Term
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Definition
| arises from the interactions of ion channels and ion pumps embeded in the membrane, which produce different concentrations of electrically charged ions on the intracellular and extracellular sides of the membrane |
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Term
| Membrane Potential Functions: |
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Definition
| allows a cell to function as a battery, providing power to operate a variety of "molecular devices" embedded in the membrane; in electrically excitable cells (neurons/muscle cells) it is used for transmitting signals between different parts of a cell |
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Definition
| by opening or closing of ion channels at one point in the membranem, producing a local change in the membrane potential that causes electric current to flow rapidly to other points in the membrane |
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Term
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Definition
| when the membrane potential of a cell can go for a long period of time without changing significantly; nonexcitable cells; excitable cells in the absence of excitation |
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Term
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Definition
| in membrane potential that follow a fixed time course; large |
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Term
| In excitable cells, the three possible states: |
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Definition
| graded membrane potential(of variable amplitide) and action potential(large, all-or-nothing on fixed time course) |
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Term
| Examples of excitable cells |
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Definition
| Neurons, muscle cells and secretory cells in glands |
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Term
| Amplitude of an action potential |
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Definition
| independent of the amount of current that produced it |
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Term
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Definition
| do NOT create larger action potntials |
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Term
| Action Potentials are said to be |
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Definition
| all-or-nothing, since they either occur fully or they do not occur at all |
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Term
| The frequency of action potentials |
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Definition
| encodes for the intensity of a stimulus |
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Term
| Electrical potential is applied across the membrane |
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Definition
| electrical charges of the ion causes them to move through the membrane, even though no concentration difference exists to cause movement |
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Term
| Concentration of negative ions is the same on both sides. What happens if a positive charge has been applied to the right side of the membrane and a negative charge to the left |
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Definition
| an electrical gradient across the membrane is created |
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Term
| Positive charge _____ the negative ions, whereas the negative charge ______ them |
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Definition
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Term
| when the concentration differences rises enough, what happens? |
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Definition
| the two effects(concentration and ion charges) balance eachother out |
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Term
| The Nernst Equation determines |
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Definition
| the electrical difference that will balance a given concentration difference of univalent ions (such as sodium ions) at normal body temperature( 37 degrees C) |
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Term
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Definition
| EMF(mvolts)= +/- 61 log (C1/C2) |
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Term
| EMF(mvolts)= +/- 61 log (C1/C2) |
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Definition
EMF: Electromotive Force (voltage) between side 1 & 2 of the membrane
C1: concentration on side 1
C2: concentration on side 2
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Term
| Diffusion potentials alone caused by potassium and sodium diffusion |
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Definition
Gives a membrane potential of about -86 millivolts (almost all of this being determined by potasium diffusion;
An additional -4 millivolts contributed to the membrane potential by the continuously acting electrogenic Na+/K+ pump, giving a net membrane potential of -90 millivolts |
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Term
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Definition
| nerve signals are transmitted, which are rapid changes in the membrane potential that spreads rapidly along the nerve fiber membrane |
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Term
| What starts an Action Potential |
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Definition
| sudden change from the normal resting negative membrane potential to a positive potential; ends with an almost equally rapid change back to the negative potential |
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Term
| To conduct a nerve signal |
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Definition
| the Action Potential moves along the nerve fiber until comes to the fiber's end |
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Term
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Definition
membrane potential post action potential;
"polarized" bc -90millivolts negative membrane potential is present |
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Term
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Definition
the membrane suddenly becomes permeable to sodium ions, allowing trememdous numbers of positively charged sodium ions to diffuse to the interior axon;
Normally pollarized state(90millivolts) is immediately neutrallized by inflow of positively charges sodium ions (positive potential rising)=Depolarized |
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Term
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Definition
a few 10,000ths of a second after the membrane becomes highly permeable to sodium ions, the sodium channels begin to close and potassium channels open more than normal;
Rapid diffusion of potassium ions to the exterior reestablished the normal negative resting membrane potential |
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