ATI RN

1. Which heart chamber receives oxygenated blood from the four pulmonary veins and serves as a reservoir during ventricular systole?

• A. Right atrium
• B. Left atrium
• C. Right ventricle
• D. Left ventricle

Correct Answer: B

Rationale: The correct answer is B, Left atrium. The left atrium receives oxygenated blood from the lungs via the four pulmonary veins and acts as a holding chamber before the blood is pumped into the left ventricle. Choice A, Right atrium, is incorrect as it receives deoxygenated blood from the body via the vena cava. Choices C and D, Right ventricle and Left ventricle, are incorrect as they receive blood from the atria, not the pulmonary veins.

2. From where do these originate, behind the cusps of the aortic valve, in an area known as Valsalva’s sinus?

• A. Pulmonary valve
• B. Aortic valve
• C. Tricuspid valve
• D. Mitral valve

Correct Answer: B

Rationale: The correct answer is B, Aortic valve. The aortic valve is a semilunar valve located between the left ventricle and the aorta. It prevents the backflow of blood from the aorta into the left ventricle. The pulmonary valve (choice A) is located between the right ventricle and the pulmonary artery, not in the Valsalva’s sinus area. The tricuspid valve (choice C) is situated between the right atrium and right ventricle, and the mitral valve (choice D) is located between the left atrium and left ventricle, making them incorrect choices for this question.

3. Where is the impulse from the SA node delayed, enabling atrial contraction to complete before the ventricles are stimulated and contract?

• A. AV node
• B. Bundle of His
• C. SA node
• D. Aorta

Correct Answer: A

Rationale: The correct answer is AV node. The AV node is responsible for delaying the impulse from the SA node, allowing the atria to contract before the ventricles. This delay ensures the effective pumping of blood in a coordinated manner. Choices B, C, and D are incorrect because the Bundle of His is responsible for transmitting the impulse to the Purkinje fibers, the SA node is the pacemaker of the heart responsible for initiating the heartbeat, and the aorta is the main artery carrying oxygenated blood from the heart to the body, respectively, none of which are involved in delaying the impulse to allow atrial contraction before ventricular contraction.

4. What is the term that describes the inability of cardiac cells to respond to a new stimulus while they are still in contraction from a previous stimulus?

• A. Refractoriness
• B. Excitability
• C. Contractility
• D. Automaticity

Correct Answer: A

Rationale: Refractoriness is the correct term to describe the inability of cardiac cells to respond to a new stimulus while they are still in contraction from a previous stimulus. This period is essential for the heart to complete its contraction and relaxation phases without interference. Excitability refers to the ability of cells to respond to stimuli, not the inability to respond. Contractility is the force of cardiac muscle contraction, and automaticity is the ability of cardiac cells to generate electrical impulses spontaneously, which are not relevant to the described scenario.

5. What is the amount of tension the ventricle must develop during contraction to eject blood from the left ventricle into the aorta?

• A. Afterload
• B. Preload
• C. Automaticity
• D. Ejection fraction

Correct Answer: A

Rationale: Afterload is the correct answer because it refers to the pressure or tension that the ventricle must overcome during systole to eject blood into the aorta. Preload, on the other hand, is the degree of stretch of the ventricular muscle at the end of diastole before it contracts. Automaticity is the ability of the heart to generate electrical impulses independently, and ejection fraction is the percentage of blood pumped out of the ventricle with each heartbeat. Therefore, in the context of the question, afterload best describes the amount of tension the ventricle must develop to eject blood into the aorta.