Entropy during neuronal signaling

Question

to begin with: I have some background in cognitive neuroscience, but have not intensely studied the biochemical background of neuronal signalling, so please correct me if my basic understanding is wrong.

As studying the generation of action potentials and EPSP/IPSP at synapses, I noticed that as those processes make use of the gradients, the actual signalling process works by resolving these gradients (i.e. the molecules flow without having a constant energy supply pushing them to do so). The big part of energy consumption during neural signalling is then actually needed for restoration of these gradients, transmitter reuptakes etc.

So if the above is correct, does that mean that the information "flow" in the brain is done by increase of entropy (which I intuitively understand as a increase of "unorderedness", but im not a physicist either...)? I have been told that biological systems actually want to resist the "natural" direction of entropy in that they want to keep themselves "ordered" to survive. I would have hence found it more intuitive if signalling would be acquired by an active decrease in entropy (followed by some sort of "passive" restoration). Is there any reason why that is not so? Are there other examples of signalling where that is the other way round?

Or am I just lacking understanding and messing up definitions?

Thanks for your help

Answer 1

In my view, thinking of entropy as something biological life has "wants" about is a bit mistaken. In general, entropy arguments regarding biology run into a major problem in that the interesting physical laws involving entropy required closed systems, and no biological system is closed, so it's a bit moot.

It makes more sense to think about what benefits "fighting against entropy" gives a biological organism, and I also think it makes more sense to think in terms of potential energy rather than entropy (even though they are of course related).

Neuronal signaling is best when it's rapid. By pumping ions against their gradient ahead of time, neurons establish a concentration gradient (which you can view as a decrease in entropy). This is indeed the active part. This also stores energy in the gradient, in that if a 'gate' were opened, the gradient would tend to equilibrate. Because the ions involved are charged, additional sensors in the membrane can respond to this changing electrical gradient.

I would have hence found it more intuitive if signalling would be acquired by an active decrease in entropy (followed by some sort of "passive" restoration)

I think you might be mixing up the "action" verbs here. Think about pushing a rock up a cliff or lighting a firework. If you want that rock to be a signal, it's going to be a much more dramatic signal falling down the cliff than it was pushing it up the cliff. It's going to be much more dramatic lighting off the firework rather than extracting the needed ingredients from various places and assembling them. Processes that release stored energy tend to be a lot more dramatic and "active" despite being "passive" in terms of needing to add energy (besides activation).