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The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral and tricuspid heart valves. There are two atria in the human heart – the left atrium receives blood from the pulmonary circulation , and the right atrium receives blood from the venae cavae of the systemic circulation .
Diastole (at right) normally refers to atria and ventricles at relaxation and expansion together—while refilling with blood returning to the heart. Systole (left) typically refers to ventricular systole, during which the ventricles are pumping (or ejecting) blood out of the heart through the aorta and the pulmonary veins.
The atria are electrically isolated from the ventricles, connected only via the AV node which briefly delays the signal. Coordinated contraction of ventricular cells. The ventricles must maximize systolic pressure to force blood through the circulation, so all the ventricular cells must work together.
The heart has four valves, which separate its chambers. One valve lies between each atrium and ventricle, and one valve rests at the exit of each ventricle. [8] The valves between the atria and ventricles are called the atrioventricular valves. Between the right atrium and the right ventricle is the tricuspid valve.
Contraction of the atria follows depolarization, represented by the P wave of the ECG. As the atrial muscles contract from the superior portion of the atria toward the atrioventricular septum, pressure rises within the atria and blood is pumped into the ventricles through the open atrioventricular (tricuspid, and mitral or bicuspid) valves.
Atrioventricular block (AV block) is a type of heart block that occurs when the electrical signal traveling from the atria, or the upper chambers of the heart, to ventricles, or the lower chambers of the heart, is impaired.
The heart is a biological pump designed to move blood through the brain and body. It has four chambers: two "upper" chambers called the atria, and two "lower" chambers called the ventricles. Anatomically, the atria are more posterior to the ventricles, but for ease of understanding, are often drawn "above" them.
As diastole ends, the ventricles begin depolarizing and, while ventricular pressure starts to rise owing to contraction, the atrioventricular valves close in order to prevent backflow to the atria. At this stage, which corresponds to the R peak or the QRS complex seen on an ECG , the semilunar valves ( aortic and pulmonary valves) are also closed .