Final answer:
Conditions that decrease peripheral vascular resistance, such as vasodilation and venoconstriction, can lead to an increase in preload, which affects cardiac output as governed by the Frank-Starling principle.
Step-by-step explanation:
The question addresses how certain conditions can decrease peripheral vascular resistance and thus increase preload in the cardiovascular system. Decreased peripheral resistance is usually achieved through the process of vasodilation, which allows blood vessels to widen and blood to flow more freely. This process decreases resistance and increases blood return to the heart, leading to a rise in preload. Preload refers to the end-diastolic volume that stretches the right or left ventricle of the heart to its greatest geometric dimensions under variable physiologic demand.
Conditions that reduce compliance, such as arteriosclerosis, can increase peripheral resistance, leading to hypertension and making the heart work harder. On the other hand, factors like vasodilation, decreased blood vessel length and diameter, lower blood viscosity, and venoconstriction in the venous system can decrease peripheral resistance. Specifically, venoconstriction enhances venous return and thus increases preload.
In addition to structural changes in the blood vessels, the volume of blood in the body and its viscosity can influence both resistance and preload. The Frank-Starling principle states that the greater the volume of blood entering the heart during diastole (preload), the stronger the subsequent contraction will be, assuming normal cardiac function. Overall, a decrease in peripheral resistance allows for an increase in preload, which then influences cardiac output according to the heart's intrinsic regulatory mechanisms.