When a hurricane gets over land and loses the warmth of the sea, it fizzles out. With no energy, the once-organized pattern decays and pretty soon the dwindling vortex isn’t much more than a front of rain clouds.
Living organisms have the advantage here: they will take steps to keep their patterns intact when the environment challenges them. The word for this is homeostasis. If you’re not familiar with the term, here’s Merriam-Webster’s definition:
A relatively stable state of equilibrium or a tendency toward such a state between the different but interdependent elements or groups of elements of an organism, population, or group.
All living things strive to reach an agreement with their surroundings, a tendency toward the equilibrium state as the dictionary says.
Since stability is a requirement for life, living organisms developed many ways of guaranteeing they stay that way. Mammals, including humans, come with seriously impressive equipment for this purpose. Nearly any value you can name, from your heart rate, blood pressure, breathing, eye-blinks, pupil dilation, digestion, and toe-nail growth, has some kind of oversight to keep it in line with the body’s specifications.
All of these life processes have an ideal value, called a set point, and a whole mess of regulatory feedback loops work to keep bodily functions more or less at that ideal point. Like a thermostat, as soon as the number falls off the target, the feedback loop kicks in and nudges it back in place.
What is optimal for a biological function? Can we have a blood pressure, a heart rate, or toe-nail growth that is optimal regardless of the circumstances? Not likely. Set points are more like set ranges, with multiple ideal points depending on what’s happening with everything else. Ideal while staring at your cubicle’s wall is different from ideal while you’re asleep or sprinting at top speed.
More and more research reveals that biological stability, which we’re inclined to think of as specific, hard numbers, isn’t really all that stable. Regulation of life-processes involves huge amounts of communication between organs and tissues. Your body is a vibrant ecosystem, a web of interlocking networks, where each biological function relies on the activity of everything else. Any single life process, from a single cell and on up the scale of organization, results from dozens, hundreds or even thousands of signals working to create the appearance of stability.
Bruce McEwen, endocrinologist and stress researcher at Rockefeller University, suggests that this chaotic system-wide process of equilibrium-seeking ― called allostasis ― describes living beings more accurately and completely than homeostasis.20
What if the hurricane, once over dry land and risking imminent decay into rain showers, could intervene by changing its wind speeds, conserving the energy it already has, and taking a dozen other steps to move back out to the ocean?
According to the allostatic model, biology is inherently noisy and fuzzy, and this instability is actually a feature of the system. Living bodies can react in ways that a dumb storm can’t, and this considerable adaptability is possible precisely because complex systems aren’t locked into orderly machine-like processes. Allostasis is stability through
change, the flexibility that living organisms need to survive.
The brain is loosely in charge of this nightmarish bureaucracy, although it isn ft exactly a pointy-haired micro-manager. The brain works like the guy on TV who spins the dinner plates on top of dowels. Once they’re all spinning, it’s all a matter of fine-tuning and adjusting to keep the act going.
Instead of spinning plates, your brain juggles heart rate, blood pressure, hormone levels, temperature, and about ten trillion other things at once. It’s well-equipped for this job and does it beautifully (most of the time).
All of this means we need to have a hard look at our older ideas on stress. Hans Selye believed that chronically-stressed critters were pushed away from their “set point” of health when critical tissues and glands were exhausted. What Selye couldn’t know at the time is that the stress-response involves more than a simple elevation of stress hormones.
When a car almost hits you on the way home, or you have to run from a lion, your whole system gets thrown out of balance and then works to bring you back into equilibrium. The nervous system sets off a cascade of changes, starting with a snap to attention, jittery nerves, and increased heart rate that we call the adrenaline rush.
“Adrenaline rush” is deceptive wording. Where Selye viewed the “alert” feeling as the product of sympathetic nerves and adrenal hormones, allostasis implies that your entire body shifts into a different mode. When a heckler throws a beer bottle at the stage, the guy balancing the spinning plates has to react if he doesn’t want his act to end. He’s got to concentrate and stay more alert, ready to move.
While in stress-mode, organs and tissues behave differently. For a brief period of time, long enough to dodge a bad driver or get away from a lion, this is fine. But you aren’t meant to spend your life in that condition.
The allostatic model of stress suggests that stress-induced illness isn’t a result of depleting or exhausting any particular glands or hormones or what have you, but rather the unintended consequence of an overactive coping strategy. Stress-mode is not a healthy place to be, thanks to all the physiological changes it involves, and spending too much time there accumulates wear and tear across your entire body, which we measure as allostatic load. Paraphrasing researcher Robert Sapolsky, your body’s army doesn’t run out of bullets; it spends so much on the defense budget that it doesn’t have any cash left over for the more essential life processes.21
If the brief dip into stress-mode is adaptive ― that is, if it solves the problem ― then you’re fine. You’ll adjust and everything settles back to normal. It’s when you stay in stress- mode all day every day, for weeks and months, that you develop real health issues.