How does electricity flow through the body?

[somasimple]

Pumps do function. They're using energy, be it ATP (K/Na pumps) or some other reaction (COX).

You don't necessarily have a case where there's an equilibrium between electrical and concentration gradients, or any equilibrium at all. The inner mitrochondrial membrane, for instance, is not at equilibrium electrically or concentration-wise. (Although more so with respect to concentration because a certain amount of ion exchange occurs.)

1/ This kind of assertion doesn't bring any argument against my allegation. I'll bring a little drawing.
2/ I know there are many organelles that are not electrically neutral but if they aren't neutral why don't you take them into account?

 

[somasimple]

but in a living cell the concentration gradient is formed by ion pumps such as Na/K-ATPase moving ions against their concentration gradient.

http://www.ncbi.nlm.nih.gov/pubmed/9325376

Contribution of the Na+ pump to resting axonal potential is estimated at -7 mV. Ouabain (10 microM to 10 mM) evoked a dose-dependent depolarization that was maximal at >/=1 mM, depolarizing the nerves to approximately 35-40% of control after 60 min.

Not 10 seconds as stated and the contribution of Na K pump is often < to 10 % of the resting potential.

 

[Deoxyribose]

http://www.ncbi.nlm.nih.gov/pubmed/9325376

Not 10 seconds as stated and the contribution of Na K pump is often < to 10 % of the resting potential.

Did you misread my statement?

but in a living cell the concentration gradient is formed by ion pumps such as Na/K-ATPase moving ions against their concentration gradient.

Notice that I said the concentration gradient is formed by ion pumps such as Na/K-ATPase, not that the concentration gradient is formed by Na/K-ATPase.

Inhibiting energy metabolism (CN- and iodoacetate) during high-dose ouabain (1-10 mM) exposure caused an additional depolarization, suggesting additional ATP-dependent, ouabain-insensitive ion transport systems.

This does show that Na/K-ATPase is not the only ion pump involved in maintaining the resting membrane potential. It also shows that ATP is necessary to power those ion pumps.

In addition, maintenance of membrane potential is critically dependent on continuous Na+ pump activity due to the relatively high exchange of Na+ (via the above mentioned routes) and K+ across the membrane of resting optic axons.

So the membrane potential is critically dependent on Na⁺ pumps. Na⁺ pumps are ion pumps. This evidence further supports my claim that concentration gradients in a living cell are formed by ion pumps and that ion pumps are necessary to maintain resting membrane potential.

To sustain electrogenesis, transmembrane K+ and Na+ gradients maintain axons in a polarized state and provide energy for signaling, respectively. These electrochemical gradients are established by energy-dependent ion transport systems, the most important of which is the Na+,K+-ATPase

These were the second and third sentences of the introduction.

 

[somasimple]

http://www.ncbi.nlm.nih.gov/pubmed/2446906

The inward movement of sodium ions and the outward movement of potassium ions are passive and the reverse movements against the electrochemical gradients require the activity of a metabolism-driven Na+/K+-pump.

http://www.ncbi.nlm.nih.gov/pubmed/6320455

Pumped and transported components of ionic flux have been added to passive electrodiffusive components.

A plot of the membrane potential versus log [K]o with an electrogenic Na pump present gives a curve with slopes both greater than and less than 58 mV per 10-fold concentration change. Over a middle range of [K]o values, the slope is 58 mV. The slope of Em versus log [K]o curves is, therefore, not a very sensitive test for the presence of an electrogenic pump.

If pumps acts only for less than 10% what is the resting 90% made of? Perhaps, passive?

 

[somasimple]

The inward movement of sodium ions and the outward movement of potassium ions are passive
Let's describe all the events that happen simultaneously:
1/ Sodium movement balanced with chloride
sodium is inward and Na ions stick to the internal membrane
chloride ions stay out, and balance the Na charge, across the external membrane
2/ Potassium movement balanced with chloride
potassium is outward and K ions stick to the external membrane
chloride ions stay in, and balance the K charge, across the internal membrane

Now let's see what happens on each side:
1/ Internal side:
sodium is inward and Na ions stick to the internal membrane
chloride ions stay in, and balance the K charge, across the internal membrane
2/ External side
chloride ions stay out, and balance the Na charge, across the external membrane
potassium is outward and K ions stick to the external membrane
Result: a membrane voltage that is... quite null.

Osmosis:
Since there are concentrations changes there is water flux through aquaporins:
1/ from int to ext for sodium
2/ from ext to int for potassium
Result : How is it possible to make a bidirectional and simultaneous water movement in aquaporins?

 

[somasimple]

Let's take now the hypothesis where external membrane is covered by positive ions and internal one by negative ones.
The Na/K pump owns fantastic properties :
It takes out sodium while it pumps in potassium.
But... But...
It takes out sodium against a negative barrier. This negative barrier attracts positive ions.
It pumps in potassium against a positive barrier. This positive barrier reppels positive ions.
That's two major problems.

You will face to the same problems with the event of an action potential.

 

[somasimple]

http://en.wikipedia.org/wiki/Action_potential#Ion_pumps

Ion pumps influence the action potential only by establishing the relative ratio of intracellular and extracellular ion concentrations. The action potential involves mainly the opening and closing of ion channels, not ion pumps. If the ion pumps are turned off by removing their energy source, or by adding an inhibitor such as ouabain, the axon can still fire hundreds of thousands of action potentials before their amplitudes begin to decay significantly.[23] In particular, ion pumps play no significant role in the repolarization of the membrane after an action potential.[10]

 

[somasimple]

http://en.wikipedia.org/wiki/Talk:Action_potential#Ions_and_the_forces_driving_their_motion