Final answer:
The radii of the arterioles constrict by a factor of 16 times when they decrease to one-half of their original radius.
Step-by-step explanation:
The arterioles leading to an organ constrict in order to decrease flow to the organ. The radii of the arterioles constrict by a factor of 16 times when they decrease to one-half of their original radius. This means that the resistance to flow will increase 16 times when the radii of the arterioles constrict.