Frank-Starling Law

Definition

The Frank-Starling law, also known as the Frank-Starling mechanism, is a fundamental principle that describes the relationship between the volume of blood entering the heart (preload) and the force of contraction of the heart's ventricles. It explains how the heart can automatically adjust its output to meet the body's changing demands for blood flow.

5 Must Know Facts For Your Next Test

1. The Frank-Starling law states that the greater the preload (the volume of blood filling the ventricles), the greater the force of contraction and the volume of blood pumped out by the ventricles (stroke volume).
2. This mechanism allows the heart to automatically adjust its output to meet the body's changing demands for blood flow and oxygen delivery.
3. Increased preload stretches the cardiac muscle fibers, which triggers the release of more calcium ions and results in a stronger contraction.
4. The Frank-Starling mechanism is an important autoregulatory process that helps maintain cardiac output and blood pressure during changes in venous return or afterload.
5. Impairment of the Frank-Starling mechanism can contribute to the development of heart failure, where the heart is unable to adequately increase its output to meet the body's needs.

Review Questions

• Explain how the Frank-Starling law relates to the cardiac muscle tissue and its ability to contract.
  • The Frank-Starling law describes the relationship between the volume of blood entering the heart (preload) and the force of contraction of the heart's ventricles. Increased preload stretches the cardiac muscle fibers, which triggers the release of more calcium ions and results in a stronger contraction. This mechanism allows the heart to automatically adjust its output to meet the body's changing demands for blood flow and oxygen delivery, which is a crucial function of the cardiac muscle tissue.
• Discuss how the Frank-Starling law influences the cardiac cycle and the electrical activity of cardiac muscle.
  • The Frank-Starling mechanism is an important autoregulatory process that helps maintain cardiac output and blood pressure during changes in venous return or afterload. As the ventricles fill with more blood (increased preload), the cardiac muscle fibers stretch, leading to a stronger contraction and increased stroke volume. This directly affects the electrical activity of the cardiac muscle, as the increased calcium release and muscle fiber stretching influence the action potentials and the timing of the cardiac cycle. The Frank-Starling law, therefore, plays a crucial role in the coordination of the electrical and mechanical events that occur during the cardiac cycle.
• Analyze how impairment of the Frank-Starling mechanism can contribute to the development of heart failure and its impact on the cardiovascular system.
  • Impairment of the Frank-Starling mechanism can contribute to the development of heart failure, where the heart is unable to adequately increase its output to meet the body's needs. When the heart is unable to respond to increased preload by increasing the force of contraction, it can lead to a decrease in stroke volume and cardiac output. This can result in a cascade of events, including reduced blood flow to the body's tissues, increased venous pressure, and the potential for fluid buildup in the lungs or other organs. The inability of the heart to effectively utilize the Frank-Starling mechanism is a key factor in the pathophysiology of heart failure, as it compromises the heart's ability to adapt to changing cardiovascular demands and maintain proper circulatory function.

Related terms

Preload:

The amount of blood filling the ventricles of the heart prior to contraction, which stretches the cardiac muscle fibers and influences the force of contraction.

Contractility:

The intrinsic ability of the cardiac muscle to contract with a certain force, independent of preload or afterload.

Afterload:

The resistance the ventricles must overcome to eject blood, primarily determined by the pressure in the aorta and pulmonary arteries.