30 Questions
Which law describes fluid flow down a gradient?
Poiseuille's law
What is the driving force for the flow of a substance?
Energy gradient
What is directly related to the amount of flow between two points in a system?
Size of the energy gradient
What is the greater the gradient, the greater the flow?
True
What is the term for factors that resist the flow down gradients?
Resistance
What is the term for the movement of a substance from one point in a system to another point in the system?
Flow
Which of the following clinical features is less likely to be due to vascular changes in Mary's case?
15 seconds capillary refill time on the right great toe
How many physico-chemical laws are in play in Mary's case?
One
Which of the following is the best explanation for Robert's foot swelling?
NYHA stage II heart failure
Which of the following is the best explanation for Robert's shortness of breath?
Long history of heart failure
How many general types of problems do most patients with heart failure develop?
Three
Which of the following is true about blood flow in the venous system in heart failure?
Blood flow is decreased
Which parameter in Poiseuille's law determines the rate of flow through a tube?
Radius of the tube
Which of the following substances is more likely to have a higher viscosity?
Syrup
What happens to the flow when the hydrostatic pressure difference between two points in a tube increases?
Flow increases
What happens to the flow when the radius of a tube decreases by half?
Flow decreases
Which of the following parameters does NOT impact the flow through a tube?
Length of the tube
Which of the following is NOT a process in the body that depends on the flow of a substance down a gradient?
Fluid moving from a high concentration to a low concentration
According to Fick's law, what factors determine the rate of diffusion across a membrane?
The solubility of the substance in the membrane
What is the relationship between the number of transporters and the surface area to volume ratio in cells specialized for transporting solute?
They are directly proportional
What is the main factor that determines the movement of charged particles across a membrane?
The charge of the particle
What is the relationship between the number of channels for a charged particle and the resistance in Ohm's law?
They are inversely proportional
What happens to the current when the voltage increases in Ohm's law?
The current increases
According to the text, when is Ohm's law most useful in biology?
When thinking about unequal distributions of charges very close on either side of a membrane
According to Poiseuille's law, which of the following is the most important determinant of resistance in a tube?
Tube radius
Which of the following is a caveat of Poiseuille's law?
It is accurate for flexible tubes
According to Fick's law, which of the following affects the rate of diffusion?
Surface area
Which equation represents Fick's law?
$F = k \cdot A(C_A - C_B)t$
What is the driving force for diffusion according to Fick's law?
Concentration gradient
What is the effect of increasing the thickness of the membrane on diffusion according to Fick's law?
Decreases flow
Study Notes
Fluid Flow and Gradients
- Fick's law of diffusion describes fluid flow down a gradient, where the driving force is the concentration gradient.
- The flow of a substance is directly related to the concentration gradient between two points in a system.
Resistance to Flow
- The term for factors that resist the flow down gradients is resistance.
- In the context of Poiseuille's law, resistance is affected by the length and radius of the tube, as well as the viscosity of the fluid.
Poiseuille's Law
- Poiseuille's law states that the flow rate of a fluid is directly proportional to the fourth power of the radius of the tube, and inversely proportional to the viscosity of the fluid and the length of the tube.
- The parameter in Poiseuille's law that determines the rate of flow through a tube is the radius of the tube.
- If the radius of a tube decreases by half, the flow rate decreases by a factor of 16.
Fick's Law of Diffusion
- Fick's law of diffusion states that the rate of diffusion is proportional to the concentration gradient and inversely proportional to the thickness of the membrane.
- The driving force for diffusion according to Fick's law is the concentration gradient.
- Increasing the thickness of the membrane decreases the rate of diffusion according to Fick's law.
Ohm's Law
- Ohm's law is useful in biology when studying the flow of charged particles across a membrane.
- According to Ohm's law, the current is directly proportional to the voltage and inversely proportional to the resistance.
- The number of channels for a charged particle affects the resistance in Ohm's law.
Heart Failure
- In heart failure, the venous system is affected, leading to increased pressure and swelling in the legs.
- Robert's shortness of breath is likely due to pulmonary edema, a complication of heart failure.
Test your knowledge of Poiseuille's law and its limitations with this quiz. Learn about the factors that affect resistance in fluid flow through tubes, including tube shape, fluid flow characteristics, and tube flexibility. Explore how these factors impact the accuracy of Poiseuille's law in different scenarios.
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