How Do Brain and Body Regulate Each Other?

Feedback, bodily signals, hormones, and immune communication—and the evidence linking them to experience and health.

Level: Intermediate
Reading load: 10 core readings in 5 units
Prerequisites: The Biological Psychology foundation, or equivalent familiarity with neurons, synapses, and the distinction between recording and intervention. No physiology or statistics course is assumed. The longer conceptual and mechanistic reviews may need several sittings; focus on the reasoning without needing to reproduce every analysis.
Last reviewed: September 2026

Introduction

We notice the body most readily when its quiet adjustments become conspicuous: the heart races, warmth rises, or illness changes the feel of an ordinary day. These experiences invite explanation at several levels. What is being regulated? How does information pass between brain and body? What does a measurement disclose, and how do time and circumstance alter its meaning?

This syllabus connects competing accounts of regulation with bodily perception, hormonal influences, short-term responses to challenging social situations, and communication between the immune and nervous systems. Conceptual papers supply distinctions; experiments and prospective studies let you examine their consequences. The progression includes both signals from brain to body and information returning from the body, while keeping the organism's experience and social setting in view.

By the end, you should be able to separate a bodily outcome from the processes producing it, evaluate the interpretation of a physiological or perceptual measure, distinguish short-term adjustment from lasting consequences, and specify what evidence would strengthen a proposed brain–body explanation.

Unit 1 of 5

What is being regulated?

A variable can remain stable because several processes are actively changing. Begin by distinguishing the outcome from the effectors responsible for it. Ramsay and Woods compare regulatory frameworks and propose their own boundary between homeostasis and allostasis; carry that proposal forward as a position to evaluate, not a definition every later author must share.

Reading
1 of 10
Clarifying the Roles of Homeostasis and Allostasis in Physiological Regulation
Ramsay, D. S., & Woods, S. C. (2014). Clarifying the roles of homeostasis and allostasis in physiological regulation. Psychological Review, 121(2), 225–247. https://doi.org/10.1037/a0035942
Foundational argument · Critical reappraisal · Challenging · Full work: 23 pages
Compare the different explanations of stability, anticipation, and overcompensation. This establishes the vocabulary for evaluating a physiological result throughout the syllabus.
A question to consider. Two people show the same temperature after a challenge. What measurements of responses and environmental conditions would help distinguish similar regulation from different processes producing the same outcome?

Unit 2 of 5

How does the body communicate with the nervous system?

Regulation requires information, but information entering the nervous system is not automatically a conscious sensation. The roadmap separates processes and pathways; the cardiac study then asks how to measure different aspects of bodily perception. A useful conceptual distinction still needs a defensible task.

Reading
2 of 10
Interoception and Mental Health: A Roadmap
Khalsa, S. S., Adolphs, R., Cameron, O. G., Critchley, H. D., Davenport, P. W., Feinstein, J. S., Feusner, J. D., Garfinkel, S. N., Lane, R. D., Mehling, W. E., Meuret, A. E., Nemeroff, C. B., Oppenheimer, S., Petzschner, F. H., Pollatos, O., Rhudy, J. L., Schramm, L. P., Simmons, W. K., Stein, M. B., … Interoception Summit 2016 participants. (2018). Interoception and mental health: A roadmap. Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, 3(6), 501–513. https://doi.org/10.1016/j.bpsc.2017.12.004
Major synthesis · Methodological contribution · Challenging · Full work: 13 pages
Follow the path from bodily signals to sensing, interpretation, and regulation. The roadmap extends the opening framework beyond an isolated regulated variable.
A question to consider. Someone feels a racing heart during public speaking. Which observations would distinguish a faster heartbeat, greater attention to it, and a more threatening interpretation of the sensation?
Reading
3 of 10
Knowing Your Own Heart
Garfinkel, S. N., Seth, A. K., Barrett, A. B., Suzuki, K., & Critchley, H. D. (2015). Knowing your own heart: Distinguishing interoceptive accuracy from interoceptive awareness. Biological Psychology, 104, 65–74. https://doi.org/10.1016/j.biopsycho.2014.11.004
Methodological contribution · Moderate · Full work: 10 pages
Examine how the roadmap's distinctions become task scores, confidence measures, and questionnaire responses. The later critiques in the guide help separate the conceptual contribution from the limitations of particular methods.
A question to consider. A confident participant scores poorly on heartbeat–tone judgments. What would you check before concluding that the participant lacks awareness of their own accuracy?

