Correct Answer: A

Rationale: Excitability is the correct term that describes the ability of cardiac cells to respond to an impulse by contracting. Excitability refers to the cell's ability to respond to stimuli and generate an action potential. Choice B, Contractility, is incorrect as it refers to the ability of cardiac cells to contract after receiving a stimulus, not the response to the impulse itself. Choice C, Rhythmicity, is incorrect as it pertains to the heart's ability to contract rhythmically without external stimulation. Choice D, Conductivity, is incorrect as it refers to the ability of cardiac cells to transmit an impulse from cell to cell, not the direct response to the impulse by contracting.

Correct Answer: A

Rationale: In this scenario, the nurse's priority action should be to hold the digoxin and notify the healthcare provider. A heart rate of 48 bpm is low, and digoxin, being a medication that can further decrease the heart rate, should be withheld. Administering the digoxin as ordered (Choice B) would not be appropriate in this situation as it can exacerbate bradycardia. Atropine (Choice C) is not the initial treatment for this scenario; holding the digoxin is the first action. Increasing the dose of digoxin (Choice D) would be contraindicated due to the client's bradycardia. Therefore, the correct action is to hold the digoxin and inform the healthcare provider for further guidance.

Correct Answer: A

Rationale: The correct answer is the SA node. The sinoatrial (SA) node is known as the natural pacemaker of the heart as it generates electrical impulses initiating each heartbeat. The SA node is located in the right atrium and sets the rhythm and rate of the heartbeat. The AV node (choice B) is responsible for delaying the electrical impulse to allow the atria to contract before the ventricles. Purkinje fibers (choice C) are specialized cardiac fibers responsible for the rapid conduction of impulses to the myocardial cells, and the atria (choice D) are the upper chambers of the heart involved in receiving blood from the veins.

Correct Answer: A

Rationale: The correct answer is an echocardiogram. An echocardiogram utilizes high-frequency sound waves (ultrasound) to create images of the heart, enabling doctors to evaluate its structure, function, and detect any abnormalities. MRI (Choice B) uses magnetic fields and radio waves to produce detailed images of the body's structures. CT scan (Choice C) combines X-rays and computer technology to create cross-sectional images of the body. X-ray (Choice D) uses electromagnetic radiation to produce images of the internal structures of the body, but it is not the most suitable for assessing the heart's structure and function.

Correct Answer: A

Rationale: Pneumonia is the correct answer because it is an acute respiratory infection that inflames the alveoli in one or both lungs, leading to the accumulation of fluid or pus. This condition presents with symptoms like cough, fever, and difficulty breathing. Bronchitis is the inflammation of the bronchial tubes, not the alveoli. Tuberculosis is a bacterial infection that primarily affects the lungs but does not always result in alveolar inflammation. Asthma is a chronic respiratory condition characterized by airway inflammation and narrowing, not alveolar inflammation.