The stretch before contraction correlates to?

The stretch before contraction correlates to?

• A. Pre-load
• B. After-load
• C. Contractility
• D. Heart rate

Answer: (A)

Stretch before contraction corresponds to preload. Preload is the initial stretch of the ventricular muscle fibers at the end of diastole, determined by venous return and filling volume. This stretch sets the sarcomere length and, via the Frank-Starling mechanism, a greater preload increases the force of contraction and stroke volume within physiological limits. The other terms describe different concepts: afterload is the pressure the ventricle must overcome to eject blood, contractility is the intrinsic ability of the myocardium to contract independent of stretch, and heart rate is how often the heart beats per minute.

Stretch before contraction corresponds to preload. Preload is the initial stretch of the ventricular muscle fibers at the end of diastole, determined by venous return and filling volume. This stretch sets the sarcomere length and, via the Frank-Starling mechanism, a greater preload increases the force of contraction and stroke volume within physiological limits. The other terms describe different concepts: afterload is the pressure the ventricle must overcome to eject blood, contractility is the intrinsic ability of the myocardium to contract independent of stretch, and heart rate is how often the heart beats per minute.