Diastole

Definition

Diastole refers to the phase of the cardiac cycle when the heart muscles relax, allowing the chambers of the heart to fill with blood. During this period, both the atria and ventricles undergo relaxation, which is crucial for efficient blood flow and maintaining proper circulation throughout the body. The timing and coordination of diastole are essential for optimal function of the heart's chambers and valves, affecting systemic and pulmonary circulation.

5 Must Know Facts For Your Next Test

1. Diastole comprises two main phases: early diastole, when blood flows passively into the ventricles, and late diastole, where atrial contraction pushes additional blood into the ventricles.
2. During diastole, the pressure in the ventricles decreases, which allows the atrioventricular valves to open and fill the ventricles with blood.
3. The length of diastole can be affected by heart rate; a higher heart rate can shorten diastolic time, potentially compromising cardiac filling.
4. Proper diastolic function is crucial for maintaining stroke volume and overall cardiac output during physical activity or at rest.
5. Impaired diastolic function can lead to conditions like heart failure with preserved ejection fraction (HFpEF), where the heart struggles to fill properly.

Review Questions

• How does diastole contribute to effective cardiac output during various levels of physical activity?
  • Diastole is vital for effective cardiac output as it ensures that the ventricles fill adequately with blood before each contraction. During physical activity, as heart rate increases, the duration of diastole decreases. However, if diastolic filling is compromised due to a high heart rate or impaired ventricular relaxation, it can lead to decreased stroke volume and overall cardiac output. Therefore, optimal diastolic function is essential to meet the increased oxygen demands of active tissues.
• In what ways do atrioventricular valves facilitate proper blood flow during diastole?
  • Atrioventricular valves play a critical role during diastole by opening to allow blood to flow from the atria into the ventricles. As pressure in the atria rises above that in the relaxed ventricles, these valves open and permit passive filling. This one-way flow is essential for ensuring that blood does not backtrack into the atria once ventricular contraction occurs during systole. The integrity and function of these valves directly impact efficient cardiac filling and overall hemodynamics.
• Evaluate how disturbances in diastolic function might lead to heart failure with preserved ejection fraction (HFpEF) and discuss its implications.
  • Disturbances in diastolic function can significantly contribute to heart failure with preserved ejection fraction (HFpEF). In HFpEF, although systolic function remains intact with normal ejection fraction, impaired relaxation and increased stiffness of the ventricles lead to inadequate filling during diastole. This results in elevated pressures in the heart and pulmonary circulation, causing symptoms like shortness of breath and fatigue. Understanding this relationship highlights how essential proper diastolic mechanics are for preventing heart failure and managing patient outcomes.

Related terms

Systole: Systole is the phase of the cardiac cycle when the heart muscles contract, pumping blood out of the chambers into the arteries.

Atrioventricular Valves: These are valves located between the atria and ventricles, ensuring one-way blood flow from the atria to the ventricles during diastole.

Stroke Volume: Stroke volume is the amount of blood ejected by the ventricles during each contraction, influenced by how well the heart fills with blood during diastole.