BIOL 2420 Lecture Notes - Lecture 3: Heart Valve, Blood Pressure, Atrioventricular Node
15 Nov 2016
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Document Summary
Atria and ventricles both have their own systole and diastole: but usually we talk about the ventricles. Systole - ventricular contraction: contraction and emptying of the heart. Pressure in the atria is more than the pressure in the ventricle. Increasing ventricular pressure forces the semilunar valves open: the arteries pressure is lower than the ventricles. About half of the blood in the ventricle enters the aorta/pulmonary arteries: referred to as the stroke volume, the amount of blood that is ejected from the ventricles. Semilunar valves close when ventricular pressure falls below aortic/pulmonary artery pressure: when the blood trickles in reverse, the bathe the semilunar valves, and closes them, second heart sound. Diastole - ventricular relaxation: relaxation and filling of the heart. Ventricular pressure is too high for the av valves to open: blood cannot enter the ventricle, passive ventricular filling. Ventricle pressure is lower than the atria above. Blood entering the relaxed atria beings to passively flow into the ventricles.
