ABSTRACT
Because the blood vessels are elastic and have smooth muscle in their walls, contraction or relaxation of the smooth muscle can quickly redistribute blood between the periphery and the heart to inuence cardiac lling and thus cardiac output. Even though the right ventricle is not essential for life, its functioning acts to reduce the central venous pressure to facilitate venous return [1]. It largely determines the magnitude of the cardiac output by inuencing the degree of lling of the le heart. Dynamic changes in venous tone, by redistributing blood volume, can thus, at rest, change cardiac output over a range of more than ±20%. e dimensions of the vasculature inuence both blood ow-by way of their resistive properties-and contained blood volume-by way of their capacitive properties. e arteries have about 10 times the resistance of the veins, and the veins are more than 10 times as compliant as the arteries.
