According to the Poiseuille equation, if the radius of an arteriole is reduced to half its original value while all other determinants remain constant, blood flow through that vessel will:

• A Fall to one half of the original flow
• B Fall to one quarter of the original flow
• C Fall to one sixteenth of the original flow ✓
• D Rise fourfold because velocity increases

Explanation

Poiseuille's law states that flow is proportional to the fourth power of radius (Q proportional to r^4 times delta P divided by 8 eta L). Halving the radius gives (1/2)^4, which equals 1/16 of the original flow. This extreme radius dependence is why minute changes in arteriolar diameter produce powerful changes in organ blood flow and vascular resistance, and it kills option B, which wrongly applies a square relationship.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

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