How don't neurons get enough K+ to balance out their inner negative charge?

[somasimple]

Hey man. It is not because English is not my first or native language that you have the ability to say it's rubbish.
you must examine sentences. They contain facts or arguments. You must reply with scientific arguments that contradict the previous without any "ad hominem" allegation.

Make a simple drawing with some charges and try to compute the needed forces that may answer the hypothesis.

 

[Pythagorean]

You should take your advice and try the calculations out. I happen to have done it already as a homework assignment in molecular neuroscience. As I've already suggested, you may be overestimating how much Na leaves the cell, which was the instructor's point in assigning us that particular problem.

 

[somasimple]

... which was the instructor's point in assigning us that particular problem.

Some instuctors' points come from: Nelson, Johnston, Kandel, Nilsson , Sten-Knudsen ...

The important thing is not to stop questioning. Curiosity has its own reason for existing. One cannot help but be in awe when he contemplates the mysteries of eternity, of life, of the marvelous structure of reality. It is enough if one tries merely to comprehend a little of this mystery every day. Never lose a holy curiosity.

We are still in the example of the book with a single K⁺ problem.
As it is expected, as the concentration (of the most concentrated side) grows, the voltage across the membrane must grows because a capacitor will get its voltage growing as the charge density grows.

In the above example the concentrations numbers are 155/4 and it gives 93 mV.
Try with 15.5/0.4 or 310/8 or 75.25/2 and you'll find 93 mV. In fact, there is a lot/infinity responses.
Thus you have a voltage that remains constant where the charge density may vary at will.
A capacitor dos not allow such a thing.

 

[Pythagorean]

In the above example the concentrations numbers are 155/4 and it gives 93 mV.
Try with 15.5/0.4 or 310/8 or 75.25/2 and you'll find 93 mV. In fact, there is a lot/infinity responses.

Thus you have a voltage that remains constant where the charge density may vary at will.
A capacitor dos not allow such a thing.

In the resting state (the polarized state) there needn't be capacitance. The capacitance is a term in the differential equation pertaining to the change in membrane potential. If the change is 0, then capacitance doesn't matter; see a simple neuron model

But I don't see how that has anything to do with your previous claim about the pumps (which rely on ATP) not functioning.

 

[somasimple]

In the resting state (the polarized state) there needn't be capacitance. The capacitance is a term in the differential equation pertaining to the change in membrane potential. If the change is 0, then capacitance doesn't matter; see a simple neuron model

Really?
http://www.neurophysiology.ws/membranepotentials.htm

Because the membrane behaves as if it were in part composed of parallel capacitors, we are interested in the rules governing parallel capacitors

 

[Pythagorean]

Really?
http://www.neurophysiology.ws/membranepotentials.htm

Yup!

Capacitance is only important to the dynamics. Once you are sitting still, it's just a charge distribution. If the charges must flow an indirect route, the system experiences a delay (characterized by the time constant) and your system can "jiggle" or propagate waves (since it's parallel capacitors, it's a spatial extension).

Parallel capacitors are like a mattress of springs. Springs only really function as springs if you perturb the mattress (like knocking over a wine glass at one end by jiggling the other end). If nothing ever changes, it's no different than a rigid body.

 

[somasimple]

Not yup!
If the resting potential is not null then the capacitor is charged.
If a membrane capacitor contains a charge, it comes from concentrations across the membrane but a capacitor has one and only one mathematical solution to find this voltage where I'm able to find tons.

Since I'm able to create conditions where I find a lot of solutions where I'm commonly used to find only one, I must reexamine the problem: The theory is false and/or the facts are false.

 

[Pythagorean]

Yes yup! A charged capacitor is only a meaningful concept if it's sometime going to discharge or if it got charged in the first place, which each require state evolution through time; additionally, each are separate states that are separated by time.

Also, you are imagining a single engineered capacitor with a (mostly) constant capacitance?

