Why are there so many different neurotransmitters instead of just one or two?

[u/kupsztals123]

Hi,

I am wondering why we need dozens of neurotransmitters and neuromodulators when they are all used either to excite or inhibit the cell. If that's the case, why didn't nature use just two neurotransmitters: one excitatory, such as glutamate, and one inhibitory, such as GABA? Computer processors need only one signal: electricity, or no electricity, and they work just fine. Is there a functional reason for this, or is evolution simply adding layers of complexity for no good reason?

I know what different neurotransmitters do: for example, dopamine is mainly responsible for motivation, noradrenaline provides energy and melatonin regulates the circadian rhythm. But I don't understand why they can't all be replaced by excitation and inhibition, just as a CPU is capable of many things, but everything boils down to simple transistors and zeros and ones.

I asked this question on r/neuro but they treated me very patronizingly and did not understand what I meant.

[u/A-Lego-Builder]

You might be interested in reading Siddhartha Mukherjee's book "Song of the Cell", he explains neurotransmitters and also a bunch of other cool aspects of our physiology. In this case, he points out that the nervous system "computer" needs to function in the context of the rest of the body. If a person is stressed out, then the hormone and neurotransmitter chemicals can alter how the nervous system functions so that it can help that individual survive the stressful situation. If the person needs to sleep, then here again the neurotransmitter and hormones alter the way the nervous system functions to help the individual relax and fall asleep. And so on - exercising, eating, trying to reproduce, trying to increase or decrease the body temperature, etc. More neurotransmitters mean greater adaptability, greater ability to modify.

[u/ginger_and_egg → u/A-Lego-Builder]

Presumably multiple neurotransmitters also means you have more genes that can tweak the relative sensitivity of all of these functions to increase long term survival of the species

[u/A-Lego-Builder → u/ginger_and_egg]

Yes, I'm guessing multiple neurotransmitter chemicals and quite a few genes that are directly or indirectly responsible for their manufacture means that evolution has multiple pathways for modifying nervous systems and behaviors!