{"schemaVersion":1,"id":"en-pathway-systems-path","type":"pathway","pillar":"body","locale":"en","translationGroupId":"pathway-systems-path","slugPath":"pathways/from-an-intention-to-a-movement","title":"From an intention to a movement","shortTitle":"Intention and movement","summary":"Nine steps following a single movement, from the decision through to recovery, crossing the systems of the body. The longest pathway in this corpus, and the only one where no step has a 3D scene.","level":"intermediate","estimatedMinutes":82,"synonyms":["systems pathway","nervous system","brain","motor control","circulation","recovery"],"blocks":[{"id":"b1","type":"paragraph","content":[{"kind":"text","value":"Deciding to get up from a chair takes less than a second. Between the decision and the movement, a dozen systems coordinate, most of which are neither visible nor commanded."}]},{"id":"b2","type":"paragraph","content":[{"kind":"text","value":"This pathway follows that route, in order. It is the only one in this corpus where no step has a 3D scene — and that peculiarity is itself instructive."}]},{"id":"b3","type":"heading","level":2,"text":"What this pathway lets you understand","anchor":"what-this-pathway-lets-you-understand"},{"id":"b4","type":"paragraph","content":[{"kind":"text","value":"Three ideas structure it, and each contradicts a common picture."}]},{"id":"b5","type":"paragraph","content":[{"kind":"text","value":"The command does not only descend: it "},{"kind":"strong","value":"predicts"},{"kind":"text","value":". Sensory feedback arrives too late to correct a fast movement, which forces the nervous system to anticipate."}]},{"id":"b6","type":"paragraph","content":[{"kind":"text","value":"The nerve signal "},{"kind":"strong","value":"never"},{"kind":"text","value":" varies in size. What codes an effort is not the strength of the message but its rate, and the number of units called on."}]},{"id":"b7","type":"paragraph","content":[{"kind":"text","value":"What limits an effort is almost never what the sensation points to. Breath is not the bottleneck of an endurance effort; a muscle's fatigue is not a lack of will."}]},{"id":"b8","type":"heading","level":2,"text":"Level, prerequisites and reading time","anchor":"level-prerequisites-and-reading-time"},{"id":"b9","type":"paragraph","content":[{"kind":"text","value":"The "},{"kind":"link","value":"Locate and name","href":"/en/pathways/locate-and-name","external":false},{"kind":"text","value":" pathway is a useful prerequisite: it sets out the structures this one puts into motion."}]},{"id":"b10","type":"paragraph","content":[{"kind":"text","value":"Allow around eighty minutes. It is the longest pathway in this corpus."}]},{"id":"b11","type":"heading","level":2,"text":"The steps of the pathway","anchor":"the-steps-of-the-pathway"},{"id":"b12","type":"stepList","title":"The nine steps, in order","steps":[{"id":"e1","title":"The intention forms","summary":"The map of the organ, its real neuron count, and why most of them sit where you would not expect.","targetId":"en-mechanism-brain","estimatedMinutes":10},{"id":"e2","title":"The command leaves, and anticipates","summary":"Three regions contribute to a movement. Feedback arrives too late for a fast one: the system predicts rather than steers.","targetId":"en-mechanism-motor-control","estimatedMinutes":9},{"id":"e3","title":"The signal descends","summary":"A cell that always sends the same signal, and therefore codes intensity by rate.","targetId":"en-mechanism-neuron","estimatedMinutes":9},{"id":"e4","title":"The command becomes contraction","summary":"A chemical relay that never fails, then a calcium that lifts a lock. The missing link between nerve and muscle.","targetId":"en-mechanism-neuromuscular-junction","estimatedMinutes":9},{"id":"e5","title":"The body informs itself","summary":"The channel that says where the limbs are without looking, and says rather poorly how much force they produce.","targetId":"en-mechanism-proprioception","estimatedMinutes":9},{"id":"e6","title":"The heart opens the flow","summary":"Two circuits in series, and an equation: what training improves is volume per beat, not top speed.","targetId":"en-mechanism-heart","estimatedMinutes":9},{"id":"e7","title":"The blood delivers","summary":"Everything happens in the capillaries; the rest is plumbing. And the return poses a problem the outward journey does not.","targetId":"en-mechanism-blood-circulation","estimatedMinutes":9},{"id":"e8","title":"The lung loads","summary":"An exchange that costs no energy, and a fact that contradicts the sensation: breath is not what limits.","targetId":"en-mechanism-lungs","estimatedMinutes":9},{"id":"e9","title":"The return to balance","summary":"Effort is a constraint. What wears you down is not triggering it, it is never switching it off.","targetId":"en-mechanism-stress","estimatedMinutes":9}]},{"id":"b13","type":"heading","level":2,"text":"What to take away at the end","anchor":"what-to-take-away-at-the-end"},{"id":"b14","type":"paragraph","content":[{"kind":"text","value":"The first point is the most counter-intuitive, and it comes from step 3."