What are the phases of cardiac activity? What happens in each of them?

There are three phases of cardiac activity: atrial contraction, ventricular contraction, and a pause when the atria and ventricles are simultaneously relaxed. At this time, the heart is resting. In one minute at rest, it is reduced approximately 60-70 times. The high efficiency of the heart is explained by the rhythmic alternation of work and rest of each of its departments. At the time of relaxation, the heart muscle restores its efficiency. The heart rate depends on the conditions in which the person is. During sleep, the heart contracts more slowly, and during physical work, contractions become more frequent.

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