| Author | 5 Posts |
kkr
Forum Junior
Topics: 12
Posts: 25
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hello ssrpk,
can you please explain me the difference between equilibrium potential and membrane potential.
know that intracellular pottasium is high and extracellular sodium is high.restimg membrane potential is -90 and to get into equilibrium position the ions tend to be in equloibrium with intracellular environment,If i get the concept right.
I am not able to figure out how sodium has - 45 and pottasium +15??
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| kkr
Forum Junior
Topics: 12
Posts: 25
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also the explanation for cardiac muscle excitation for raised extracellular pottasium.If extracellular pottasium more the cell is hyperpolarised,how can the change in ions to a minimal level will alter the excitability.confused about this.can u please help me out.
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| SDK
Forum Fanatic
Topics: 537
Posts: 1,587
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According to Nerst equation.....
Equilibrium potential is that potential which block furthur flux of ions across CM...........
Now RMP is -90...
Eq-Na+ is +45.
Eq-K is -105
Eq-Cl is -90
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| kkr
Forum Junior
Topics: 12
Posts: 25
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thank you very much SDK
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| ssrpk
Forum Fanatic
Topics: 154
Posts: 2,819
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well realize one thing!
as long as these conc. of K+ and Na+ are maintained in and out of the celll ,there will be no iso-electric point for the cell tht means potential difference wil be shifting back and forth for each ion during diff. phases [resting and action potentail]
therefore any change in conc. diff. will hv an impact on it eq.potential and inturn will affect resting membrane potential!
because K+ flux is greater among other ions during restinmg phase therefore a change in it's ECF conc. will hv dramatic affect on it's eq.potential a/a RMP!
High K+ in ECF - lower gradient for outflux during repolariztion -depolarization!
low K+ in ECF- huigh gradient for outflux--- hyperpolarization!
Cardiac Pacemaker Cells:
Hyperkalemia: repolarization is slowed down[conc. effect] [refractory period inc.]and phase IV is prolonged due to hiugh permeability of K+(more efflux) which reduces the tendency of cell to get depolarized.
Hypokalemia: repolarization speeds up [conc. effect] [refractory period dec.] and Phase IV gets shortened due to low permeability of K+ [lesser efflux] which enhances the tendency of the cell to get depolarized.
N.B. remember tht this permeability effect will not hv significant effect on non-pacemaker cells!
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