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Ever wonder what "Life as we know it" means? It sounds so limiting. Like many little kids with wild and unformed imaginations, I bridled at hearing science’s verdict on the possibility of life on other planets. “A planet would need to have water to sustain life as we know it.”
Life as we know it? Who wants that?! And who do they think they're kidding, anyway?
We all obsessively watched TV in our Roy Rogers pajamas and knew for a fact some planets had monsters made entirely of lava! What’s water got to do with anything?
Homeostasis, Water, and Life As We Know It
The metabolic processes that animate and sustain living organisms—from bacterium to brontosaurus—require nutrients and other important stuff to be moved all around a living organism’s body.
Plainly speaking, this requires a watery interior, and a river-like current along which such things can travel. Whether that "body" is a bacterium 1 µm long (a human hair is about 40 µms thick), or is a long-necked behemoth at 15 tons and 72 feet, "Life as we know it" is basically made of water.
What’s more, a living organism’s watery physical system needs to have a strictly maintained internal environment if it’s going to be metabolically successful; or “alive”, to use the plainer adjective.
The environment outside the body may be a storm-tossed and unpredictable chaos, but it doesn't matter—so long as the inside of the body maintains a placid, deliberately calm environment.
Living things -- plants and animals alike -- have evolved a crazily complex monitoring system to keep our interior weather sunny and mellow. The system is called Homeostasis.
My Name is Life, and I’m a Metabolic. (“Hi, Life!”)
Homeostasis is all about maintaining a sort of environmental metabolic normalcy inside our curiously machine-like bodies, so that the complex chemical and physical doodads in there can perform their gazillion science-fictional functions with no problemo.
Homeostasis is thus—as any regular reader of these essays would by now expect— jaw-droppingly mechanical.
When your bodily mechanics go off the rails, a bunch of systems work together to announce and act on the bad news that your internal pinball machine is beginning to tilt — and homeostasis comes roaring back in like an angry babysitter. More or less.
How does our system "know" when it's going a little haywire? It relies on a body-wide metering system; a bunch of tattletale triggers called Effectors that exist all over the body. When an effector gets triggered, systems spring into action to get all our important internal readings back into an acceptable, "normal" range.
In the case of homeostasis, one of its complex system of effectors gets activated by an internal reading that is straying from the "acceptable" range.
The particular effector sends a signal to a Control Center, which reads the signal and fires off a chemical command to whatever Receptor is suited to the task of bringing everything back into equilibrium.
Homeostasis: Your Hometown Control Freak
The two main control centers, the Respiratory Center and the musical-sounding Renin–Angiotensin System handle, like a couple of chummy apartment superintendents, the big stuff; namely breathing and plumbing.
The Respiratory Center sends out chemical commands to manage the — yes —respiratory system. The Renin–Angiotensin System manages the blood flow; namely blood pressure, blood volume, sodium reabsorption, potassium secretion, water reabsorption, and vascular tone (how wide or narrow a blood vessel can become when necessary).
Here’s a quick and approachable example of homeostasis at work.
"Okay—Who Keeps Messing with the Thermostat?!"
The Respiratory Center (RC) lives in the brainstem, if that doesn’t sound too plant-like. It gets constant input from mechanoreceptors and chemoreceptors — effectors — throughout the body.
That is, the effectors in your body’s system hear the hormonal hollering, notify the gooey gizmos located in the brainstem—the dorsal, ventral, and pontine respiratory groups (you didn’t ask, but there it is) — and these respiratory triggers then send signals to the receptor muscles.
Water and Power and Homeostasis
The other control center, the Renin–Angiotensin System, deals with the wet stuff, as we've mentioned; dialing in vascular pressure, fluid balance, and electrolyte levels. Your watery insides have to remain watery within a prescribed range. Short and simplistic version? You have to replace the water that leaves your body in the form of sweat and pee-pee. If you'll forgive the technical jargon.
Internal fluid pressure is a big deal, too. When in the form of blood, your water can’t charge through the plumbing under such pressure that the pipes are threatened with rupture.
The point of all this? Water, in all its biophysical complexity, is key to your system remaining alive.
The chemical and electrical characteristics of this “interstitial” water affect how the water moves between the cells, and through the cell walls.
You see, the 60% of you that is water doesn’t just exist within the individual cells of your body.
The cells themselves are also swimming in “interstitial" water -- the complex chemical slop in which your guts are immersed and suspended. Yeah, you're a wet mess. Why do you think surgeons wear aprons and shower caps when operating?
Bottom line? The Miracle of Life means your tiniest component parts are backstroking through your wetware like Esther Williams in an MGM swimming pool. I'm sure you know what I mean. Or your grandparents do, anyway.
Homeostasis works unceasingly to keep your inner swamp happy and balanced—a process, perhaps unsurprisingly, bolstered by certain of our pals in the plant kingdom, like Maca Root and Ashwagandha. More evidence of the interrelated nature of plants, animals, and over-caffeinated hedge fund managers.
Homeostasis and the Miracle of Humanity
So, yeah. A lot is riding on our machinery watching its own switchboard. Life as We Know It. Weird, isn’t it?
So the next time you bend down to tie your shoe and smack your head on the back of the bus stop bench, remind yourself that Shakespeare called a human being the "Paragon of animals".
That's right— you are literally a wonder, a ponderable mystery long celebrated by philosopher-kings. And that little bus bench incident is gonna leave a mark. Humanity ... it's complicated. We wouldn't have it any other way.