Final answer:
Blood flow in small arteries and arterioles is regulated by vasoconstriction, which increases resistance and reduces flow, and vasodilation, which decreases resistance and increases flow.
Step-by-step explanation:
In small arteries and arterioles, blood flow to organs is controlled by altering resistance. Vasoconstriction is the process of narrowing the blood vessel, which increases resistance and blood pressure, but reduces blood flow. Conversely, vasodilation is the widening of the blood vessel, which decreases resistance and increases blood flow to the tissues. Thus, the correct statement is that vasodilation decreases resistance and increases flow. Vasoconstriction and vasodilation are essential mechanisms for regulating blood pressure and ensuring adequate blood flow to various parts of the body depending on physiological needs.