Which valve opens during ventricular systole and closes during ventricular diastole?

Correct Answer: B

Rationale: During ventricular systole, the ventricles contract to pump blood out. The pulmonary valve opens to allow blood to be ejected from the right ventricle into the pulmonary artery, leading to the lungs. This prevents the backflow of blood into the right ventricle during ventricular diastole when the ventricles relax. The aortic valve opens during ventricular systole to allow blood to be ejected from the left ventricle into the aorta, not during ventricular diastole. The mitral valve and tricuspid valve control the flow of blood between the atria and ventricles, not during ventricular systole. Therefore, the correct answer is B (Pulmonary valve).

Correct Answer: C

Rationale: The correct answer is C: Conductivity. Cardiac cells have the ability to transmit impulses along cell membranes, allowing for the coordinated contraction of the heart. Conductivity refers to this specific property of cardiac cells to propagate electrical signals. Contractility (A) refers to the ability of cardiac muscle cells to generate force during contraction. Automaticity (B) refers to the ability of cardiac cells to spontaneously generate electrical impulses. Rhythmicity (D) refers to the regularity of these electrical impulses in the heart. Conductivity is the most relevant choice as it directly addresses the transmission of impulses along cell membranes in cardiac cells.

Correct Answer: A

Rationale: Rationale: 1. Preload refers to myocardial fiber stretch before contraction. 2. It is related to the volume of blood in ventricles at end of diastole. 3. Preload is determined by the amount of venous return to the heart. 4. It influences the force of contraction and stroke volume. 5. Afterload (B) is the resistance the heart must overcome to pump blood. 6. Contractility (C) is the intrinsic strength of the heart muscle. 7. Ejection fraction (D) is the percentage of blood ejected from ventricles. Summary: - Preload is correct as it specifically relates to fiber stretch and volume of blood. - Afterload, contractility, and ejection fraction do not directly relate to ventricular volume and venous return.

Correct Answer: A

Rationale: The correct answer is A: Baroreflex. The baroreflex is a physiological mechanism that helps regulate blood pressure by responding to changes in pressure. When blood pressure decreases, the baroreceptors detect this change and trigger a sympathetic nervous system (SNS) response, leading to increased heart rate, contractility, and vasoconstriction to raise blood pressure. Conversely, when blood pressure increases, the baroreceptors trigger a parasympathetic (vagal) response, resulting in decreased heart rate and vasodilation to lower blood pressure. Summary of other choices: B: Cheyne-Stokes breathing is a pattern of breathing characterized by periodic waxing and waning of tidal volume. C: Frank-Starling Law describes the relationship between preload and stroke volume, not the response to changes in blood pressure. D: Starling reflex is not a recognized physiological mechanism related to blood pressure regulation.

Correct Answer: A

Rationale: The correct answer is A: Cardiogenic shock. Cardiogenic shock is characterized by decreased cardiac output and tissue perfusion due to the heart's inability to pump effectively, leading to organ failure. This condition is a result of heart failure or myocardial infarction. Myocardial infarction (choice B) is a cause of cardiogenic shock, but not the specific condition described. Endocarditis (choice C) and pericarditis (choice D) do not directly result in decreased cardiac output and tissue perfusion leading to organ failure like cardiogenic shock does.