Annual deaths from tornadoes, earthquakes and floods together total fewer than 200. The most deadly heat wave in recent years occurred in Chicago over a week in July 1995, when temperatures hovered around 100 degrees.
Cardiac Cycle: 1st Systole Phase. During the systole phase, the right ventricle receives impulses from the Purkinje fibers and contracts. The atrioventricular valves close and the semilunar valves open. The de-oxygenated blood is pumped into the pulmonary artery.
Systole is the last stage of a heart beat. It happens right after diastole, when the heart refills with blood. During systole, the heart's two ventricles contract (squeeze). (The ventricles are the largest parts of the heart, which pump blood to the body and lungs.) During systole, the heart muscle gets an automatic electrical signal that tells the heart to contract (squeeze). This makes the blood flow out of the heart.