Which structure serves as the major chemoreceptor of the heart?

Correct Answer: A

Rationale: The correct answer is A: Carotid body. The carotid body is the major chemoreceptor of the heart, detecting changes in oxygen levels in the blood. It sends signals via the glossopharyngeal nerve to regulate heart rate and blood pressure. The aortic body primarily monitors blood pressure, not chemoreception. The vagus nerve plays a role in regulating heart rate but is not a chemoreceptor. The SA node is the pacemaker of the heart, responsible for initiating the electrical signals for heart contraction, not chemoreception. Therefore, the carotid body is the correct choice for the major chemoreceptor of the heart.

Correct Answer: A

Rationale: The correct answer is A: Purkinje fibers. Purkinje fibers are specialized cardiac muscle fibers that distribute the electrical impulse from the AV node to the ventricles, causing them to contract. They are located in the ventricles and ensure synchronized and efficient contraction. The SA node (B) is the pacemaker of the heart, initiating the electrical impulse. The AV node (C) delays the impulse to allow for atrial contraction before ventricular contraction. The Bundle of His (D) is a pathway for the electrical impulse from the AV node to the bundle branches, which then lead to the Purkinje fibers for ventricular contraction.

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.