What is the primary consequence of increasing ventricular muscle stretch within physiological limits?
Weaker contractions
Enhanced force of contraction
Reduced stroke volume
Decreased venous return
The Correct Answer is B
A. Weaker contractions: Within normal physiological limits, increasing ventricular stretch does not weaken contractions. Weak contractions may occur only if the muscle is overstretched beyond its optimal sarcomere length, which exceeds the Frank-Starling range.
B. Enhanced force of contraction: The Frank-Starling law of the heart states that increased ventricular filling stretches myocardial fibers, optimizing actin-myosin overlap within sarcomeres. This enhanced sarcomere alignment increases the force of contraction during systole, allowing the heart to eject a greater stroke volume in response to increased venous return.
C. Reduced stroke volume: Increasing ventricular preload within physiological limits actually increases stroke volume by enhancing contractile force. Stroke volume only decreases if the heart is overfilled beyond its optimal sarcomere length, leading to inefficient contraction.
D. Decreased venous return: Increasing ventricular stretch is a response to increased venous return, not a cause of decreased return. Venous return drives end-diastolic volume, which in turn stretches the ventricular muscle to regulate stroke volume according to the Frank-Starling mechanism.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is {"dropdown-group-1":"D"}
Explanation
A. Rate: The rate of contraction refers to the heart rate, which is determined by the frequency of action potentials generated by the sinoatrial node. While rate influences cardiac output, it does not describe the intrinsic strength of myocardial contraction.
B. Frequency: Frequency also relates to how often the heart beats over a period of time, essentially the number of cardiac cycles per minute. It does not reflect the force generated by the myocardial fibers during systole.
C. Speed: Speed could be interpreted as the velocity of contraction or conduction, but it does not measure the intrinsic strength of the ventricular contraction. Contractility is independent of how quickly the contraction occurs.
D. Force: Contractility refers to the inherent ability of cardiac muscle fibers to generate force during systole, independent of preload and afterload. It reflects the efficiency of actin-myosin cross-bridge formation and calcium handling within the myocardium, determining how strongly the heart can pump blood with each beat.
Correct Answer is D
Explanation
A. Blood is returned to the left side of the heart via the pulmonary veins.: The pulmonary veins are located posteriorly and return oxygenated blood from the lungs to the left atrium. From the left atrium, blood flows through the mitral (bicuspid) valve into the left ventricle during ventricular diastole. This describes normal anatomic blood flow into the left side of the heart.
B. The left ventricle contracts to push blood through the aortic semilunar valve.: The left ventricle forms the apex of the heart and has the thickest myocardial wall due to its role in systemic circulation. During left ventricular systole, it generates high pressure to open the aortic semilunar valve and eject blood into the ascending aorta.
C. The left ventricle fills after the blood passes through the bicuspid.: The bicuspid valve, also called the mitral valve, is located between the left atrium and left ventricle. During ventricular diastole, blood flows from the left atrium through this valve into the left ventricle. Proper opening of the mitral valve allows adequate ventricular preload before systole.
D. Blood in the left ventricle is deoxygenated.: The left ventricle receives oxygenated blood from the lungs via the left atrium and pulmonary veins. Its physiologic function is to pump oxygen-rich blood into the systemic circulation through the aorta. Deoxygenated blood is found on the right side of the heart, not within the left ventricular chamber.
Whether you are a student looking to ace your exams or a practicing nurse seeking to enhance your expertise , our nursing education contents will empower you with the confidence and competence to make a difference in the lives of patients and become a respected leader in the healthcare field.
Visit Naxlex, invest in your future and unlock endless possibilities with our unparalleled nursing education contents today
Report Wrong Answer on the Current Question
Do you disagree with the answer? If yes, what is your expected answer? Explain.
Kindly be descriptive with the issue you are facing.