See figure 14-37 for the change in pressure with the cardiac cycle. Systolic pressure is 125 vs Diastole of 75. Thus pressure is maintained even during diastole when the ventricle are not contracting. When the vessel expands due to the push of blood from ejection during systole, it recoils during diastole, thereby continuing to drive blood through the system. The push of blood from the ventricles causes expansion of the vessel walls.
Arterial compliance decreases with age.
The arterioles are a major determinant of MAP via their role in affecting total peripheral resistance. Now let consider the flow to a vascular bed. Be forewarned that the relations that we previously described play a slightly different role here. What we are talking about now has to do with flow to an organ or a particular vascular bed rather than total flow and pressure in the whole system. If Resistance increases, Flow to the organ will decrease.