Ventricular Systole

Definition

Ventricular systole is the contraction phase of the ventricles in the cardiac cycle, during which the ventricles pump blood out of the heart. It is a crucial component of the heart's pumping mechanism, responsible for the ejection of blood into the pulmonary and systemic circulatory systems.

5 Must Know Facts For Your Next Test

1. Ventricular systole is triggered by the depolarization of the ventricles, which causes the ventricular myocardium to contract.
2. During ventricular systole, the atrioventricular (AV) valves close, and the semilunar valves (aortic and pulmonary) open, allowing blood to be ejected from the ventricles.
3. The duration of ventricular systole is approximately 0.3 seconds, and it is followed by the relaxation phase of ventricular diastole.
4. The volume of blood ejected from the ventricles during systole is known as the stroke volume, which is a key determinant of cardiac output.
5. Factors that can influence the duration and strength of ventricular systole include heart rate, preload, afterload, and contractility of the ventricular myocardium.

Review Questions

• Describe the role of ventricular systole in the cardiac cycle.
  • Ventricular systole is the contraction phase of the ventricles, during which the ventricles pump blood out of the heart. It is a crucial component of the cardiac cycle, as it is responsible for the ejection of blood into the pulmonary and systemic circulatory systems. During ventricular systole, the atrioventricular (AV) valves close, and the semilunar valves (aortic and pulmonary) open, allowing blood to be pumped out of the ventricles. The volume of blood ejected during systole is known as the stroke volume, which is a key determinant of cardiac output.
• Explain how factors such as heart rate, preload, afterload, and contractility can influence the duration and strength of ventricular systole.
  • The duration and strength of ventricular systole can be influenced by various factors, including heart rate, preload, afterload, and contractility of the ventricular myocardium. An increased heart rate can shorten the duration of ventricular systole, as the heart needs to complete the cardiac cycle more quickly. Preload, or the volume of blood filling the ventricles before contraction, can affect the strength of ventricular contraction through the Frank-Starling mechanism. Afterload, or the resistance the ventricles must overcome to eject blood, can also influence the strength of ventricular systole. Additionally, the contractility of the ventricular myocardium, which can be affected by factors such as hormones and calcium levels, can directly impact the force and duration of ventricular systole.
• Analyze the relationship between ventricular systole, stroke volume, and cardiac output, and explain how changes in these parameters can affect the overall cardiovascular function.
  • Ventricular systole, stroke volume, and cardiac output are closely related and interdependent parameters that play a crucial role in cardiovascular function. During ventricular systole, the ventricles contract and eject a certain volume of blood, known as the stroke volume. The stroke volume, in turn, is a key determinant of cardiac output, which is the total volume of blood pumped by the heart per minute. Changes in any of these parameters can significantly affect the overall cardiovascular function. For example, an increase in heart rate during ventricular systole can lead to a higher cardiac output, as more blood is pumped per minute. Conversely, a decrease in ventricular contractility or an increase in afterload can reduce stroke volume and, consequently, cardiac output, which can impact the body's ability to meet its oxygen and nutrient demands. Understanding the relationships between ventricular systole, stroke volume, and cardiac output is essential for evaluating and managing various cardiovascular conditions.

Related terms

Cardiac Cycle: The complete sequence of events that occurs from the beginning of one heartbeat to the beginning of the next, including ventricular systole and diastole.

Ventricular Diastole: The relaxation phase of the ventricles, during which the ventricles fill with blood in preparation for the next contraction.

Stroke Volume: The volume of blood pumped out of the ventricles during each contraction, which is a key determinant of cardiac output.