Nokea
Which structure serves as the normal pacemaker of the heart?
- A. SA node
- B. AV node
- C. Purkinje fibers
- D. Atria
Correct Answer: A
Rationale: The correct answer is A: SA node. The SA node is known as the natural pacemaker of the heart because it initiates the electrical impulses that regulate the heartbeat. It is located in the right atrium and generates the electrical signals that coordinate the heart's contractions. The other choices, B: AV node, C: Purkinje fibers, and D: Atria, do play roles in the heart's electrical conduction system, but they do not serve as the primary pacemaker. The AV node delays the electrical impulses, the Purkinje fibers distribute the impulses to the heart muscles, and the atria contract to pump blood into the ventricles. However, none of these structures serve as the primary pacemaker like the SA node does.
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What does the PR interval measure?
- A. Time it takes for the electrical impulse to travel from the atria to the ventricles
- B. Measurement of ventricular depolarization
- C. Duration of ventricular repolarization
- D. Segment representing the time between ventricular depolarization and repolarization
Correct Answer: A
Rationale: The PR interval measures the time it takes for the electrical signal to travel from the atria to the ventricles, reflecting atrial depolarization and the delay at the AV node before ventricular activation. Option A is correct as it accurately describes the PR interval. Option B is incorrect as the PR interval does not measure ventricular depolarization. Option C is incorrect as the PR interval does not represent ventricular repolarization. Option D is incorrect as it describes the QT interval, not the PR interval.
Which type of heart valve disease occurs when the mitral valve does not close properly, allowing blood to flow backward into the left atrium?
- A. Mitral regurgitation
- B. Aortic stenosis
- C. Tricuspid regurgitation
- D. Pulmonary hypertension
Correct Answer: A
Rationale: The correct answer is A: Mitral regurgitation. When the mitral valve does not close properly, it causes blood to flow backward into the left atrium during the heart's contraction phase. This condition is known as mitral regurgitation. Aortic stenosis (B) is narrowing of the aortic valve, not related to the mitral valve. Tricuspid regurgitation (C) involves the tricuspid valve, not the mitral valve. Pulmonary hypertension (D) is high blood pressure in the lungs, not directly related to a malfunctioning mitral valve.
What is a genetic disorder that affects the lungs and digestive system, leading to thick, sticky mucus that can clog the airways?
- A. Cystic fibrosis
- B. COPD
- C. Bronchiectasis
- D. Pulmonary fibrosis
Correct Answer: A
Rationale: The correct answer is A: Cystic fibrosis. Cystic fibrosis is a genetic disorder caused by mutations in the CFTR gene, leading to the production of thick mucus that affects the lungs and digestive system. This thick mucus can clog the airways, causing breathing difficulties and increasing the risk of lung infections. COPD (Choice B) is a different condition characterized by airflow obstruction usually due to smoking. Bronchiectasis (Choice C) is a condition where the airways are permanently widened and can also lead to mucus buildup but is not specific to the CFTR gene mutation. Pulmonary fibrosis (Choice D) is a lung disease characterized by scarring of lung tissue, not mucus buildup.
Which heart chamber receives venous blood returning to the heart via the superior and inferior vena cava?
- A. Right atrium
- B. Left atrium
- C. Right ventricle
- D. Left ventricle
Correct Answer: A
Rationale: The correct answer is A: Right atrium. The right atrium receives venous blood returning to the heart via the superior and inferior vena cava. Blood from the body enters the right atrium through the vena cavae, then flows into the right ventricle and eventually gets pumped to the lungs for oxygenation. Choices B, C, and D are incorrect because the left atrium receives oxygenated blood from the lungs, the right ventricle pumps blood to the lungs, and the left ventricle pumps oxygenated blood to the rest of the body.
What is a condition where the heart muscle becomes thickened without an obvious cause, leading to a reduction in the heart's ability to pump blood?
- A. Hypertrophic cardiomyopathy
- B. Dilated cardiomyopathy
- C. Restrictive cardiomyopathy
- D. Myocarditis
Correct Answer: A
Rationale: The correct answer is A: Hypertrophic cardiomyopathy. In this condition, the heart muscle becomes thickened, affecting the heart's ability to pump blood efficiently. This is due to genetic mutations causing the muscle cells to grow abnormally. This leads to poor relaxation and filling of the heart, impairing its pumping function.
B: Dilated cardiomyopathy involves the heart muscle becoming weak and stretched, leading to reduced pumping ability.
C: Restrictive cardiomyopathy involves the heart muscle becoming stiff and rigid, impairing its ability to fill with blood properly.
D: Myocarditis is inflammation of the heart muscle, typically caused by infections or autoimmune conditions, leading to temporary reduction in heart function.
Hence, the correct answer is A as it specifically describes the scenario of a thickened heart muscle without an obvious cause impacting the heart's pumping ability.