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Physiology and the whole organism  ·  Article

Homeostasis and the internal environment

Homeostasis is the maintenance of stable conditions inside an organism despite change outside it. Claude Bernard called the inner fluid medium the milieu intérieur and treated its constancy as the condition of free and independent life.2 Later authors define homeostasis as regulation of body fluid composition,6 and Levin proposes it as the origin of goals and cognition.5

Earliest held
1908, Washburn, M. F.
Most discussed in
Technological Approach to Mind Everywhere: An…, 2022
In the library
207 passages in 46 works
Rewritten
2026-10-03
18501875190019251950197520002025Lotka, A. J., 19251Bernard, C., 19572Bernard, C., 19573Lyon P, 20154Levin M, 20195McMillen P, Oudin MJ, Levin M, Payne SL, 20216Levin M, 20227Ciaunica A, Shmeleva EV, Levin M, 20238Levin M, 20259
01

Bernard's internal environment

It says a few scattered observations on the composition of blood were enough for him to call that constancy the condition of free and independent life.2 In his own text, Bernard argued that physicists and chemists working on inert bodies need consider only the external environment. Physiologists, he said, also need to measure the internal one. He named the circulating liquids, the blood serum and the intra-organic fluids as its parts.3

02

Independence from surroundings

Lotka (1925) took up Bernard's point in Elements of Physical Biology. He wrote that the independence an organism shows toward its remote environment increases as one ascends the biological scale. He said it is matched by a parallel increase in the perfection of the apparatus that earns it.1 Lotka quoted Bernard to the same effect. Higher organisms are freed more completely from outside change, while in invertebrates the independence is only relative.1

03

Cells, microbes and definitions

Lyon (2015) argued that bacteria monitor their surroundings and judge the significance of signals against their own functioning, their internal milieu. The passage adds that the power spectrum of signals remains unknown for any bacterium.4 Ciaunica, Shmeleva and Levin (2023) give a textbook definition from Martin and Hine (2000). Homeostasis is regulation of the chemical composition of body fluids so that physiological processes run at optimum rates.6 They set it beside Maturana and Varela's autopoiesis and the later notion of allostasis.6

04

Setpoints and anatomy

Levin (2019) proposes that homeostasis is the atom of a cognitive hierarchy. Setpoints of subcellular circuits are, in this account, the first small examples of goal-seeking systems.5 McMillen and colleagues (2021) state that bioelectric signaling is more than a physiological homeostat, because it also instructs proliferation, differentiation and apoptosis.7 Levin (2025) extends the idea to anatomical homeostasis, the return to a region of morphospace despite deviations. He makes this conditional on accepting the evidence for setpoints.8 Levin (2022) adds that this stability applies to overall anatomy, not to cell-level detail.9

