Final answer:
Blood flow to the skin is primarily controlled by the sympathetic system, which exerts control through vasoconstriction regulated by neural inputs such as norepinephrine, that helps in the regulation of body temperature.
Step-by-step explanation:
Blood flow to which organ is controlled primarily by the sympathetic system rather than by local metabolites? The answer is a. Skin.
The sympathetic system is primarily responsible for controlling blood flow to certain organs in the body. For instance, during fight-or-flight responses, the sympathetic system causes vasoconstriction in the vessels leading to the kidneys and most of the digestive and reproductive organs, whereas it causes vasodilation in vessels of the heart, lungs, liver, and integument which includes the skin. The skin particularly stands out because the regulation of its blood flow is predominantly governed by sympathetic tone, due to the lack of substantial parasympathetic input to the systemic circulatory system. As a result, the skin's blood vessels respond primarily to neural inputs, such as the release of norepinephrine, which causes constriction and helps regulate body temperature.