Unit 3 of 5

How do hormones act in context?

A chemical signal does not carry one psychological meaning wherever it appears. Arnold introduces timing, receptors, and developmental history; Marlin and colleagues examine a local mechanism during the acquisition of pup retrieval. Distinguish endocrine exposure, local neural signaling, the behavior measured, and the population to which a claim is extended.

Reading
4 of 10
The Organizational–Activational Hypothesis
Arnold, A. P. (2009). The organizational–activational hypothesis as the foundation for a unified theory of sexual differentiation of all mammalian tissues. Hormones and Behavior, 55(5), 570–578. https://doi.org/10.1016/j.yhbeh.2009.03.011
Foundational argument · Critical reappraisal · Challenging · Full work: 9 pages
Track how timing and experimental comparisons separate lasting, ongoing, and nonhormonal influences. This adds developmental history to the regulatory account.
A question to consider. Two groups differ in behavior despite the same measured adult hormone concentration. Design a comparison that could distinguish an earlier exposure effect from a difference in current receptor sensitivity.
Reading
5 of 10
Oxytocin Enables Maternal Behaviour by Balancing Cortical Inhibition
Marlin, B. J., Mitre, M., D’amour, J. A., Chao, M. V., & Froemke, R. C. (2015). Oxytocin enables maternal behaviour by balancing cortical inhibition. Nature, 520(7548), 499–504. https://doi.org/10.1038/nature14402
Landmark empirical study · Challenging · Full work: 6 pages
Connect the hormone framework to a specific learning and circuit experiment. Compare the evidence about acquiring retrieval with the evidence about performing it once learned.
A question to consider. How would you test whether oxytocin changes sensitivity to pup calls, the learning produced by experience, or the ability to execute retrieval?

Unit 4 of 5

What happens during stress?

A stressor, an appraisal, a bodily response, and a health consequence are different parts of an explanation. The mechanistic review supplies pathways and timescales; the social-evaluation experiment tests how context changes several responses. Read cortisol alongside the design and other measures, rather than as a universal stress score.

Reading
6 of 10
Neural Regulation of Endocrine and Autonomic Stress Responses
Ulrich-Lai, Y. M., & Herman, J. P. (2009). Neural regulation of endocrine and autonomic stress responses. Nature Reviews Neuroscience, 10(6), 397–409. https://doi.org/10.1038/nrn2647
Major synthesis · Challenging · Full work: 13 pages
Trace the autonomic and HPA pathways and their feedback. They supply a mechanistic basis for interpreting the human experiment that follows.
A question to consider. Specify a sampling schedule that could distinguish a rapid autonomic response, a later hormonal response, and recovery after a demanding task.
Reading
7 of 10
Acute Threat to the Social Self
Gruenewald, T. L., Kemeny, M. E., Aziz, N., & Fahey, J. L. (2004). Acute threat to the social self: Shame, social self-esteem, and cortisol activity. Psychosomatic Medicine, 66(6), 915–924. https://doi.org/10.1097/01.psy.0000143639.61693.ef
Landmark empirical study · Moderate · Full work: 10 pages
Use the pathway account to interpret the timing and divergence of the measured responses. Identify the social context that was randomized and the emotional processes that were only measured.
A question to consider. What does this experiment establish about an evaluative situation, and what additional manipulation would be needed to establish that shame carries its effect on cortisol?

Unit 5 of 5

How do systems and environments interact over time?

