Whats the difference between the systolic and the diastolic pressure?

Arteries and veins. Systolic pressure is the pressure in your artery during during cardiac contraction as blood rapidly flows into the arteries. It measures to certain degree the elasticity of the vessel. Diastolic pressure is the pressure after contraction when no active flow is going and measures the resting tone of the artery. CVP is the venous pressure closest to the heart or the vena cavae.