Integrating reflex, feedback, and prediction: a tiered model of physiological regulation for contemporary medical education.

Medical education traditionally presents physiological regulation through homeostatic feedback loops-reactive mechanisms that correct deviations from set points. More recently, allostatic models have emphasized the brain's anticipatory role in regulation. However, presenting these frameworks as competing paradigms creates conceptual confusion for learners. This paper proposes a unified, three-tiered model of physiological regulation that positions reflexive, homeostatic, and predictive mechanisms as complementary systems operating across different timescales. Tier 1 encompasses local reflexive responses providing millisecond-to-second protection. Tier 2 comprises systemic homeostatic feedback maintaining core variables over minutes to hours. Tier 3 involves brain-centered predictive regulation integrating cognition, emotion, and context to anticipate demands. Critically, these tiers interact hierarchically: reflexive mechanisms provide immediate protective boundaries, homeostatic systems coordinate whole-body stability, and predictive processes adjust regulatory set points in anticipation of future needs. In turn, reflexive and homeostatic mechanisms constrain predictive regulation within biological limits. This hierarchical framework provides medical educators with coherent scaffolding for teaching regulation and prepares students to understand how psychological and contextual factors influence health outcomes.