Cardiovascular System Exam

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: Paroxysmal nocturnal dyspnea is the correct answer. It is characterized by sudden episodes of severe shortness of breath during sleep, often waking the individual. Choice B, Sleep apnea, involves pauses in breathing during sleep but does not usually present with acute shortness of breath. Choice C, Orthopnea, refers to shortness of breath that occurs when lying flat and is relieved by sitting up. Choice D, Dyspnea, is a general term for difficult or labored breathing and does not specifically describe acute episodes at night.

Correct Answer: A

Rationale: The correct answer is A, Pulmonary edema. Pulmonary edema is a condition where fluid accumulates in the air sacs of the lungs, causing breathing difficulty. Pleurisy (choice B) is inflammation of the pleura causing chest pain. Pleural effusion (choice C) is the buildup of excess fluid in the pleural space, the area between the layers of tissue that line the lungs and chest cavity. Pneumothorax (choice D) is the presence of air in the pleural space, which can cause a lung to collapse.

Correct Answer: A

Rationale: Pleural effusion is the correct answer as it refers to the accumulation of excess fluid between the layers of the pleura surrounding the lungs and chest cavity. This condition can be caused by various factors such as infections, heart failure, or cancer. Pulmonary edema (choice B) involves fluid accumulation in the lungs' air sacs and is not specific to the pleura. Atelectasis (choice C) is the collapse or closure of a lung leading to airless lung tissue and is not related to fluid buildup. Sarcoidosis (choice D) is a condition characterized by the growth of tiny collections of inflammatory cells in different parts of the body, not specifically involving fluid accumulation in the pleural space.

Correct Answer: A

Rationale: Mitral regurgitation is the correct answer. It occurs when the mitral valve does not close properly, allowing blood to flow backward into the left atrium. This condition can lead to symptoms such as fatigue, shortness of breath, and if left untreated, it can progress to heart failure. Aortic stenosis (choice B) is a different heart valve condition characterized by narrowing of the aortic valve, restricting blood flow from the heart. Tricuspid regurgitation (choice C) involves the tricuspid valve not closing properly, leading to blood flowing back into the right atrium. Pulmonary hypertension (choice D) is a condition characterized by high blood pressure in the arteries of the lungs.