Final answer:
Arteriolar radius can change through vasoconstriction and vasodilation, which have a significant impact on blood flow.
Step-by-step explanation:
The radius of the arterioles can change through a process known as vasoconstriction and vasodilation. Vasoconstriction involves the contraction of smooth muscles in the arteriole walls, resulting in a decrease in radius. On the other hand, vasodilation involves the relaxation of smooth muscles, leading to an increase in radius.
The impact of arteriolar radius changes on blood flow is significant. The resistance to blood flow is inversely proportional to the radius raised to the fourth power, according to Poiseuille's law. Therefore, even small changes in radius can have a large effect on blood flow. A decrease in arteriolar radius, such as from plaques in the arteries, can greatly reduce blood flow, while an increase in arteriolar radius can increase blood flow.