Identify the three layers of the heart:

Correct Answer: A

Rationale: Rationale: 1. Endocardium: Innermost layer lining the heart chambers. 2. Myocardium: Middle layer composed of cardiac muscle tissue. 3. Epicardium: Outermost layer forming the visceral pericardium. Therefore, the correct answer is A. Summary: B is incorrect as it includes Pericardium instead of Myocardium. C is incorrect as it switches the positions of Myocardium and Epicardium. D is incorrect as it has the layers listed in the wrong order and includes Pericardium as the innermost layer.

Correct Answer: A

Rationale: The correct answer is A: Coronary perfusion pressure. Coronary perfusion pressure is the pressure gradient that drives blood flow through the coronary arteries into the myocardium during diastole when the coronary vascular resistance is reduced. This pressure gradient is essential for delivering oxygen and nutrients to the heart muscle when it is relaxed and filling with blood. During diastole, the coronary arteries receive blood flow predominantly due to the pressure difference between the aortic diastolic pressure and the pressure in the coronary vasculature. Summary of why the other choices are incorrect: B: Coronary vascular resistance - This factor is reduced during diastole, allowing for increased blood flow, but it does not directly drive blood flow to the myocardium. C: Diastolic filling - This refers to the filling of blood into the ventricles of the heart, not specifically the flow of blood through the coronary arteries. D: Ventricular ejection - This occurs during systole when the ventricles contract

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.