Brain function is more than about structure - shape, what hooks to what. The brain has streaks of flavors, like the fudge in fudge ripple ice cream. There are sequences of pathways that share common chemistry. So the how is as important as the what and the where. There are many neurotransmitters.

Cholinergic
Acetylcholine is the transmitter. Basal forebrain and sympathetic tracts are cholinergic. Anticholinergic drugs (blockers) cause amnesia (scopolomine) and are used for that purpose in surgery (if you feel pain you won't remember it). Some are suspicious that Alzheimer's memory loss follows the decline of this pathway.

DOPAminergic
Oooh...do it again...oooo again.... addiction lives here. Somehow rewards behavior. Maybe this is how we crawl out of bed at 4:00AM to feed animals. The part of the brain that KNOWS this is necessary treats the suffering part with a nice DOPA jolt.

Drugs that bypass behaviors and don't need a reason just do the same thing. Ready for this? They found a gene common to alcoholism, drug addiction of several kinds, GAMBLING, and the like.
Nucleus accumbens, and the prefrontal cortex are involved as is the arcuate nucleus which tweaks the pituitary and the ventral tegmental area. Go figure. Oooo. Go figure again. Oooooo again.  Ooooagain.....

Noradrenergic
nucleus (or locus) coeruleus is the big player that uses norepinephrine. So like epinephrine in general, arousal and vigilance circuits are a good bet. Too little - depression. Too much - panic. Just right, attention and cognition. A discovery that this is deficient in Rett syndrome has led to mouse testing along these lines.

But two chemical transmitters account for nearly 90% of all neurologic activity, the two big G's:
Glutamine  is a major do-it transmitter. It's receptor is NMDA a five slat barrel or funnel through the cell membrane. Glutamine by opening the NMDA opening, says go. Do something. Glutamine is associated with stimulus. Action.

Gamma amino butyric acid (GABA) is the counterpart - it is the nervous system chief inhibitor. It asks if you're sure about this, hesitates, holds back. It has two distinct cell pore mechanisms (A&B) that let chloride through. One is a 5 slat barrel like funnel through the membrane. The other looks like the Loch Ness monster with seven loops through the membrane 3 of which crowd each other to create a pore. Technically GABA is an 'amino acid' but the amino part is two steps away from the acid part and gets disqualified from playing in any reindeer games of protein building etc.

Baclofen acts like GABA for the second cell pore type (B)

glutamate has two ways of being produced. One is the Kreb's cycle. The other is a neuro localized method. The neuron releases glutamate which is gobbled up  by key astrocytes (which have glutamine synthetase) which is where the glutamine is actually made. GABA can be made from this in neurons whose purpose is inhibition. So the good Kirk and the bad Kirk. On breakdown things go to succinate which the astrocyte uses to complete the cycle.

Now we know that the cell pores that look like sea dragons _/\/\/\/\/* drop something from their tail end after they eat (the stimulus, in this case GABA). That poop is a GTP driven first step of sever that leads to something being made in the cell. (In non neurons - say maybe insulin?). So this is the quickie zap with ions membrane voltage sparky watts thing.

We know that the vagus nerve has its chemistry and that same chemistry seems amiss in autism, or at least is the chemistry used in the autistic manner of action. So hearing sensitivity and odd ultra linear thinking get linked. Shared deep mechanisms explain how seemingly unrelated things are linked.

It is best to use books for this. A stepwise movie on brain anatomy and chemistry will exceed your life expectancy. Read the stuff that YOU require or would know more of. More models with long pathways are coming.

I am putting the EXPECTATION movie (about walking) in this section. Why? To emphasize the neurointeractive nature of it. Please, pleeeeeeeeeeezzzzzzzzzeeee, stop with this range of motion or strength nonsense. It is about TIMING and fine tuning actions to momentum and the knowing in an expectant way. Timing & correction on the fly. A deep neurologic process as deep or deeper than thinking about how to weasel a second serving of dessert from Mom. Not strength, finesse.

Movies

Pavlov NMDA

Brain Surface

Brainstem Nuclei

Expectation