XVI. Read Text B. Translate it. Memorize the figures: Text C. The Cardiac Rhythm

One knows that during the diastole the atria and ventricles take in (принимают) the blood. It has been determined that during the systole the atria and the ventricles discharge out the blood. The diastole of the ventricles takes place during the systole of the atria, and the systole of the ventricles takes place during the diastole of the, atria. These functions of the atria and the ventricles compose the cardiac rhythm.

The cardiac cycle lasts 0.9 second. The contraction of the atria lasts 0.2" and that of the ventricles 0.3". When the atria contract the ventricles are at rest. The diastole or the period of rest of the cardiac muscle lasts 0.4".

So during one cardiac cycle the ventricles work 0.3" but rest 0.6". The period of contraction of the ventricles is longer than that of the atria and the systolic blood pressure is always Higher than the diastolic one. Such an interesting cardiac rhythm which enables the heart to rest longer than to work is very important for the blood circulation.

If the period of cardiac rest has become constantly shorter, the rate of heartbeat increases. Such an increased rate of heartbeat may affect [a'fekt] (поражает) the heart and produce different cardiac diseases.

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