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.
Overview. The human heart has 4 valves. The mitral valve connects the left atrium (LA) and the left ventricle (LV). The mitral valve opens during diastole to allow the blood flow from the LA to the LV. During ventricular systole, the mitral valve closes and prevents backflow to the LA.he human heart has 4 valves. The mitral valve connects the left atrium (LA) and the left ventricle (LV). The mitral valve opens during diastole to allow the blood flow from the LA to the LV.