By what mechanism does an increase in venous return lead to an increase in stroke volume during the cardiac cycle?

• A. Frank-Starling mechanism
• B. Baroreceptor reflex
• C. Bainbridge reflex
• D. Chemoreceptor response

Answer: (A)

Verified step by step guidance

1. Understand the concept of venous return: Venous return is the flow of blood back to the heart. An increase in venous return means more blood is returning to the heart, particularly to the right atrium.
2. Learn about the Frank-Starling mechanism: This principle states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (the end diastolic volume) when all other factors remain constant.
3. Explore how the Frank-Starling mechanism works: As more blood returns to the heart, the cardiac muscle fibers are stretched more. This stretching leads to a more forceful contraction, which increases the stroke volume.
4. Differentiate from other mechanisms: The baroreceptor reflex, Bainbridge reflex, and chemoreceptor response are different physiological responses. The baroreceptor reflex helps regulate blood pressure, the Bainbridge reflex responds to changes in blood volume, and the chemoreceptor response is related to changes in blood chemistry.
5. Conclude with the correct mechanism: The increase in stroke volume due to increased venous return is primarily explained by the Frank-Starling mechanism, as it directly relates to the heart's ability to adjust its force of contraction based on the volume of blood it receives.