Systole

Definition

Systole is the phase of the cardiac cycle during which the heart muscles contract, pumping blood out of the chambers. This contraction is crucial for maintaining blood flow throughout the body and is directly linked to the function of the cardiac chambers and valves, as well as the heart's electrical activity. Understanding systole is key to comprehending how blood is circulated through both systemic and pulmonary pathways.

5 Must Know Facts For Your Next Test

1. Systole occurs in both the atria and ventricles, with atrial systole happening first to fill the ventricles before ventricular systole pumps blood to the lungs and body.
2. During systole, the pressure in the ventricles rises sharply as they contract, forcing the atrioventricular valves to close and preventing backflow into the atria.
3. The duration of systole varies based on heart rate; a faster heart rate results in a shorter systolic phase.
4. Systolic blood pressure is measured during this contraction phase and is an important indicator of cardiovascular health.
5. Abnormalities in systolic function can lead to conditions such as heart failure, where the heart cannot effectively pump blood during this critical phase.

Review Questions

• How does systole contribute to effective blood circulation within the body?
  • Systole plays a vital role in blood circulation by ensuring that the heart pumps blood effectively into both systemic and pulmonary circulation. During ventricular systole, the contractions increase pressure within the ventricles, allowing blood to be pushed into the aorta and pulmonary artery. This action not only delivers oxygenated blood throughout the body but also removes carbon dioxide from deoxygenated blood returning from systemic circulation.
• What are the physiological changes that occur during systole in relation to cardiac valves?
  • During systole, when the ventricles contract, ventricular pressure rises significantly. This pressure causes the atrioventricular (AV) valves (the mitral and tricuspid valves) to close, preventing backflow into the atria. At the same time, this pressure opens the semilunar valves (the aortic and pulmonary valves), allowing blood to exit the heart and enter into systemic or pulmonary circulation. The precise coordination of these events ensures efficient flow and prevents regurgitation.
• Evaluate how abnormalities in systolic function can lead to cardiovascular diseases and their implications.
  • Abnormalities in systolic function can manifest as reduced contractility or impaired relaxation of heart muscle, leading to conditions such as heart failure or cardiomyopathy. When systole is compromised, it can result in inadequate cardiac output, causing symptoms like fatigue and shortness of breath. Over time, these dysfunctions contribute to increased pressures within the heart chambers, potentially leading to further complications such as arrhythmias or elevated risk for myocardial infarction, significantly impacting overall cardiovascular health.

Related terms

Diastole:

The phase of the cardiac cycle when the heart muscles relax, allowing the chambers to fill with blood.

Cardiac Output: The volume of blood pumped by the heart per minute, which is influenced by heart rate and stroke volume during systole.

Electrocardiogram (ECG): A test that measures the electrical activity of the heart, showing the timing of systole and diastole.