Stroke volume - preload, sarcomere length and Frank -Starling law

• Sarcomere length affects muscle tension and the force of contraction. • Increased muscle stretch (increased sarcomere length) at the beginning of contraction increases tension produced during the contraction. • A more forceful contraction ejects more blood, thus increasing stroke volume. • The relationship between preload stretch and stroke volume is known as the Frank-Starling law of the heart. • The greater the preload, the greater the sarcomere stretch, the greater the stroke volume. • The Frank-Starling law has limits. When cardiac muscle is overstretched, increasing ventricular filling has no significant effect on stroke volume.

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