membrane potential

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Question

Answer

Electrical disturbance propagated to the plasma membrane of excitable cells

Action Potential (AP)

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An electrical state across the plasma membrane of all cells, characterized by a (-) charge inside relative to the outside. This is necessary for the cell to fire an AP.

Resting Membrane Potential (RMP)

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RMP=

-90 mv

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Na+ (outside)

142 mEq/L

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Na+ (inside)

14 mEq/L

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K+ (outside)

4 mEq/L

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K+ (inside)

140 mEq/L

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The flow of ions across the plasma membrane down their electrochemical gradients is directly responsible for generating much of the RMP

memorize it

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__________are caused by diffusion ions across the plasma membrane

Membrane potentials

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highly concentrated inside

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diffuses outside creating electronegativity inside while electropositivity outside the plasma membrane

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Diffusion stops when _____________ is great enough to block further net diffusion to the exterior despite high K concentration inside

diffusion potential

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In mammalian nerve fiber K diffusion potential is

(-) 94 mV

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highly concentrated outside; low concentration inside

Na ions

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diffusion to the inside creates a membrane potential which is (+) inside and stops when diffusion potential = (+) 61 mV is reached

Na ions

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Relation of diffusion to the concentration difference

Nernst Potential

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Recall the Nernst equation

+/- 61 x log conc. inside divided by conc. outside

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the diffusion potential level across a membrane that exactly opposes net diffusion of a particular ion through the membrane

Nernst Potential

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___________ are most important ions involved in the development of membrane potentials in nerve, muscle as well as neuronal cells in the nervous system

Na, K and Cl

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The degree of importance of each of the ions in determining the voltage is proportional to the _________ for that particular ion

membrane permeability

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A (+) ion concentration gradient from the inside to the outside of the membrane causes __________ inside the membrane

electronegativity

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__________ inside are left behind creating electronegativity inside plus Cl ions outside diffuse to the inside following Na ions

Nondiffusible (-) anions

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Permemability of Na and K channels undergo rapid changes during

transmission of nerve impulse

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________does not change charges greatly

Cl permeability

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Rapid changes in Na and K permeability are primarily responsible for _______________

signal transmission in neurons

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continually transports Na to the outside and K ions to the inside of the cell

Na - K Pump

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an electrogenic pump because more (+) charges are pumped to the outside than to the inside: 3Na + outside; 2K = outside

Na - K Pump

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leaves a net deficit of (+) ions inside

Effects Na- K Pump

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causes (-) potential inside the cell

Effects Na- K Pump

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causes a large concentration gradient for na and K across the resting nerve membrane

Effects Na- K Pump

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indirectly contributes to the establishment of RMP

Effects Na- K Pump

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The _______________ is used to calculate the diffusion potential when the membrane is permeable to several different ions

Goldman Equation

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When a membrane is permeable to several different ions, the diffusion potential that develops depends on three factors:

1) the polarity of the electrical charge of each ion 2) the permeability of the membrane (P) to each ion 3) the concentrations (C) of the respective ions on the inside (i) and outside (o) of the membrane

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Gives the calculated membrane potential on the inside of the membrane when two univalent positive ions, K+ and Na+, and one univalent negative ion, Cl- are involved.

Goldman Equation/Goldman-Hodgkin-Katz

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Several key points become evident from the Goldman equation: _________,___________, and ____ are the most important ions involved in the development of mebrane potentials in nerve and muscle fibers, as well as in the neuronal cells in the nervous system.

sodium, potassium, and chloride

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The concentration of _______,__________,________ across the membrane helps determine the voltage of the membrane potential

sodium, potassium, and chloride

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the quantitive importance of _______,_____,_______ in determining the voltage is proportional to the ________________ for that particular ion.

membrane permeability

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If the membrane has _______ permeability of potassium and chloride ions, the membrane potential becomes entirely dominated by the concentration gradient of sodium ions alone, and the resulting potential will be equal to the _________for sodium

zero; Nernst potential

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Contribution of the Na+ K+ Pump

Origin of the Normal Resting Potential:

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- Contribution of the Potassium Diffusion Potential

Origin of the Normal Resting Potential:

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Contribution of the Sodium Diffusion through the Nerve Membrane

Origin of the Normal Resting Potential:

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