If the radius of blood vessels of a person decreases his/her blood pressure will__________?
Correct answer: B. Increase
- A. Decrease
- B. Increase
- C. Remain Same
- D. Becomes zero
Explanation
For a given blood flow, reducing vessel radius greatly increases resistance because resistance varies inversely with the fourth power of radius, R ∝ 1/r^4. The heart must therefore generate greater pressure, so blood pressure tends to increase; students may choose decrease by assuming a narrower vessel carries less pressure rather than offering more resistance.
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About Blood Vessels
Blood vessels include arteries, arterioles, capillaries, venules and veins, whose wall thickness, elasticity, lumen size and valves suit their roles in circulation. Questions compare pressure and blood flow in each vessel and distinguish pulmonary vessels, which carry blood to and from the lungs, from systemic vessels.
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