NREMT Advanced EMT Practice Test #3

Answer - C - The lumen is controlled by smooth muscle. Smooth muscle is contained within many internal organs. Through contraction, smooth muscle can bring about changes in size or promote movement. Smooth muscle is found in the arterioles and functions to change the size of the lumen and thus regulates blood pressure. When the smooth muscle contracts, the lumen decreases in size and the blood pressure increases. Conversely, when the lumen increases in size, blood pressure decreases.