Acute adjustment is only part of regulation. McEwen connects repeated demands and interacting mediators; Dantzer adds immune communication back to the brain; Cohen tests a prospective health association under controlled viral exposure. Together they let you ask which links in a broad explanatory chain are established and which remain plausible.

Reading
8 of 10
Protective and Damaging Effects of Stress Mediators: Central Role of the Brain
McEwen, B. S. (2006). Protective and damaging effects of stress mediators: Central role of the brain. Dialogues in Clinical Neuroscience, 8(4), 367–381. https://doi.org/10.31887/DCNS.2006.8.4/bmcewen
Major synthesis · Foundational argument · Challenging · Full work: 15 pages
Compare protective adjustment with repeated, prolonged, or inadequate responses, and revisit the opening terminology. McEwen uses allostasis more broadly than Ramsay and Woods.
A question to consider. How could both accounts describe the same repeated physiological pattern while disagreeing about its label? Specify the effector activity, outcome, and recovery measurements needed to move the debate beyond terminology.
Reading
9 of 10
From Inflammation to Sickness and Depression
Dantzer, R., O'Connor, J. C., Freund, G. G., Johnson, R. W., & Kelley, K. W. (2008). From inflammation to sickness and depression: When the immune system subjugates the brain. Nature Reviews Neuroscience, 9(1), 46–56. https://doi.org/10.1038/nrn2297
Major synthesis · Foundational argument · Challenging · Full work: 11 pages
Trace the routes by which immune activity changes brain function and behavior. This completes a reciprocal account instead of treating immunity solely as an outcome of stress.
A question to consider. A challenge produces inflammation, fatigue, and withdrawal. What timing and control comparisons would help distinguish an acute sickness response from a more persistent psychological change?
Reading
10 of 10
Psychological Stress and Susceptibility to the Common Cold
Cohen, S., Tyrrell, D. A. J., & Smith, A. P. (1991). Psychological stress and susceptibility to the common cold. New England Journal of Medicine, 325(9), 606–612. https://doi.org/10.1056/NEJM199108293250903
Landmark empirical study · Moderate · Full work: 7 pages
Bring the preceding mechanisms to a whole-person study, then identify which were actually tested. If you encountered this paper in the foundation, now evaluate the proposed chain from stress through biological susceptibility to illness.
A question to consider. Which alternative explanations are reduced by standardized viral exposure and blinded illness assessment, and which remain because stress was measured rather than assigned?

Scope and omissions

This path examines regulatory reasoning through selected neural, endocrine, immune, and behavioral examples. It is not a comprehensive physiology course: detailed anatomy, every endocrine axis, pain mechanisms, metabolism, and reproductive biology extend beyond its budget. Motivation, emotion, and sleep pose related but distinct questions.

Animal experiments, restricted human samples, and clinical comparisons support different conclusions. The readings do not establish human social roles from hormone effects, equate symptoms with a single biological cause, or offer treatment advice. Social conditions shape exposures and opportunities for recovery; biological measurement should not turn disadvantage or illness into an individual's fault.

Synthesis

Brain and body sustain an exchange across many timescales. Bodily signals affect neural activity and experience; neural, hormonal, and behavioral responses alter bodily conditions; immune activity sends information back. The consequences depend on developmental history, present circumstances, and the systems involved. A chemical or brain region earns its place in the explanation through evidence of its contribution to that exchange.

A physiological difference alone does not tell us whether regulation is effective, what someone experiences, or what caused a later health outcome. Distinguish the variable from its effectors, the construct from its measure, the immediate response from its recovery, and an experimental manipulation from an observed association. Competing frameworks become useful when they produce different comparisons or predictions.

To connect bodily need with seeking, effort, threat, and feeling, continue with How Do Biological Systems Shape Motivation and Emotion?.

Choose one biomarker difference between two groups. Offer two explanations consistent with it, then propose an intervention, repeated-measurement schedule, or contextual comparison that would separate them. Identify the psychological and biological outcomes and what the proposed study would still leave unresolved. To examine changing environments and developmental trajectories more deeply, continue with How Do Contexts Shape Developmental Pathways?.