What causes blood to flow from the atria into the ventricles during diastole?
Higher pressure in the atria than in the veins
Contraction of the atria
Higher pressure in the veins than in the atria
Contraction of the ventricles
The Correct Answer is B
A. Higher pressure in the atria than in the veins: While venous return contributes to atrial filling, blood flow from the atria into the ventricles during diastole is primarily driven by pressure gradients between the atria and ventricles, not just between veins and atria. Venous pressure alone does not account for the efficient filling of the ventricles.
B. Contraction of the atria: During atrial systole, the atria contract, increasing atrial pressure above ventricular pressure. This pressure gradient forces blood through the open atrioventricular valves (tricuspid and mitral) into the ventricles, completing the final phase of ventricular filling known as the “atrial kick,” which contributes approximately 20–30% of ventricular end-diastolic volume.
C. Higher pressure in the veins than in the atria: Although venous pressure drives passive filling of the atria, the actual movement of blood into the ventricles requires the atria to generate pressure higher than that in the relaxed ventricles. Without atrial contraction, ventricular filling would rely solely on passive flow, which is less efficient.
D. Contraction of the ventricles: Ventricular contraction occurs during systole, when ventricular pressure rises above atrial pressure. This causes the atrioventricular valves to close, preventing backflow into the atria. Ventricular contraction does not facilitate blood flow from atria to ventricles; it actually temporarily halts it.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. Meditation and deep breathing exercises: Techniques such as meditation, mindfulness, and slow, deep diaphragmatic breathing activate the parasympathetic nervous system via the vagus nerve. This reduces sympathetic stimulation, lowers heart rate, decreases blood pressure, and promotes relaxation, counteracting the cardiovascular effects of acute and chronic stress.
B. Increased cortisol production: Cortisol is a stress hormone released by the adrenal cortex in response to sympathetic activation. Elevated cortisol levels during stress can increase heart rate and blood pressure, so increasing cortisol would exacerbate, not reduce, stress-related cardiovascular effects.
C. Rapid and shallow breathing: Hyperventilation or rapid shallow breathing typically occurs during stress or anxiety. It increases sympathetic activity, may cause tachycardia, and does not mitigate the physiological effects of stress on heart rate.
D. Ignoring emotional distress: Suppressing or ignoring stress does not engage mechanisms that reduce sympathetic activity. Chronic unaddressed stress can increase heart rate, elevate blood pressure, and contribute to cardiovascular strain over time.
Correct Answer is B
Explanation
N: Pulmonary valve- The pulmonary valve is a semilunar valve between the right ventricle and pulmonary artery. It prevents backflow into the ventricle during diastole, facilitating blood flow toward the lungs for oxygenation.
E: Fossa ovalis - The fossa ovalis is a shallow, thumb-sized depression located in the interatrial septum (the wall separating the right and left atria). In a developing fetus, the foramen ovale is an open "tunnel" that allows blood to bypass the lungs by flowing directly from the right atrium to the left atrium. Once a baby takes their first breath, the pressure changes in the heart cause a flap of tissue to close over this opening. Over time, it fuses shut, leaving behind the shallow indensee fossa ovalis.
O: chordae tendinae: Chordae tendineae are fibrous cords connecting the atrioventricular valve leaflets (mitral and tricuspid) to papillary muscles. They prevent valve prolapse during ventricular contraction, ensuring unidirectional blood flow.
J: Aortic arch- The aortic arch is the curved portion of the aorta that distributes oxygenated blood from the left ventricle to systemic arteries. It contains baroreceptors and helps regulate blood pressure.
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