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19 Cards in this Set
- Front
- Back
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State whether the intracellular or the extracellular concentration is higher for the following ions: K+, Na+, Cl-, and Ca++. Will the chemical driving force of their concentration gradients tend to push these ions into the cell or out of the cell?
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K+ and Ca++ would be pushed out;Cl- and Na+ would rush in the cell
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If a student is told the concentration of ions on each side of a membrane, the electrical potential difference across the membrane, and the equilibrium potential for each ion, the student should be able to answer the following questions:
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Inside Cell: K+ Ca++ (higher) Cl- Na+ (lower)
Outside Cell: Cl- Na+ (higher) K+ Ca++ (lower) |
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What is the direction and strength of the chemical driving force? If an ion was responding to just the chemical force how would it move?
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Chemical force pertains to the concentration of ions, will travel from high concentration to low without any electrical driving force present…
1. K+ would rush out of the cell 2. Na+ would rush into the cell 3. Ca++ will rush out; Cl- will rush in |
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If the ion was responding only to the electrical driving force of the membrane potential, which way would it move?
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Any region must have an equal number of + and – ions (essentially they “pair up” and cancel each other out)
-so a negative ion would travel to the more positive space to find its “match”. -K+ Ca++ and Na++ would want to be inside the cell, Cl- would want to be outside |
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Which force is stronger, the electrical driving force or the chemical driving force? What is the net effect of these forces; i.e., what is the electrochemical gradient (electrochemical driving force)?
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Nernst potential (61.5 is for ions with +1 charge; use –61.5 for ions with –1 charge)=
E(ion) =61.5 log([outside]/[inside]) |
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Be able to state how EK+ or ENa+ changes if the extracellular concentration of K+ or Na+ is raised or lowered.
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1. EK+ decreases if K+ moves out of the cell and increases if K+ moves in
3. ENa+ decreases if Na moves in and increases if Na+ moves out |
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Be able to state how the membrane potential changes if the extracellular concentration of K+ or Na+ is raised or lowered.
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If the extracellular concentration of K+ is raised, the RMP is increased (more positive)
If the extracellular concentration of K decreases, the RMP decreases (more negative) If the extracellular concentration of Na increases, the RMP increases (more positive) If the extracellular concentration of Na decreases, the RMP decreases (more negative) |
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Be able to state how the membrane potential changes if the membrane permeability to (and the conductance of) Na+, K+ or Cl- changes.
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(Actual membrane potential of cell is balance between EK+ (which changes if K+ concentration changes) and ENa+.
At rest the cell is much more permeable to K+ than to Na+ so the membrane potential is closer to EK+.) Nernst Equation: Quantifies equilibrium potential, Single ion, Permeability is not a factor Goldman Equation: Multiple ions, Permeability is a factor |
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Be able to state how the membrane potential changes if EK+ or ENa+ changes.
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If EK becomes more negative, membrane potential becomes more negative; if ENa+ becomes more positive the membrane potential becomes more positive
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Be able to explain the role of the Na+ - K+ pump in maintaining the cell membrane potential.
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Both ions are pumped against their concentration gradient
(3 Na ions go out for every 2 K ions that are pumped in, each cycle the cell becomes more negative) keeping K+ concentration higher inside and Na+ higher outside while maintaining cell volume as well. *Oubain inhibits this pump |
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hyperkalemia
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Higher extracellular Potassium (-> abnormal function of muscle, heart and nerve)
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hypokalemia
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Lower extracellular Potassium
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hypernatremia
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High Sodium outside (usually due to dehydration)
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hyponatremia
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Low Sodium outside (usually due to over hydration)
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hypercalcemia
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High Calcium outside
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hypocalcemia
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Low Calcium outside
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Membrane polarization
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the membrane is charged and is more negative on the inside, more positive outside
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Depolarization
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A reduction in the membrane potential since the absolute difference in potential between the inside and outside of the cell has decreased
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Hyperpolarization
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membrane becomes more negative inside
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