Stroke volume

Definition

Stroke volume is the amount of blood ejected by the heart's left ventricle during one contraction. This measurement is crucial as it reflects the efficiency of the heart in pumping blood and is influenced by factors such as the heart's chamber structure and the valves that regulate blood flow, as well as the phases of the cardiac cycle which dictate when and how much blood is pushed out with each heartbeat.

5 Must Know Facts For Your Next Test

1. Stroke volume can be affected by preload, afterload, and contractility, which are key factors in how well the heart functions during different physical states.
2. Normal stroke volume for a resting adult is typically between 60 to 100 milliliters per beat.
3. Increased physical activity can enhance stroke volume due to improved contractility and increased venous return.
4. Measuring stroke volume helps assess cardiac health; lower values may indicate heart failure or other cardiovascular issues.
5. An increase in stroke volume can lead to a corresponding decrease in heart rate for a constant cardiac output, allowing for more efficient heart function.

Review Questions

• How does stroke volume relate to the function of cardiac chambers and valves?
  • Stroke volume is directly tied to how well the heart's chambers, particularly the left ventricle, function along with the valves that control blood flow. The left ventricle must fill properly during diastole (when it relaxes) and then contract effectively during systole (when it pumps) to ensure an adequate stroke volume. If any of the valves are dysfunctional or if the chamber structure is impaired, it can affect how much blood is ejected, ultimately impacting overall cardiac performance.
• Discuss the relationship between stroke volume and different phases of the cardiac cycle.
  • Stroke volume is closely related to several phases of the cardiac cycle, particularly diastole and systole. During diastole, the ventricles fill with blood, establishing end-diastolic volume; this phase sets up how much blood will be available for ejection. Then during systole, contraction occurs and stroke volume is determined by how effectively the heart can push out this volume. Any alterations in these phases can significantly affect stroke volume and overall cardiac output.
• Evaluate how changes in preload might impact stroke volume and overall cardiovascular health.
  • Preload refers to the amount of blood in the ventricles before contraction, influencing stroke volume. An increase in preload usually results in a higher stroke volume due to better stretching and subsequent contraction of cardiac muscle fibers. However, excessively high preload can lead to overdistension of the heart, potentially causing issues like heart failure over time. Therefore, maintaining an optimal preload level is essential for efficient heart function and cardiovascular health.

Related terms

Cardiac Output: The total volume of blood pumped by the heart per minute, calculated as stroke volume multiplied by heart rate.

End-Diastolic Volume: The volume of blood in the ventricles at the end of diastole, which directly affects stroke volume; more blood typically results in a higher stroke volume.

Preload: The initial stretching of the cardiac muscle fibers prior to contraction, which influences stroke volume based on the volume of blood returning to the heart.