Question

with a decrease in resistance in blood vessels, blood flow increases. which of the following causes decreased resistance?

• low blood viscosity decreases resistance in blood flow.
• high blood viscosity decreases resistance in blood flow.
• low ph in the blood will decrease resistance in blood flow.
• changes in red blood cell shape will decrease resistance in blood flow.

Explanation:

🆕 New Concept Discovered: Hemodynamics and Blood Flow Resistance
How physical factors affect blood movement.

Step 1: Understand resistance and viscosity

Resistance is the friction or opposition that blood encounters as it flows through blood vessels.

Viscosity refers to the "thickness" or internal friction of a fluid. Think of water (low viscosity) versus honey (high viscosity). A thinner fluid flows much more easily through a tube than a thick, sticky fluid.

Step 2: Relate viscosity to resistance

According to Poiseuille's Law, resistance (\(R\)) in a vessel is directly proportional to the viscosity (\(\eta\)) of the fluid:

$$ R \propto \eta $$

This means:

• Lower viscosity (thinner blood) leads to decreased resistance, allowing blood to flow more easily.
• Higher viscosity (thicker blood) leads to increased resistance, making it harder for blood to flow.

Step 3: Evaluate the options

• Low blood viscosity decreases resistance in blood flow: This is correct because thinner blood experiences less internal friction, reducing overall resistance.
• High blood viscosity decreases resistance in blood flow: This is incorrect because thicker blood increases friction and resistance.
• Low pH in the blood will decrease resistance in blood flow: pH primarily affects chemical processes and oxygen binding, not the direct physical resistance of blood flow.
• Changes in red blood cell shape will decrease resistance in blood flow: Abnormal shapes (like in sickle cell anemia) typically increase resistance by causing cells to clump or clog vessels.

Answer:

Low blood viscosity decreases resistance in blood flow.