Why do certain NTs, sticking with Acetylcholine, produce certain results? For example, why does Acetylcholine specifically affect cognition etc? Is the process and thus the result on human experience different from other NTs?
To date, scientists have discovered 60 distinct neurotransmitters working in the brain, but of course,
acetylcholine and
GABA being the most discussed. Some neurotransmitters are inhibitory (induce a relaxing effect), while others are excitatory (encourage the target cell to take action). A target cell can be innervated by more than one type of neuron at the same time that do opposite things. Acetylcholine can react with many target neurons and non-nervous cells, including muscles that induce contraction; when acetylcholine is decomposed, the muscle relaxes. Therefore, acetylcholine plays a role in
excitation at the neuromuscular junction, but has
inhibitory actions at certain smooth muscles and at cardiac muscle.
Why acetylcholine was supposedly chosen to be part of the cognition/memory is something I'm not sure about. Maybe understanding its evolution, or the evolution of the receptors that are responsive to it would help. There's a section on Wikipedia that discusses its evolution:
Comparative biology and evolution
Acetylcholine is used by organisms in all domains of life for a variety of purposes. It is believed that choline, a precursor to acetylcholine, was used by single celled organisms billions of years ago for synthesizing cell membrane phospholipids. Following the evolution of choline transporters, the abundance of intracellular choline paved the way for choline to become incorporated into other synthetic pathways, including acetylcholine production. Many of the uses of acetylcholine rely on its action on ion channels via G-protein-coupled receptors (GPCRs) like membrane proteins.
The two major types of acetylcholine receptors, muscarinic and nicotinic receptors, have convergently evolved to be responsive to acetylcholine. This means that rather than having evolved from a common homolog, these receptors evolved from separate receptor families. It is estimated that the nicotinic receptor family dates back longer than 2.5 billion years. Likewise, muscarinic receptors are thought to have diverged from other GPCRs at least 0.5 billion years ago. Both of these receptor groups have evolved numerous subtypes with unique ligand affinities and signaling mechanisms. The diversity of the receptor types enables acetylcholine to create varying responses depending on which receptor types are activated, and allow for acetylcholine to dynamically regulate physiological processes.
https://en.wikipedia.org/wiki/AcetylcholineHope that provides more insight
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