A detailed walk through the potassium gradient of the nerve cell — from the Nernst equation to the channels that never fully close — together with the EU claim on potassium and the nervous system, quoted in its exact wording.
A nerve cell membrane separates two fluid compartments with very different compositions. Potassium sits at a concentration many times higher inside the cell than in the surrounding fluid; sodium behaves in exactly the opposite way. This uneven distribution isn’t a matter of chance — it’s continually maintained against the natural pull toward equalization by carrier proteins in the membrane.
| Ion | In the Cytosol | In the Fluid Outside |
|---|---|---|
| Potassium (K+) | approx. 140 mmol/l | approx. 5 mmol/l |
| Sodium (Na+) | approx. 12 mmol/l | approx. 145 mmol/l |
Carrier proteins work at nearly every cell membrane, moving potassium into the cell and sodium out of it — against each ion’s own concentration gradient and at a cost in energy. Without this ongoing work, both ions would gradually even out across open channels, and the electrical basis for every nerve signal would be lost.
Consider a membrane that lets only potassium through: a particular voltage sets in — the one at which the outward-pushing concentration gradient and the inward-pulling electrical field exactly cancel each other out. This voltage is called the equilibrium potential, and it can be approximated with the Nernst equation.
EK = (R × T ⁄ z × F) × ln ([K+]out ÷ [K+]in)
Plugging in the concentrations from the table in the previous chapter gives potassium an equilibrium potential of roughly −90 millivolts. The measured resting potential of a nerve cell falls in a similar range, because at rest it’s mainly potassium channels that stand open, so the membrane tracks the potassium equilibrium closely.
“Potassium contributes to normal functioning of the nervous system”
EU-authorized wording · Regulation (EU) No 432/2012
A single nerve signal lasts only a few milliseconds, but it follows a fixed sequence in which different potassium channels each take on their own role.
Once a stimulus reaches a certain threshold, voltage-gated sodium channels open first, and the membrane briefly takes on a positive charge. This phase moves very quickly and sets up the next step.
With a small delay relative to the sodium channels, voltage-gated potassium channels open. Potassium flows out of the cell along its gradient, and the membrane voltage moves back toward its negative starting value. Without this delayed outward flow of potassium, the cell would stay stuck in its positively charged state.
As long as the voltage-gated potassium channels are still open, the membrane stays more negatively charged than in its usual resting state — a brief overshoot sometimes called afterhyperpolarization. During this window, the refractory period, the cell can’t be excited again, or only with a markedly stronger stimulus. This short window makes sure a signal travels along the nerve fiber in only one direction, instead of catching up with itself.
Alongside the voltage-gated channels just described, there’s a second group that works independently of the momentary voltage: the two-pore domain potassium channels, or K2P for short. They stay partly open at all times and produce a steady, quiet outward flow of potassium — a so-called leak current.
This leak current shapes the resting voltage even before a stimulus arrives. The more K2P channels are open in a given cell, the closer its resting voltage sits to the potassium equilibrium potential from the previous chapter. Only the interplay of a constant leak current, the delayed outward flow of potassium after a signal, and the underlying concentration gradient explains why potassium has been studied scientifically in the area of the nervous system.
“Potassium contributes to normal functioning of the nervous system”
EU-authorized wording · Regulation (EU) No 432/2012
The reference intake the EU uses for potassium in food labeling is 2,000 mg per day. Sweet potatoes, white beans, dried apricots, and spinach are among the foods that provide meaningful amounts; a varied diet generally covers this value without any additional supplement.
Its subject is electrical signaling running its physiologically ordinary course in a healthy adult whose potassium intake is otherwise adequate. The sentence says nothing about any other part of everyday life — such topics fall outside the reviewed text.
No. The Nernst equation, voltage-gated potassium channels, the refractory period, and K2P channels are scientific background that explains why the claim was reviewed in the first place. None of these structures is mentioned by name in the official wording itself.
The text addresses adults as a whole, without singling out any particular decade of life. Different considerations may apply for children, pregnant women, or people with a diagnosed kidney condition — those belong in professional hands.
Through a varied diet of plant and animal foods, as covered in the previous chapter. Anyone using a dietary supplement should stick to the amount stated on the package, especially with known kidney problems, since these affect how potassium is cleared from the body.
Includes all four chapters on this page, the tables on ion concentration and daily intake, and the full text of the EU regulation on potassium.
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