Homeostasis
Walter Cannon coined “homeostasis” in 1926 — from Greek homoios (similar) and stasis (standing still). The body maintains stable internal conditions despite external variation. Temperature, blood sugar, pH, hydration — all held within narrow ranges through continuous adjustment.
The mechanism is negative feedback. Deviation triggers correction. Too hot: blood vessels dilate, sweat glands activate, behavior changes (seek shade). Too cold: vessels constrict, shivering generates heat, behavior changes (seek warmth). The system detects error and acts to reduce it.
The key insight: stability requires work. A dead body equilibrates with its environment. A living body maintains difference from environment — warmer than cold air, cooler than hot air. This takes energy. Homeostasis is active maintenance, not passive equilibrium.
Claude Bernard, Cannon’s predecessor, called this the milieu intérieur — the stable internal environment that lets cells function regardless of external conditions. Fish maintain internal salt concentrations different from surrounding water. Mammals maintain body temperature independent of ambient temperature. The constancy enables life.
Homeostasis appears beyond biology. Organizations maintain cultures despite employee turnover. Markets maintain prices despite supply and demand shocks. Ecosystems maintain population ratios despite individual births and deaths.
The pattern: detect deviation, correct deviation, repeat. The stability isn’t static — it’s dynamic, achieved through constant small adjustments. The thermostat metaphor captures the mechanism: measure, compare to target, act to reduce difference.
What looks like stillness is actually continuous motion.
Homeostatic systems resist change. Push them, they push back. This is their strength (stability) and their weakness (inertia). Changing a homeostatic system requires either overwhelming the correction mechanisms or changing the setpoint itself.
Disease is sometimes homeostatic failure. Diabetes is failure to regulate blood sugar. Fever is the setpoint deliberately raised to fight infection. Addiction hijacks reward homeostasis, resetting “normal” to require the drug.
Organizations can be homeostatically stuck — every attempt at change triggers correction that restores the prior state. Culture, incentives, and habits form the feedback loops that maintain what exists.
Go Deeper
Books
- The Wisdom of the Body by Walter Cannon (1932) — Cannon coined the term and explored its mechanisms. Readable classic.
- An Introduction to the Study of Experimental Medicine by Claude Bernard (1865) — Bernard’s milieu intérieur preceded homeostasis.
- Thinking in Systems by Donella Meadows — Homeostasis as negative feedback applied broadly.
Essays
- Cannon’s original 1926 paper defining homeostasis in Physiological Reviews.
- Hans Selye’s work on stress and the General Adaptation Syndrome extended homeostatic thinking.
Related: [[feedback-loops]], [[antifragility]], [[slack]], [[maintenance]]