PC 2: Flow Down Gradient
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Questions and Answers

According to the Nernst potential equation, what factors does it account for?

  • The charge of the particle
  • Diffusional forces and electrical fields
  • The ratio of the particles concentration intracellular:extracellular
  • Distribution of ions close to either side of the membrane (correct)

    • What does the Nernst potential equation not include?

  • Flow of ions (current)
  • Resistance of the membrane to flow
  • Both A and B (correct)
  • None of the above

    • Why is there an unequal distribution of sodium and potassium across the membrane?

  • Because of the ratio of the particles concentration intracellular:extracellular
  • Because of the Nernst potential
  • Because of the charge of the particles
  • All of the above (correct)

    • Why is it helpful to understand Nernst potentials?

    <p>All of the above</p> Signup and view all the answers

    Why is the membrane potential of a neuron close to, but not the same, as the equilibrium (Nernst) potential for potassium?

    <p>Because of the Goldman Field equation</p> Signup and view all the answers

    In Case 1, which clinical features are less likely to be due to vascular changes in Mary's feet?

    <p>15 seconds capillary refill time on the right great toe</p> Signup and view all the answers

    In Case 2, what aspect(s) of Robert's medical history best explain his foot swelling?

    <p>NYHA stage II heart failure</p> Signup and view all the answers

    According to the text, what problems do most patients with heart failure develop?

    <p>All of the above</p> Signup and view all the answers

    According to the text, which equation describes the movement of charged particles across a membrane based on electrostatic forces?

    <p>Nernst potential</p> Signup and view all the answers

    In which situations does diffusion and hydrostatic pressure act together to facilitate filtration through a capillary?

    <p>Filtration through a capillary</p> Signup and view all the answers

    Which equation describes the balance of a particle moving into or out of a cell, assuming it can cross the membrane?

    <p>Nernst equation</p> Signup and view all the answers

    What is the purpose of a capillary in physiology?

    <p>To transport substances to and from tissues</p> Signup and view all the answers

    Which forces are difficult to measure experimentally?

    <p>Starling forces</p> Signup and view all the answers

    Which equation describes the movement of dissolved particles across a membrane based on their concentration gradient?

    <p>Fick’s law</p> Signup and view all the answers

    What does the Nernst equation tell us about the movement of charged particles across a membrane?

    <p>The direction of particle movement</p> Signup and view all the answers

    Which equation describes the flow of a substance through a capillary?

    <p>Poiseuille’s law</p> Signup and view all the answers

    Which forces can "pull" or "push" the same substance in opposite directions in physiology?

    <p>Starling forces</p> Signup and view all the answers

    What does the term 'flux' describe in physiology?

    <p>Flow along a defined membrane surface area</p> Signup and view all the answers

    Which equation describes the movement of fluid through a system from point A to point B?

    <p>Poiseuille's law</p> Signup and view all the answers

    What is the driving force for the flow of a substance from point A to point B?

    <p>Energy gradient</p> Signup and view all the answers

    What is the relationship between the size of the energy gradient and the amount of flow?

    <p>Directly related</p> Signup and view all the answers

    Which equation describes the movement of charged particles across a membrane based on electrostatic forces?

    <p>Nernst potential equation</p> Signup and view all the answers

    What is the purpose of a capillary in physiology?

    <p>To facilitate fluid flow</p> Signup and view all the answers

    Which physico-chemical law is most relevant for understanding the movement of charged particles across a membrane?

    <p>Ohm's law</p> Signup and view all the answers

    According to Fick's law, what factors affect the rate of diffusion across a membrane?

    <p>Concentration gradient and surface area</p> Signup and view all the answers

    What does Ohm's law state about the relationship between current, voltage, and resistance?

    <p>Current is directly proportional to resistance and directly proportional to voltage</p> Signup and view all the answers

    What does the Nernst potential equation describe?

    <p>The movement of charged particles across a membrane based on their concentration gradient</p> Signup and view all the answers

    What is the purpose of a capillary in physiology?

    <p>To facilitate the exchange of oxygen and carbon dioxide between the blood and tissues</p> Signup and view all the answers

    Which of the following best explains Robert's foot swelling in Case 2?

    <p>Decreased cardiac output</p> Signup and view all the answers

    What is the most likely cause of Robert's shortness of breath in Case 2?

    <p>Increased respiratory rate</p> Signup and view all the answers

    Which of the following is a consequence of impaired 'forward-flow' in heart failure?

    <p>Impaired function of the kidneys</p> Signup and view all the answers

    What happens to blood in heart failure due to 'fluid backup'?

    <p>It backs up in the venous system</p> Signup and view all the answers

    According to Fick's law, the rate of diffusion is affected by various parameters. Which of the following is NOT one of those parameters?

    <p>Electrostatic pressure gradient</p> Signup and view all the answers

    According to Poiseuille's law, which of the following is the most important determinant of resistance in a vessel?

    <p>Cross-sectional size of the vessel (radius)</p> Signup and view all the answers

    Which of the following is NOT a process in the body that depends on the flow of a substance down a gradient?

    <p>Na+/K+ pump</p> Signup and view all the answers

    According to Pouiseille's law, what happens to the flow when the radius of a tube/vessel decreases by half?

    <p>The flow decreases by a factor of 4</p> Signup and view all the answers

    Which of the following is a factor that can affect the flow/flux of substances through capillaries?

    <p>Solubility of the substance</p> Signup and view all the answers

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