What is the ability of cardiac cells to generate an electrical impulse without being stimulated by an external source?

Correct Answer: A

Rationale: Automaticity is the ability of cardiac cells to generate an electrical impulse spontaneously without external stimulation. It is a fundamental property of specialized cardiac cells like pacemaker cells. Contractility refers to the ability of muscle cells to contract in response to an electrical stimulus. Conductivity is the ability of cardiac cells to transmit electrical impulses. Refractoriness is the period during which cardiac cells are unable to respond to a new stimulus. Therefore, in this context, the correct answer is A: Automaticity.

Correct Answer: A

Rationale: The correct answer is A: Angina. Angina is characterized by chest pain due to reduced blood flow to the heart muscle, often triggered by physical exertion or stress. It is typically relieved by rest or medication. Myocardial infarction (B) is a heart attack, which results from a complete blockage of blood flow to a part of the heart muscle. Pericarditis (C) is inflammation of the pericardium, the outer lining of the heart, causing sharp chest pain that worsens with breathing. Arrhythmia (D) refers to abnormal heart rhythms and may not necessarily present with chest pain due to reduced blood flow.

Correct Answer: A

Rationale: The correct answer is A: Ischemic stroke. This type of stroke is caused by a blockage in an artery supplying blood to the brain, leading to a lack of oxygen and nutrients to brain cells. This blockage can be due to a blood clot or plaque buildup. Ischemic strokes account for the majority of stroke cases. Incorrect choices: B: Hemorrhagic stroke - This type of stroke occurs when a blood vessel in the brain ruptures, leading to bleeding in the brain. C: Transient ischemic attack - Also known as a mini-stroke, it is caused by a temporary blockage of blood flow to the brain, often resolving on its own without permanent damage. D: Embolism - This refers to a condition where a blood clot or other foreign material travels through the bloodstream and blocks a blood vessel in the brain.

Correct Answer: A

Rationale: The correct answer is A: Paroxysmal nocturnal dyspnea. This condition is characterized by sudden, severe shortness of breath at night. It can be caused by heart failure or other cardiac conditions. Sleep apnea (B) is a disorder where breathing repeatedly stops and starts during sleep, not specifically related to acute shortness of breath. Orthopnea (C) is difficulty breathing while lying flat and is not specific to nighttime episodes. Dyspnea (D) is a general term for difficulty breathing and does not specifically refer to acute episodes at night.

Correct Answer: A

Rationale: Pulmonary edema is the correct answer because it is characterized by fluid accumulation in the lungs, leading to difficulty in breathing. This condition is often a result of heart failure, where the heart is unable to pump blood effectively, causing fluid to leak into the lungs. It can also be caused by lung infections or exposure to toxins. Pleurisy (B) is inflammation of the pleura, the lining around the lungs, leading to chest pain exacerbated by breathing. Pleural effusion (C) is fluid accumulation in the pleural space around the lungs, not within the lungs themselves. Pneumothorax (D) is characterized by air accumulation in the pleural space, causing lung collapse, but not fluid collection in the lungs.