What class of antiarrhythmic drugs blocks potassium channels prolonging phase 3 of the action potential and slowing the rate and conduction of the heart?
I.
IV.
III.
II.
The Correct Answer is C
Choice A rationale
Class I antiarrhythmic drugs block sodium channels, affecting phase 0 of the action potential, not phase 3.
Choice B rationale
Class IV antiarrhythmic drugs block calcium channels, which affects phase 2 of the action potential and slows heart rate and conduction.
Choice C rationale
Class III antiarrhythmic drugs block potassium channels, prolonging phase 3 of the action potential. This results in a prolonged repolarization period, reducing the risk of arrhythmia.
Choice D rationale
Class II antiarrhythmic drugs are beta-blockers that primarily affect phase 4 of the action potential, reducing heart rate and conduction, but they do not block potassium channels.
Nursing Test Bank
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Related Questions
Correct Answer is B
Explanation
Choice A rationale
Beta-adrenergic blockers generally do not decrease urinary output. These drugs primarily act on the cardiovascular system by blocking beta-adrenergic receptors, which results in lowered heart rate and blood pressure. Their effects are less pronounced on the renal system unless specific agents with renal effects are used.
Choice B rationale
Beta-adrenergic blockers decrease the strength of heart muscle contraction (negative inotropic effect). By blocking beta receptors, they inhibit the stimulatory effects of catecholamines on the heart, reducing the force of myocardial contraction, which helps decrease oxygen demand and control angina symptoms.
Choice C rationale
Beta-adrenergic blockers typically decrease heart rate (negative chronotropic effect) rather than increase it. They inhibit beta-adrenergic receptors, which leads to a slower heart rate and can help manage conditions like angina by reducing myocardial oxygen consumption.
Choice D rationale
Beta-adrenergic blockers decrease oxygen consumption by reducing heart rate and the force of contraction. These effects lower myocardial oxygen demand, which is beneficial for patients with angina by preventing episodes triggered by increased oxygen needs.
Correct Answer is C
Explanation
Choice A rationale
Aleve (naproxen) is not recommended for children under 12 years old due to the risk of side effects such as gastrointestinal bleeding and kidney issues.
Choice B rationale
Motrin (ibuprofen) is commonly used for pain and inflammation in children but is not the best option for mild pain like that caused by an elbow injury.
Choice C rationale
Acetaminophen (Tylenol) is recommended for children experiencing mild to moderate pain, such as elbow pain, due to its safety profile and effectiveness.
Choice D rationale
Aspirin is not recommended for children due to the risk of Reye's syndrome, a rare but serious condition that can cause swelling in the liver and brain.
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