Like many little kids with wild and uninformed 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 did they think they were kidding, anyway? We all watched t.v. Some planets had monsters made entirely of lava for gosh sakes! What’s water got to do with anything?
Well. It is worth noting here that, not only is the Wondrous Human Body® a bag of sloshing fluids, it would seem the “bag of sloshing fluids” model is pretty much the only one that works to support animal life. Why? Because the metabolic processes that animate and sustain living organisms—from paramecium to blue whale—require stuff to be moved around all the needy precincts of the organism’s body.
What’s more, a living organism’s bod needs to have a strictly maintained internal environment if it’s going to be metabolically successful; or “alive”, to use the plainer adjective. Whereas the environment outside the body may be a storm-tossed and unpredictable mess, the inside of the body keeps a deliberately even keel through a maddeningly complex monitoring system called Homeostasis.
My Name is Life, and I’m a Metabolic. (“Hi, Life!”)
Homeostasis is all about maintaining a sort of environmental 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. A triptych of systems work together to announce, relay, and act upon the bad news when the system detects the internal pinball machine is beginning to tilt.
Effectors spread throughout the body (think of the high tech sensors spread around the Louvre to foil art thieves) detect when something in the internal environment is amiss, and they send a signal to a Control Center, which interprets the signal and fires off a chemical command to whatever Receptor is suited to the task of bringing everything back to equilibrium. The two main control centers, the Respiratory Center and the unlikely-sounding Renin–Angiotensin System handle, like a couple of chummy apartment superintendents, the big stuff—namely breathing and plumbing—and all the densely-packed chemical detail inherent in monitoring our respiration and our fluids. Here’s a quick and approachable example of homeostasis at work.
"Okay—Who Keeps Changing the Thermostat?!"
The Respiratory Center—which lives in the brainstem, if that doesn’t sound too plant-like — gets scattered, unceasing input from mechanoreceptors and chemoreceptors throughout the body, absorbing this info like a computer takes in data, crunching the numbers to make sure the depth and rate of breathing are normal, and that the oxygen, CO2, and blood pH levels in the body are copacetic and humming healthily along. When the environment gets stressed, the internal system raises red flags all over the place in the form of sudden hormonal changes.
These hormonal effectors fire chemical signals off to the relevant center, in this case the respiratory center. 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), which send signals to the receptor muscles. In this case, the intercostals and diaphragm, thus poked, begin doing that thing they do—and we start breathing more deeply and rapidly until the effector-markers detect chemical and hormonal equilibrium has been re-established, at which point the system returns to that cat-like purr associated in 70s-era radio ads with the Wankel Rotary Engine. Ahem.
Water and Power
The other control center, the Renin–Angiotensin System, deals with vascular pressure, fluid balance, and electrolyte levels. Your watery insides have to remain watery within a prescribed range (short and insanely simplistic version—you have to take back in what you sweat and pee out), and when in the form of blood your water can’t charge through the plumbing under such pressure that the pipes are threatened with rupture.
And of course the electrolyte balance of your slushy insides has to ensure optimum electrical conductivity—fine-tuning all the ionic (not to be confused with ironic) minutiae that control the movement of fluids within and without the cells—to very approximately paraphrase the Sgt. Peppers-era George Harrison. 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 aswim in “interstitial" water, bathed in the stuff, your tiniest component parts backstroking through your wetware like Esther Williams in an MGM swimming pool.
The myriad chemical and electrical characteristics of this “interstitial” water affect how the water moves between the cells, and through the cell walls. Your nerves and muscles are just two groups that depend on our “waters” being capably managed. Homeostasis is, 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 and certified public accountants (and all the other things we are). So, yeah. We are indeed bags of water. Between the Respiratory Center and the Renin–Angiotensin System waterworks checklist, a lot is riding on our self-monitoring machinery watching its own switchboard. Weird, isn’t it? Call it Homeostasis—or Life as We Know It.
So the next time you bend down to tie your shoe and smack your noggin on the back of the bus stop bench, remember this: you are literally a wondrous machine of such complexity as philosopher-kings never dreamed. And that smack to your fool noggin is gonna leave a mark. Isn’t humanity the best?
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