2. What determines the height of the diastolic pressure?
This is, mainly, determined by the flow of blood into all the organs. As you saw previously, this is determined by the arterioles in the body. All these arterioles resist to various degrees the flow of blood. Together, this is called the peripheral resistance (What is Peripheral Resistance? See section F).
In the diagram, if the resistance is very high (c), the pressure decrease will be very slow during diastole and the diastolic pressure will be high. If however, the peripheral resistance is very low (a or b), the decrease in blood pressure will be very high and the diastolic pressure very low.