Here, we have a thing who's capacitance does change slightly at different membrane potentials, but because of the parallel distribution of capacitors and leak channels, the effective capacitance changes very little. Most of the change comes from the charge reshuffling (i.e. leak channels and ion pumps). Because of the parallel nature of the capacitors and the escape routes available, we can get huge fluctuations without changing the capacitance much (so the dQ mostly makes up for the dV, the small fluctuations in the capacitance are considered insignificant) . Think about a population of channels and capacitors with some distribution across the membrane, not just one set.

 

[somasimple]

(Not yup)²,

It does not change anything about the membrane potential computation.
You must explain how it is possible to get a same result with different charges densities that come from concentrations?

It is a violation of Thermodynamics: You may obtain a lesser voltage with less charges, not the same one.

 

[somasimple]

If I remove the limitations about concentrations that exist in the original form of the Nernst equation, I will be able to create/produce batteries with very few quantities of chemical products. They would be cheaper and I do not understand why manufacturers haven't thought about this simple fact.

Perhaps there is some fate in Electro-Chemistry that may not exist in Biology?

 

[Pythagorean]

You must explain how it is possible to get a same result with different charges densities that come from concentrations?

It's already been explained; you just haven't absorbed it yet. Give it some time; think about a sea of coupled capacitors with current pathways of mixed species all over and adjustable resistors changing dynamically. It's not a pretty picture that can be understood by the Nernst equation or a simple capacitor. Capacitance is a property of many different arrangements of matter; engineered capacitors are a very specific case of capacitance. And remembrer the capacitance isn't constant, it's approximately constant.

Charge accumulation and distribution isn't as straightforward with ions in a cell as it is with electrons in an engineered capacitor.

 

[somasimple]

It's already been explained; you just haven't absorbed it yet.

I may be blind or something else since I'm unable to find the sentences where you gave the results.

Charge accumulation and distribution isn't as straightforward with ions in a cell

I agree totally because I know that the cytoplasm is a gel but your talk contradicts the HH model where ions cross the membrane instantaneously and now the model of diffusion becomes... dubious.
Did you say... rubbish?

 

[Pythagorean]

I was calling your constant knit-picking and subject changing rubbish, not your confusing model with reality.

The HH actually models delays well compared to say, the Morris Lecar model, which is still a good approximation for many questions (and was derived empirically from the barnacle giant muscle fiber).

 

[somasimple]

not your confusing model with reality.

Reality: Is cytoplasm a gel?
Reality: Do diffusion cited in the book was meant to function with gel?
Reality: Does a pump function against a gel?
Reality: How Na+ ions enter the cell gel?

Etc...

How may I be confusing a model since I cite only pieces of... books and papers?
Put together, you get effectively a confusing model and the model stop to work.

 

[Pythagorean]

There is no panacea

 

[somasimple]

If the change is 0, then capacitance doesn't matter; see a simple neuron model

The HH actually models delays well compared to say, the Morris Lecar model, which is still a good approximation for many questions (and was derived empirically from the barnacle giant muscle fiber).

Perhaps I'm confused within a model that contains dozen of mistakes, wrong facts and wobbly theories. It seems somehow, perfectly logical.

But if you suppose that I will accept a neuron model that was empirically derived from a barnacle muscle fiber then I'll hypothesize you're lost in yours (models).

 

[somasimple]

There is no panacea

I'm sorry you lost any curiosity.

 

[Pythagorean]

Let me know when you fix everything that's wrong with science. I'll be here in this thread, holding my breath.

 

[somasimple]

A better model is still possible but I'm quite sure you're not interested.

 

[Pythagorean]

Nope; a better skill for my work is being able to use the right model for the right question. You could spend months on a better model and it will likely give the same result for the kinds of questions it's being used for.

There are people that go yet even simpler than Morris-Lecar but their purpose is to study synchronicity in a million neuron network. Time delays you are worried about are not important to them. It's the same for HH.

To take your argument to absurdity, why not just model neurons as an ensemble of quantum particles. Or... Why ignore the system effects of astrocytes or the underlying genetic expression?

You only focus on electrochemistry because that is apparently your area. But choosing that view skews you from other perspectives.