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I always believed to have roughly understood how voltage-gated ion channels and the creation of action potentials work: as and by single (or non-interacting groups of) membrane proteins, that behave somehow non-linearily by intrinsic means, each by its own. But suddenly I doubt.

Might it be the case that some of the non-linear dynamics of ion channels and the generation of action potentials cannot be understood when looking only at single ion channels as proteins? Or is it like Wikipedia says:

A voltage-gated ion channel is a cluster of proteins embedded in the membrane.

This means, that some of the non-linearities only occur when many membrane proteins (presumably in a fine-tuned mix of different types) interact?

Maybe only then some features of ion channels can be understood:

  • Action potentials are always of the same size, independent of the voltage (or current) that is applied/injected (which would be hard to understand for single membrane proteins).

  • Ion channels can exhibit many different firing patterns, which depend on intrinsic emergent mechanisms of assemblies of membrane proteins.

If this is so, one must be very careful when talking or reading about voltage-gated ion channels, because depending on context sometimes single membrane proteins are meant, and sometimes complex assemblies of non-linearily interacting proteins.

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Wikipedia's statement

A voltage-gated ion channel is a cluster of proteins embedded in the membrane.

is most likely referring to the fact that most ion channels (maybe all? I hate to say "all" in biology) are made up of multiple protein subunits; usually these are all considered one protein's quaternary structure, though, so wikipedia's language is not ideal.

I think you are then running with a misunderstanding of this statement to make some conclusions that are not warranted. Of course multiple ion channels come in to play when you are talking about membrane potentials at the cellular level. Of course you need to consider multiple ion channels when considering the overal membrane potential, but it is sufficient to know only a) the gating properties of a given channel and b) the membrane potential to know the contribution of that channel.

Action potentials are only roughly the same 'size' in terms of voltage amplitude - they are certainly not identical, and this size is because of the gating properties of voltage gated channels and the reversal potential for sodium. The membrane potential can never exceed the reversal potential for sodium via sodium-based conductances, so that puts an upper limit on action potential size. In addition, hyperpolarizing potassium-permeable voltage gated channels will open at depolarized potentials, further limiting the maximum amplitude of an action potential.

Ion channels don't exhibit any firing patterns: neurons exhibit firing patterns that depend on all the channels present and the physical morphology of the cell.

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