Isovolumetric Contraction

Definition

Isovolumetric contraction is a phase of the cardiac cycle where the ventricles contract, but there is no change in ventricular volume. This occurs as the ventricles generate enough pressure to overcome the pressure in the aorta and pulmonary arteries, but the atrioventricular (AV) valves remain closed, preventing blood from entering or leaving the ventricles.

5 Must Know Facts For Your Next Test

1. Isovolumetric contraction occurs immediately after the ventricles have finished filling with blood during diastole.
2. During this phase, the ventricular pressure rises rapidly as the ventricles contract, but the AV valves remain closed, preventing any change in ventricular volume.
3. The purpose of isovolumetric contraction is to generate enough pressure in the ventricles to overcome the pressure in the aorta and pulmonary arteries, allowing the semilunar valves (aortic and pulmonary) to open and blood to be ejected from the ventricles.
4. Isovolumetric contraction is a crucial step in the cardiac cycle, as it ensures that the ventricles are fully primed and ready to effectively pump blood to the body and lungs.
5. The duration of isovolumetric contraction is typically around 0.05 to 0.1 seconds, and it is followed by the ventricular ejection phase of the cardiac cycle.

Review Questions

• Explain the purpose of the isovolumetric contraction phase in the cardiac cycle.
  • The purpose of the isovolumetric contraction phase is to generate enough pressure within the ventricles to overcome the pressure in the aorta and pulmonary arteries, allowing the semilunar valves to open and blood to be ejected from the ventricles. During this phase, the ventricular pressure rises rapidly, but the atrioventricular (AV) valves remain closed, preventing any change in ventricular volume. This ensures that the ventricles are fully primed and ready to effectively pump blood to the body and lungs during the subsequent ventricular ejection phase.
• Describe the sequence of events that occur during the isovolumetric contraction phase of the cardiac cycle.
  • During the isovolumetric contraction phase, the ventricles have just finished filling with blood during diastole. The ventricular myocardium then contracts, causing a rapid rise in ventricular pressure. However, the atrioventricular (AV) valves remain closed, preventing any change in ventricular volume. The purpose of this phase is to generate enough pressure within the ventricles to overcome the pressure in the aorta and pulmonary arteries, allowing the semilunar valves to open and blood to be ejected from the ventricles during the subsequent ventricular ejection phase of the cardiac cycle.
• Analyze the importance of the isovolumetric contraction phase in the overall efficiency of the cardiac cycle.
  • The isovolumetric contraction phase is a critical component of the cardiac cycle, as it ensures that the ventricles are fully primed and ready to effectively pump blood to the body and lungs. By generating a rapid rise in ventricular pressure without any change in volume, the ventricles are able to overcome the pressure in the aorta and pulmonary arteries, allowing the semilunar valves to open and blood to be ejected. This efficient transfer of blood is essential for maintaining adequate perfusion to the body's tissues and organs. If the isovolumetric contraction phase were disrupted or absent, the overall effectiveness of the cardiac cycle would be compromised, potentially leading to reduced cardiac output and impaired organ function.

Related terms

Cardiac Cycle: The series of events that occur during one complete heartbeat, including ventricular contraction and relaxation, as well as the opening and closing of the heart valves.

Ventricular Systole: The contraction phase of the ventricles, where the ventricles generate pressure to pump blood out of the heart.

Atrioventricular (AV) Valves: The valves located between the atria and ventricles, which ensure blood flows in the correct direction through the heart.