What is the primary function of the atrioventricular (AV) valves in the heart?
To facilitate blood flow from ventricles to the lungs
To prevent blood from flowing into the coronary arteries
To regulate blood flow between the two ventricles
To prevent backflow of blood into the atria
The Correct Answer is D
A. To facilitate blood flow from ventricles to the lungs:
Blood flow to the lungs occurs via the pulmonic valve and pulmonary artery, not the AV valves.
B. To prevent blood from flowing into the coronary arteries:
Coronary arteries receive blood from the aortic sinuses, independent of AV valves. AV valves do not regulate coronary perfusion.
C. To regulate blood flow between the two ventricles:
Blood does not flow directly between ventricles. AV valves regulate flow from atria to ventricles, not between ventricles.
D. To prevent backflow of blood into the atria:
The mitral and tricuspid valves prevent backflow of blood into the atria during ventricular contraction (systole), ensuring unidirectional blood flow and efficient cardiac output.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. Parasympathetic nervous system:
The parasympathetic nervous system slows heart rate and promotes relaxation (rest-and-digest response). It decreases cardiac output and does not increase blood pressure during stress.
B. Somatic nervous system:
The somatic nervous system controls voluntary skeletal muscle movements, not autonomic regulation of blood pressure.
C. Central nervous system:
While the CNS (brain and spinal cord) integrates signals, it is not the primary effector. Blood pressure changes are mediated by the autonomic branches.
D. Sympathetic nervous system:
The sympathetic nervous system is responsible for the fight-or-flight response, increasing heart rate, contractility, and vasoconstriction. These actions increase cardiac output and systemic vascular resistance, raising blood pressure during stress.
Correct Answer is C
Explanation
A. S3:
S3 occurs during rapid ventricular filling in early diastole and may indicate volume overload or heart failure. It is not related to valve closure.
B. S1:
S1 corresponds to the closure of the atrioventricular (mitral and tricuspid) valves at the beginning of systole.
C. S2:
S2 occurs at the closure of the semilunar valves (aortic and pulmonic) at the end of systole, marking the onset of ventricular diastole. It is best heard at the base of the heart and is the normal “dub” sound.
D. S4:
S4 occurs during atrial contraction at the end of diastole and is associated with a stiff or hypertrophic ventricle. It is not a normal sound and does not correspond to semilunar valve closure.
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