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.
The normal cardiac cycle, showing pressure relationships between the left-sided heart chambers. During diastole, the mitral valve (MV) is open, so that the left atrial (LA) and left ventricular (LV) pressures are equal. In late diastole, LA contraction causes a small rise in pressure in both the LA and LV (the a wave).