Which describes active hyperemia?

• A. Flow independent of tissue demand
• B. Reactive hyperemia
• C. Increased blood flow due to tissue activity
• D. Decreased flow during exercise

Answer: (C)

Active hyperemia is the increased blood flow to a tissue that occurs in response to its own metabolic activity. When a tissue becomes more active, its cells produce more CO2, H+, lactate, adenosine, and other vasodilators. These locally released signals cause arterioles to dilate, increasing perfusion so the tissue gets more oxygen and nutrients and can remove waste efficiently. This flow is driven by the tissue’s demand, which is why the description “increased blood flow due to tissue activity” is the correct one.

Reactive hyperemia, by contrast, refers to a surge in flow after a temporary blockage, not during normal activity. The notion of flow being independent of tissue demand conflicts with the very idea of hyperemia, which is demand-driven. And decreased flow during exercise contradicts the usual increase in perfusion seen with active muscles.