Which of the following statements correctly describes the Frank-Starling law of the heart?
A)The shorter the initial length of the cardiac muscle fibres prior to contraction, the more forceful will be the subsequent contraction because the fibres are already partially contracted.
B)Increasing the venous return increases the end-diastolic volume, which leads to an increased stroke volume, so the heart normally pumps out all the blood returned to it.
C) As cardiac output is reduced, blood pools in the vasculature so that arterial blood pressure increases.
D) The output of the left side of the heart must always exceed that of the right side of the heart because the right side pumps blood only to the lungs, whereas the left side must pump blood to the rest of the body.

Question

Quizplus · Accepted Answer

The Frank-Starling law of the heart states that within physiological limits, the greater the venous return, the greater the end-diastolic volume, and thus the greater the stroke volume. This is because as the heart fills with more blood during diastole, the increased stretch on the cardiac muscle fibers results in a stronger contraction during systole. Therefore, option B correctly describes the Frank-Starling law. Option A is incorrect because an increase in the initial length of cardiac muscle fibers would actually result in a weaker subsequent contraction. Option C is incorrect because reduced cardiac output would not cause blood pooling and an increase in arterial blood pressure - this is actually the opposite of what would occur. Option D is incorrect because the outputs of the left and right sides of the heart must be equal in order for blood to be properly circulated.

Which of the Following Statements Correctly Describes the Frank-Starling Law