Questions and Answers
What is the primary function of the smooth muscle that wraps around arterioles?
To decrease the diameter of the vessel
What is vaso-dilation?
The dilation of blood vessels
What happens to the resistance to blood flow when there is vaso-constriction?
It increases
Who contributed significantly to our understanding of blood flow and resistance?
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What is the main reason why it is harder to blow air through the straw compared to the cardboard tube?
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What is the effect of vaso-dilation on blood flow?
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What is the term for the constriction of blood vessels?
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What is the name of the French gentleman who asked a similar question a long time ago?
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What is the approximate radius of the cardboard tube?
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Why is it easy to blow air through the cardboard tube?
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What is the variable used to represent the length of the cardboard tube?
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What is the main difference between the cardboard tube and the straw?
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What is the approximate radius of the straw?
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What does the experiment demonstrate?
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What is the name of the scientist who put together a set of equations in the 1840s to help answer the question of fluid flow through tubes?
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What is the name of the property of a fluid that determines its resistance to flow?
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What is the relationship between the radius of a tube and the resistance to fluid flow through it?
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What happens to the resistance to fluid flow through a tube if the radius is halved?
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What is the name of the part of the circulatory system that is analogous to a tube in the context of fluid flow?
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What is the formula for resistance to fluid flow through a tube, according to the scientist mentioned in the passage?
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What is the unit of measurement for viscosity?
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What is the result of decreasing the radius of a tube on the resistance to fluid flow through it?
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What is the relationship between the length of a tube and the resistance to fluid flow through it?
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What is the significance of the equation R = 8l / πr^4 in the context of fluid flow through tubes?
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Study Notes
Experiment with Cardboard Tube and Straw
- A person takes a deep breath and blows out through a cardboard tube (like a toilet paper roll) with a length (l) and radius (r) of about 2 centimeters.
- The experiment is repeated with a straw, which has the same length (l) but a smaller radius (r') of about 1 centimeter.
- It is much harder to blow air through the straw than the cardboard tube.
Poiseuille's Equation
- Dr. Jean Louis Marie Poiseuille, a French scientist, developed a set of equations in the 1840s to explain the relationship between fluid flow and tube resistance.
- The equation states that resistance (R) is equal to 8 times the length (l) times the viscosity (eta) divided by pi times the radius (r) to the fourth power.
- R is proportional to 1 over r to the fourth power.
Application to Blood Vessels
- Blood vessels, like tubes, have resistance that affects blood flow.
- Arterioles, part of the circulatory system, have smooth muscle that can relax or constrict, changing their radius.
- When smooth muscle is relaxed (vasodilation), the radius increases, and blood flow is easy with low resistance.
- When smooth muscle constricts (vasoconstriction), the radius decreases, and blood flow is difficult with high resistance.
- Poiseuille's equation helps explain why changes in blood vessel radius affect blood flow.
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Description
An experiment where you blow through a toilet paper roll to understand the relationship between length and radius of a tube. A fun way to learn about physics concepts!
