Which factor primarily motivates choosing vasodilation over tachycardia for local flow changes?

Which factor primarily motivates choosing vasodilation over tachycardia for local flow changes?

• A. Tachycardia increases heart stress
• B. Vasodilation increases blood viscosity
• C. Tachycardia decreases cardiac output
• D. Vasodilation reduces perfusion elsewhere

Answer: (A)

Local flow is adjusted mainly by changing the diameter of small vessels. When a tissue needs more blood, its arterioles dilate, lowering resistance locally and directing more flow to that area without forcing the heart to beat faster. Tachycardia, on the other hand, increases heart rate and overall workload, raising myocardial oxygen demand and stressing the heart. To boost local perfusion efficiently and with less systemic strain, vasodilation is preferred. The other statements don’t capture this key idea: dilation doesn’t increase blood viscosity, tachycardia doesn’t typically decrease cardiac output, and vasodilation’s main effect isn’t simply to reduce perfusion elsewhere but to raise flow to the active tissue.

Local flow is adjusted mainly by changing the diameter of small vessels. When a tissue needs more blood, its arterioles dilate, lowering resistance locally and directing more flow to that area without forcing the heart to beat faster. Tachycardia, on the other hand, increases heart rate and overall workload, raising myocardial oxygen demand and stressing the heart. To boost local perfusion efficiently and with less systemic strain, vasodilation is preferred. The other statements don’t capture this key idea: dilation doesn’t increase blood viscosity, tachycardia doesn’t typically decrease cardiac output, and vasodilation’s main effect isn’t simply to reduce perfusion elsewhere but to raise flow to the active tissue.