Matt... thank you.
Jeffrey...
To what extent do these different pathways operate at a local level?
Largely, obviously; but it is the sum total that we need be concerned with... unless you are HIT training your calves doing Donkey raises.
For example, if I did ten getups, alternating sides, with no rest between them, would I be working the muscles on one side primarily within the alactic pathway, while the other side mostly rests, or would the entire body go as a unit into primarily the glycolytic pathway once my activity exceeds 30 seconds or so?
How does one side mostly rest during a get up? What is the difference between the tension directly under load, and the tension that "pulls" against the tension under load? That said, this thinking is categorical in nature, which is important for learning, but doesn't work well in actual biology. So, if your load was heavy enough, you'd be glycolytic, in your scenario. If it was light, and you're an experienced mover who was grooving, you could actually be oxidatve.
Don’t the muscles pretty much draw on their own stored energy in the anaerobic pathways?
In all pathways, but they are ongoingly resupplied through the blood.
Aerobic, on the other hand, is more total body? When running long slow distance, the body uses stored energy from any place it is available?
It's just a larger fuel tank. Alactic fuel (available ATP + CP) is stored in the cell only, and is used up very quickly. At rest, during an interval, let's say, it is replenished through the other systems. Glycolytic fuel (sugar) is stored as glycogen in the muscle and in the liver... and the liver is always making more, but this is a slow process during exercise, so this tank is "small". Oxidative fuel (fatty acids) are stored in the muscle and in adipose tissue, of which even lean people have like weeks of, when starving... a BIG tank. So, tiny tank, small tank, big tank; not local or systemic.
Intensity dictates which fuel tank is tapped more so than duration does, generally.