Cardiac Cycle

Cardiac Cycle - the sequence between two consecutive heartbeats, usually taking less than one second.

The cardiac cycle includes:

1. Systole, which is divided into periods:
   1. Isovolumetric contraction
   2. Exiles
2. Diastole, which includes periods:
   1. Isovolumetric relaxation
   2. Fillings

During simultaneous contraction of the atria, blood is ejected into the relaxed ventricles.

Then a powerful contraction of the ventricles occurs, which pumps blood into the aorta and pulmonary artery.

During ventricular contraction, the atria relax and fill with blood again.

See also:

1. Diastole
2. Systole

The heartbeat cycle is one of the most important processes in the human body. It ensures the continuous movement of blood through the circulatory system, ensuring its delivery to various organs and tissues.

The heartbeat cycle consists of two phases: systole and diastole. Systole is the contraction phase that begins when the ventricles of the heart fill with blood from the atria. At this time, the heart begins to contract, which leads to the release of blood into the aorta and lungs. Diastole is the relaxation phase that follows systole. During diastole, the ventricles fill with new blood from the atria, allowing them to prepare for the next contraction.

Systole consists of two periods: isovolumetric compression and expulsion. Isovolumetric contraction is a period when the ventricles contract but do not change volume. This occurs when the heart begins to contract the muscles. Expulsion is the period when the ventricular muscles contract and eject blood from the heart.

Diastole also consists of two periods: isovolumetric expansion and filling. Isovolumetric dilatation is the period when the ventricles relax and dilate. This happens before they fill with new blood. Filling is the period when blood enters the ventricles from the atria and fills them.

Thus, the heartbeat cycle plays an important role in maintaining human life. It allows the heart to pump blood throughout the body, delivering oxygen and nutrients to tissues and organs and removing carbon dioxide and other waste products.

**Cardiac cycle** or **cardiocycle** is one heartbeat, during which the heart pumps blood through the vessels and undergoes a relaxation process before the next active phase of contraction. Typically, the full stage of the cardiac cycle ends during the pause between the next two beats and takes only a few seconds.

Physiologists distinguish two main periods of heart contractions, accompanied by visible changes in both the heart and the circulatory system: diastole and systole. The human heart pumps approximately 6-7 liters of blood every hour. However, since such a large volume cannot be achieved in just one cardiac cycle, the heart periodically slows down and increases power only to fill its contractile function.

Diastole (systolic relaxation) occurs when the heart “relaxes” between two cardiac cycles. It begins at the moment of contraction of the ventricle, which has passed through the ejection phase and now restores the level of tension (diastole) that was used in this phase, while at this time the atrium is gradually and slowly filled with blood from the entire circulatory system. The next beat begins when the ventricle has fully recovered its Ca++ potential.

**Systole**, on the contrary, occurs during the “filling” of the cardiac canal, which is the site of active muscles. It consists of three stages: the isovolumetric phase, the ejection phase and the isovolumetric contraction phase. During isovolumetric muscle expansion, the body continues the systolic phase of diastole, trying to take the same shape as before the impact. This phase defines the first stage of rapid cardiac ejection of blood.

The ejection phase begins synchronously with the intracavitary cardiac wave. This causes a strong contraction