Which of the following statements concerning regulation of blood flow is TRUE?
A. In the systemic circuit, high levels of CO2 and metabolites tend to cause contraction in the smooth muscle of arteriole walls.
B. In the systemic circuit, increased levels of metabolic waste products and decreased oxygen concentration in tissues promote hyperemia through the tissues.
C. The resistance to blood flow in brain and heart vascular beds does not vary in response to changes in local gas or metabolite concentrations.
D. According to flow autoregulation, if blood pressure to an arteriole is decreased, blood flow will not return toward its original level until the original blood pressure is restored.
E. If blood flow to a tissue is blocked for a period of time and then the block is removed, the result is a reactive hyperemia in which blood flow through the affected tissue remains low.
Answer: B
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