's condition deteriorates, it is not the absolute initial priority over diagnostic tests. Time is myocardium, and confirming the diagnosis via an ECG guides immediate life-saving interventions, making the ECG a faster, more critical first step. IV placement usually follows the ECG.
Choice B rationale
Pain assessment, though important for evaluation and subsequent treatment efficacy, should not precede the rapid diagnostic test (ECG) that confirms or rules out a critical, time-sensitive pathology like ST-elevation myocardial infarction (STEMI). The priority is rapid identification of ST-segment changes, which dictates immediate reperfusion therapy.
Choice C rationale
Administering aspirin is a crucial initial therapeutic intervention due to its antiplatelet effect, which inhibits thromboxane A2 and prevents further platelet aggregation at the site of coronary plaque rupture. However, the priority in the sequence of immediate care is obtaining the ECG to guide the type of reperfusion therapy needed, especially for STEMI.
Choice D rationale
Obtaining a 12-lead Electrocardiogram (ECG) is the single most critical and time-sensitive diagnostic intervention for chest pain concerning for acute myocardial infarction. The presence of ST-segment elevation dictates immediate reperfusion strategy (e.g., emergent cardiac catheterization or fibrinolysis), significantly impacting patient outcome and mortality. —.
Correct Answer is B
Explanation
Choice A rationale
Pulmonary crackles result from fluid accumulation in the alveoli, primarily associated with left-sided heart failure or mitral valve issues, where blood backs up from the left ventricle into the lungs. Tricuspid regurgitation (TR) affects the right side of the heart, causing systemic venous congestion rather than pulmonary edema.
Choice B rationale
Tricuspid regurgitation is the incomplete closure of the tricuspid valve, leading to a backflow of blood from the right ventricle into the right atrium during systole. This increases right atrial pressure and consequently the systemic venous pressure, which is clinically manifested as visible jugular venous distention (JVD) in the neck.
Choice C rationale
A left parasternal heave is an outward thrust palpable along the left sternal border, typically caused by right ventricular hypertrophy or dilation due to conditions like severe pulmonary hypertension. While TR can cause right ventricular dilation, the heave is a structural finding, whereas JVD is a direct sign of the acute volume backflow.
Choice D rationale
Absent peripheral pulses indicate severe peripheral vascular disease or critical limb ischemia, conditions unrelated to the primary pathophysiology of tricuspid regurgitation. While severe right heart failure can cause low cardiac output, it does not characteristically lead to absent peripheral pulses; dependent edema is more common. —.
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