action potential

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student12
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action potential

Post by student12 » Thu May 25, 2006 9:42 am

my query is on the resting cell. Why is it -70mV when both K+ and Na+ are positively charged. So why does resting cell is negatively charged.

Doc44
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Post by Doc44 » Thu May 25, 2006 2:00 pm

At a point of increased permeability on the neurolemma Na+ goes into the nerve cell at a greater rate than K+ goes out of the nerve cell (neron). This causes an results in a proportinate increase in the Ca- ions on the out side of the neuron. This relative increase in negativity is the nerve impulse.

Doc44

There are no simple answers to complex questions, but this generalization get the idea across, I hope.

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Post by Ultrashogun » Thu May 25, 2006 5:24 pm

Potential does not dipend on the charges themselves, but on the difference of the concentrations of the charges. So if you have lots of positive charges on the outside of the membrane, and not so many on the inside, then the inside is on the negative side of a potential.

The key word is difference.

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MrMistery
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Post by MrMistery » Thu May 25, 2006 5:39 pm

actually the answer is a completely different one. Ultrashogun had it with the concentrantion of charges. There are a lot of positive Na and negative Cl outside. Inside, there are a lot of positive K and negative organic molecules. It is this immense concentrantion of negatively charged organic molecules on the inside, correlated with the slightly smaller K concentrantion inside than the Na concentration outside that gives the plasma membrane a resting potential with more negative charges on the inside.
However, you should know that only very few of the total ions contribute to this equilibrium, those near the membrane. The rest of the citosol and extracellular fluid are pretty much neutral from an electrical point of view.
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2810712
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Post by 2810712 » Fri May 26, 2006 5:47 am

what's the specific reason to have to have it negative? that too70?
ANy theoretical sights?
I think the potential must be affecting the ion exchanges by either favouring or not favouring it. If it favours then less energy will be required for the transport o/r more transport will occur. & when it resists -more energy o/r less transport.
This will affect the net cellular energy expenditure & thus efficiency of cell.
The The relative best rates & amounts of intake of different chemicals is definite. The PD would be adjusted according to relative importance of the membrane processes.
Hussh! Hope that can make some sense...

Ved

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Post by MrMistery » Fri May 26, 2006 5:24 pm

Not in my head, sorry... What you need to understand is that the membrane potential is a property of a membrane. The membrane does not create it's potential at will, and most membranes "don't even know it is there". absolutely all cells on earth have a membrane potential simply by the fact that the membrane is impermeable to negatively charged organic molecules. Research what is called the Gibbs-Donnan equilibrium
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