Stroke volume

Definition

Stroke volume is the amount of blood ejected from the left ventricle of the heart with each heartbeat. It plays a crucial role in determining cardiac output, which is vital during physical activity and exercise as the body’s demand for oxygen increases. Stroke volume is influenced by factors such as heart size, contractility, preload, and afterload, all of which are interconnected with cardiovascular physiology.

5 Must Know Facts For Your Next Test

1. Stroke volume can increase during exercise due to enhanced venous return and increased contractility of the heart.
2. The average stroke volume in a resting adult is about 70 mL per beat but can rise significantly during intense physical activity.
3. Factors such as hydration levels and body position can influence stroke volume; for example, lying down can increase venous return and therefore stroke volume.
4. Stroke volume is an essential component in calculating cardiac output, as it reflects the heart's efficiency in pumping blood.
5. In athletes, stroke volume is often higher due to an increased heart size and improved cardiovascular conditioning, allowing for better performance.

Review Questions

• How does stroke volume adapt during physical exercise to meet the body's increased demand for oxygen?
  • During physical exercise, stroke volume adapts through mechanisms like increased venous return and improved myocardial contractility. As physical activity intensifies, the muscles require more oxygen-rich blood. The heart responds by increasing stroke volume, thus enhancing cardiac output to supply sufficient blood flow to meet the metabolic demands of active tissues. This adaptation is crucial for sustaining prolonged physical activity.
• Evaluate the relationship between preload and stroke volume in terms of their physiological significance.
  • Preload refers to the stretch on the ventricular walls before contraction, primarily determined by the amount of blood returning to the heart. An increase in preload generally leads to an increase in stroke volume, following the Frank-Starling law of the heart, which states that the more the heart muscle is stretched (up to a point), the stronger its contraction will be. This relationship is physiologically significant because it ensures that an adequate amount of blood is ejected during each heartbeat to meet varying demands on circulation.
• Synthesize how understanding stroke volume contributes to assessing cardiovascular health and performance in different populations.
  • Understanding stroke volume is crucial for assessing cardiovascular health because it provides insights into heart function and efficiency. In athletes, a higher stroke volume indicates good cardiovascular conditioning and ability to sustain higher levels of activity. In clinical populations, such as those with heart disease or hypertension, measuring stroke volume can help identify dysfunctions or abnormalities in cardiac performance. By synthesizing data on stroke volume alongside other measures like heart rate and blood pressure, healthcare providers can gain a comprehensive view of an individual's cardiovascular status and tailor interventions effectively.

Related terms

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

Preload: The degree of stretch of the cardiac muscle fibers at the end of diastole, influencing stroke volume and cardiac output.

Afterload: The resistance that the left ventricle must overcome to eject blood during systole, affecting stroke volume and overall heart function.