Final answer:
Starling's Law of the Heart states that the more stretched the heart fibers are at the beginning of the contraction, the more powerful the contraction will be. This mechanism is important in regulating cardiac output.
Step-by-step explanation:
Starling's Law of the Heart states that, within limits, the longer or more stretched the heart fibers are at the beginning of the contraction, the more powerful the contraction will be.
For example, when the ventricles of the heart fill with blood (preload), the muscle fibers are stretched, allowing for an increased force of contraction.
This mechanism is important in regulating cardiac output and ensuring an adequate supply of blood to meet the body's demands.