How did I miss this the first time around? in a 2018 article, Gretchen Reynolds informs us that our organs are signaling each other with vesicles and communication molecules that change our physiology in response to exercise. This prompts more cooperation and health benefits and explains more of our internal workings.
We think we are one organism, walking and talking and stressing about our daily schedules. Instead, depending where you put your focus, you are: a human being OR a collection of organ systems (nervous system, respiratory system, cardiovascular, gastroenterological, etc) OR a bag of organs (heart, lungs, pancreas, liver, etc) OR a system of transport tubes (arteries, veins, lymphatics, nerves, or the most recently discovered: highways in the space outside of venules in the brain, activated during sleep!) OR a packed freeway of vehicles (red cells, white cells, platelets) OR a ghoulash of chemicals (thyroid hormone, insulin, interferon, cytokines that trigger fever or attract your immune defense, etc) OR a growing number of signaling vesicles (see the article above).
The rabbit hole goes very deep, my friends. And it is glorious.