Final answer:
The cardiac event that cycles the beginning of systole is atrial depolarization, resulting in atrial contraction followed by ventricular systole. This sequence is essential for the heart's efficient blood pumping. Each phase of the cardiac cycle, including atrial and ventricular systole and diastole, is carefully regulated and coordinated.
Step-by-step explanation:
The cardiac event that signals the beginning of systole, the contraction phase of the cardiac cycle, is the depolarization which leads to the contraction of the atria. This is represented by the P wave on an electrocardiogram (ECG). Atrial systole is followed by ventricular systole, where the ventricles pump blood into the arteries. It's important to understand that the atrial contraction contributes to the ventricular filling, making up the final 20-30 percent of filling, known as the "atrial kick." The process of systole and diastole is crucial for efficient blood pump mechanism of the heart.
Detailed overview of the cardiac cycle:
- Atrial systole begins with the SA node's electrical charge, causing atrial contraction, signified by the P wave on the ECG.
- Following the atrial systole, ventricular systole occurs when the electrical impulse reaches the ventricles causing them to contract and pump blood through the arteries.
- The cycle proceeds with atrial diastole and ventricular diastole when the chambers relax and fill with blood, completing one cardiac cycle.
The cardiac cycle includes these phases of activity, and the precise timing ensures that the heart works at its peak efficiency, coordinating the contraction and relaxation phases during the pumping of blood.