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26 Cards in this Set
- Front
- Back
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What can be said when there is no driving force on an ion?
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The electrical driving force and the chemical driving force must be equal and opposite
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What does the Nernst Equation give?
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Potential at which the driving forces are equal and opposite
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What are the three passive electrical properties of excitable cells?
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electromotive force, capacitance, resistance
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What is electromotive force?
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any mechanism that is a course of electrical potential
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Why are the internal and external surfaces of the cell membrane good conductors?
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Because of the charges found on the phospholipid head groups and the proteins
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Why is the inner portion of the membrane an extremely good resistor?
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Because charge does not easily pass through the hydrophobic lipid bilayer. This causes charge to be stored.
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What provides resistance to ion movement?
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The narrow pore of the ion channel
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What happens to the resistance as more ion channels are opened?
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It decreases
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What happens as the diameter of the cell increases?
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The internal resistance decreases
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What creates the resting membrane potential?
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It is created by the movements of ions through channels to create a steady state transmembrane potential difference
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What is the charge of a cell?
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Negative with respect to the outside
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What is the resting membrane potential of excitable cells?
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-50 to -90mV
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What ion is the resting membrane potential closest to?
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K+
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If only K+ channels open, what will happen to the resting membrane potential of the cell?
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It will be equal to that of K+
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What if both Na+ and K+ channels open and ions pass equally?
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The membrane potential would be halfway between that of Na+ and K+
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What can be said about the flow of an ion in relation to the cell's membrane potential?
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The current of an ion will push the membrane potential towards its own potential
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Why is the resting membrane potential closest to that of K+?
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K+ is the most permeable ion
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Which ions are important in determining the value of the resting membrane potential?
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Na+, K+, Cl-
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Why is ECl- equal to the resting membrane potential of the cell?
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It distributes passively across the membrane
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What does the Goldman equation give?
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It gives the resting membrane potential of the cell
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How do K+, Na+, and Cl- move across the membrane which is at rest?
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Passive channels that always stay open
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Which ion do the channels have a higher permeability for?
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K+
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A steady flux of Na+ and K+ occurs since the resting membrane potential is not at EK+ or ENa+. What reestablishes the gradients of these ions?
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Na/K pump
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What does the Na+/K+ pump do?
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3Na out and 2K in; net movement of 1+ outward
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What kind of charge does the Na/K pump create inside the cell?
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Negative charge
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Does the Na/K pump hyperpolarize or depolarize the cell?
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Hyperpolorize (increases its negativity)
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