Which condition would promote vasodilation in systemic capillary beds?

Which condition would promote vasodilation in systemic capillary beds?

• A. Local increase in pH
• B. Local increase in CO2
• C. High systemic oxygen
• D. High sympathetic tone

Answer: (B)

Metabolic regulation of blood flow in tissues is driven by local chemical signals that tell capillaries to adjust flow to match activity. A rise in local carbon dioxide indicates increased cellular respiration and, as CO2 increases, the resulting slight acidification (lower pH) of the surrounding smooth muscle causes the arteriolar smooth muscle to relax. This dilation raises blood flow to the area, helping to wash out CO2 and bring in oxygen. So a local increase in CO2 promotes vasodilation. In contrast, a local rise in pH implies less metabolic waste and tends to constrict, high oxygen availability reduces the need for extra flow, and high sympathetic tone generally causes vasoconstriction, not dilation.

Metabolic regulation of blood flow in tissues is driven by local chemical signals that tell capillaries to adjust flow to match activity. A rise in local carbon dioxide indicates increased cellular respiration and, as CO2 increases, the resulting slight acidification (lower pH) of the surrounding smooth muscle causes the arteriolar smooth muscle to relax. This dilation raises blood flow to the area, helping to wash out CO2 and bring in oxygen. So a local increase in CO2 promotes vasodilation. In contrast, a local rise in pH implies less metabolic waste and tends to constrict, high oxygen availability reduces the need for extra flow, and high sympathetic tone generally causes vasoconstriction, not dilation.