SourcesEach quotation was checked word for word against the passage it opens.
  1. The increasing independence, as we ascend the biological scale, which the organism displays toward its more remote environment, is thus accompanied by a parallel increase in the perfection of the apparatus by which this independence is earned.Lotka, A. J., 1925 · Elements of Physical Biology · open at passage 110
  2. the constancy of the internal environment {milieu interieur) is the condition of free and independent life.Bernard, C., 1957 · An Introduction to the Study of Experimental Medicine · open at passage 12
  3. The circulating liquids, the blood serum and the intra-organic fluids all constitute the internal environment.Bernard, C., 1957 · An Introduction to the Study of Experimental Medicine · open at passage 205
  4. Like all organisms, bacteria do not gather information in a vacuum, but are able to assess the significance of the signals they receive relative to their own functioning, their internal milieuLyon P, 2015 · The cognitive cell: bacterial behavior reconsidered · open at passage 20
  5. This homeostatic persistence is the origin of cognitive goals – the setpoints of subcellular biochemical circuits that react to perturbations in a way that maintains parameter range are the first, tiny examples of integrated goal-seeking systems.Levin M, 2019 · The Computational Boundary of a "Self": Developmental Bioelectricity Drives… · open at passage 38
  6. bioelectric is not merely a physiological homeostat, but plays instructive roles in cell proliferation, differentiation, and apoptosisMcMillen P, Oudin MJ, Levin M, Payne SL, 2021 · Beyond Neurons: Long Distance Communication in Development and Cancer · open at passage 7
  7. Biology reaps the benefits of both types of strategies by implementing anatomical homeostasis that coarse-grains robustness by making stability applying to large outcomes, such as overall anatomy, not to the microdetails of cell states.Levin M, 2022 · Technological Approach to Mind Everywhere: An Experimentally-Grounded Framework… · open at passage 102
  8. Homeostasis is defined as “the regulation by an organism of the chemical composition of its body fluids and other aspects of its internal environment so that physiological processes can proceed at optimum rates.Ciaunica A, Shmeleva EV, Levin M, 2023 · The brain is not mental! coupling neuronal and immune cellular processing in… · open at passage 9
  9. First is the notion of anatomical homeostasis: the ability of systems to reach and maintain a specific region of anatomical morphospace despite deviations.Levin M, 2025 · The Multiscale Wisdom of the Body: Collective Intelligence as a Tractable… · open at passage 31
Linked ideas
Levin treats homeostatic setpoints as the first, smallest goals, so homeostasis is the base of goal-directed behaviour in his account.
Anatomical homeostasis supplies the setpoint idea: the body error-corrects toward a stored target form, not just a scalar such as pH.
Regenerationpart of / contains
Levin cites regrowing a correct limb wherever it is cut, and stopping when done, as organ-level homeostasis.
Basal cognitionrelated to
Single-cell homeostatic loops, such as pH control, are offered as low-level goals from which larger cognitive capacities scale.
Cell-level homeostatic loops are said to combine into organ-level loops through networks of cells.
Evolvabilityrelated to
Robustness to perturbation, as in Biswas et al.'s network memory, concerns keeping function under disturbance, which is the area homeostasis covers.
Rottenberg describes glycolytic ATP being used to hold mitochondrial membrane potential at a functional level when the electron transport system falls short.
Scale of the selfpart of / contains
Passages treat homeostasis (cellular Vmem, pH cycles, anatomical limb regeneration setpoints) as the regulatory mechanism whose scaling via bioelectric networks defines a larger self's goal-pursuing boundary.
Loeb's balanced solutions describe a stable salt ratio in ocean, blood and lymph that protects organisms, which resembles a constancy of the internal medium.
Ion channels and pumpspart of / contains
Ion channels are the hardware implementing homeostats: Levin says voltage-gated channels form feedback loops implementing memories and homeostats; Fields and Bongard say the same channels serve cell homeostasis and anatomical setpoint control.
Passages tie both to Levin's bioelectric framework: resting potentials guide embryogenesis and cancer suppression, and homeostasis in single cells scales up to cognition; Chernet shows voltage controlling oncogene-driven tumours.
Passages treat planarian anatomical homeostasis as a rewritable pattern setpoint, with goal states encoded bioelectrically and two-headed forms persisting through regeneration, a memory-like trait. They never explicitly link it to behavioural memory.
McMillen and colleagues describe membrane voltage as both a homeostat and an instructive signal.
Lyon describes bacteria judging signals against their own internal milieu.
Self-regulation is a physical account of the ordering that vitalists attributed to a special principle.
Yield and efficiency of the chain are components of how a cell keeps its energy supply steady.
Fields and Levin contrast machines that hold fixed setpoints with reconfigurable biological hardware that supports diverse goal states.
Kaludercic and Giorgio frame ROS effects as a balance between formation and removal, with damage when antioxidant capacity is exceeded.
Gap junctionsrelated to
Passages tie them via gap junctions in homeostatic plasticity (pancreatic beta-cell insulin control) and planarian anatomical homeostasis regulated by bioelectric signaling through ion channels and gap junctions (electrical synapses).
Durant et al. say planarian anatomical homeostasis is regulated by ionic and neurotransmitter signaling circuits, and Fields & Levin say neural systems reuse preneural ion-channel, electrical-synapse and neurotransmitter machinery. So B's signaling is a mechan
Where it is discussedPassages matching homeostasis, internal environment, milieu, homeostatic
2022Technological Approach to Mind Everywhere: An Experimentally-Grounded Framework… · Levin M27
2019The Computational Boundary of a "Self": Developmental Bioelectricity Drives… · Levin M24
2023Darwin's agential materials: evolutionary implications of multiscale competency… · Levin M12
2024Horizontal mitochondrial transfer as a novel bioenergetic tool for mesenchymal… · Iorio R, Petricca S, Mattei V, Delle…11
2022Competency in Navigating Arbitrary Spaces as an Invariant for Analyzing… · Fields C, Levin M11
2019Neural control of body-plan axis in regenerating planaria · Pietak A, Bischof J, LaPalme J…9
2023Bioelectric networks: the cognitive glue enabling evolutionary scaling from… · Levin M8
2020Mitochondrial Metabolism in Astrocytes Regulates Brain Bioenergetics… · Rose J, Brian C, Pappa A, Panayiotidis…7
2022Bioelectric Dysregulation in Cancer Initiation, Promotion, and Progression · Sheth M, Esfandiari L6
2015Alkaliphilic Bacteria with Impact on Industrial Applications, Concepts of Early… · Preiss L, Hicks DB, Suzuki S, Meier T…6