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20 Cards in this Set
- Front
- Back
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Extracellular and Intracellular concentration of Potassium |
5 & 150 |
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Extracellular and Intracellular concentration of Sodium
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150 & 5 |
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Concentration Gradient
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the difference in concentration of a molecule between twolocations (e.g., inside and outside the cell).
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Determinants of Diffusion of Ions
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Chemical Driving Force Electrical Driving Force |
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Chemical Driving Force
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The concentration gradient across the membrane
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Electrical Driving Force |
Separation of charges causes an electrical gradienta cross the membrane. Negative areas tend to attract positive ions, etc. |
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Electrochemical Gradient |
The driving force for ions is normally a combination of both chemical and electrical driving forces |
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Membrane Potential |
the potential (voltage) difference across the cell membrane, i.e., the voltage difference between the inside of the cell and the outside of the cell |
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Measurement of Membrane Potential
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normally measured with electrodes
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The Resting Membrane Potential |
when the cell is not firing action potentials. Inside negative compared to outside. Most neurons measure around -70 mV |
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Equilibrium Potential |
voltage at which the flux of a particular ion due to the concentration gradient for the ion balances the opposing flux due to the electrical gradient for that ion. |
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Nernst Equation
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used for calculating the equilibrium potential for an ion.
E(ion) = 60/z( log( [X]o/ [X]i)) |
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Resting Membrane Potential Equation |
Em =( gK(EK) + gNa(ENa)) /gK + gNa
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Net Flux |
Permeability x Driving Force |
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primary determinants of the restingmembrane potential
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Differences in the concentrations
Differences in the membrane permeability |
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Driving Force
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(EX – Em) Equilibrium potential minus membrane potential
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Stable Membrane Potential |
gK(Em-EK) = - gNa (Em-ENa)
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Na,K ATPase
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A transporter in the cell membrane which pumps 3 Na+ out per 2 K+in. Note thatthis means that this pump is electrogenic
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Ion Channels
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proteins in the membrane that form water-filled pores. They conduct ionswhen open and do not conduct ions when closed
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Characteristics of Ion Channels
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are selective.
Many different types exist, can be in different configurations |
