The human circulatory system can be thought of as a closed system of interconnecting pipes through which fluid is continuously circulated by two pumps. The two pumps, the right and left ventricles of the heart, work as simple two-stroke force pumps. The muscles of the heart regulate the force by contracting and relaxing. The contraction (systole) lasts about 0.2 s, and a complete systole/diastole (contraction/relaxation) cycle lasts about 0.8 s.
For blood pressure and speeds in the normal range, the volume flow rate of blood through a blood vessel is directly proportional to the pressure difference over a length of the vessel and to the fourth power of the radius of the vessel.
The total mechanical energy per unit volume of blood just as it leaves the heart is:  ${\rho }_{blood}=1050kg/m^3$
$E/V=\rho gh+P+\frac{1}{2}\rho v^2$
Why is diastolic blood pressure much lower than systolic pressure? (Note: A typical systole/ diastole reading in mm Hg is 120/80)