}]},{"id":"b15","type":"evidence","level":"established","statement":"The signal travelling along an axon obeys an all-or-nothing rule: its amplitude does not depend on the intensity of what triggered it.","detail":"This is a founding result of neuroscience, obtained by direct recording on isolated fibres. A stronger stimulus does not produce a bigger signal: it produces more of them per second.","referenceIds":["kandel2021","purves2018"]},{"id":"b16","type":"paragraph","content":[{"kind":"text","value":"The second point rests on a delay, and it runs through the whole pathway."}]},{"id":"b17","type":"evidence","level":"probable","statement":"Movement control combines an anticipatory component, based on a prediction of the consequences of the command, and a corrective component based on sensory feedback.","detail":"The framework is supported by converging observations: adaptation to an imposed perturbation, the effects of cerebellar damage, the damping of sensations produced by one's own movements. It remains a theoretical framework, not a structure identified in the brain.","referenceIds":["kandel2021","purves2018"]},{"id":"b18","type":"paragraph","content":[{"kind":"text","value":"The third point is a correction, and it comes from steps 6 to 8."}]},{"id":"b19","type":"evidence","level":"established","statement":"What sets the intensity of breathing is the concentration of carbon dioxide, not a lack of oxygen.","detail":"This is a classical result of respiratory physiology, established by manipulating the two gases separately. Breathlessness is therefore real information that points poorly at its cause: in a healthy person, the lung keeps up.","referenceIds":["hall2020"]},{"id":"b20","type":"heading","level":2,"text":"Why no step has a scene","anchor":"why-no-step-has-a-scene"},{"id":"b21","type":"callout","tone":"limit","title":"An absence that declares itself","content":[[{"kind":"text","value":"Body Lab's scenes derive from four anatomical sources: the skeleton, the muscles, the joints and the regions of the body. None of the systems this pathway crosses appears among them."}],[{"kind":"text","value":"Three distinct reasons are spread across the nine pages, and each says which one applies: the source does not contain the tissue — nerves, vessels, lungs, heart; the scale sits far below what a mesh represents — neuron, junction, receptors; or the data exists under a licence the project cannot use."}],[{"kind":"text","value":"The "},{"kind":"link","value":"Body","href":"/en/body","external":false},{"kind":"text","value":" hub announced at launch that these systems would not be covered. The position has changed on one point: being unable to show does not require saying nothing, provided the absence is declared."}]]},{"id":"b22","type":"heading","level":2,"text":"What this pathway does not do","anchor":"what-this-pathway-does-not-do"},{"id":"b23","type":"callout","tone":"caution","title":"No assessment, no instruction","content":[[{"kind":"text","value":"These nine pages describe general mechanisms in healthy adults. None assesses an individual situation, proposes a protocol or interprets a symptom."}],[{"kind":"text","value":"A sudden disturbance of speech, vision, strength or balance, chest pain, unusual breathlessness or faintness during effort are medical emergencies: the thing to do is call emergency services, not read a page."}]]},{"id":"b24","type":"heading","level":2,"text":"Sources","anchor":"sources"},{"id":"b25","type":"sourceList","title":"Main sources","referenceIds":["kandel2021","purves2018","hall2020"]},{"id":"b26","type":"shapierAction","actionId":"parcours-energie-recuperation","label":"Follow the energy and recovery pathway","description":"Organizing effort, sleep and recovery over time happens in Shapier; Body Lab only explains why these balances matter.","webTarget":"https://shapier.app/en/parcours/energie-recuperation","appTarget":"shapier://parcours/energie-recuperation"},{"id":"b27","type":"relatedContent","title":"Read next","targetIds":["en-mechanism-nervous-system","en-mechanism-brain","en-pathway-energy-recovery-path"]}],"relations":[{"type":"prerequisite","targetId":"en-pathway-body-map-path"},{"type":"explains","targetId":"en-mechanism-nervous-system"},{"type":"next-step","targetId":"en-pathway-energy-recovery-path"}],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[{"id":"kandel2021","authors":"Kandel ER, Koester JD, Mack SH, Siegelbaum SA","year":2021,"title":"Principles of Neural Science, 6th edition","source":"McGraw Hill","kind":"book","url":"https://www.mheducation.com/highered/mhp/product/principles-neural-science-sixth-edition.html?viewOption=student"},{"id":"purves2018","authors":"Purves D, Augustine GJ, Fitzpatrick D, Hall WC, LaMantia AS, Mooney RD, Platt ML, White LE","year":2018,"title":"Neuroscience, 6th edition","source":"Oxford University Press","kind":"book","url":"https://lccn.loc.gov/2017028094"},{"id":"hall2020","authors":"Hall JE, Hall ME","year":2020,"title":"Guyton and Hall Textbook of Medical Physiology, 14th edition","source":"Elsevier","kind":"book","url":"https://shop.elsevier.com/books/guyton-and-hall-textbook-of-medical-physiology/hall/978-0-323-59712-8"}],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02","evidenceLevel":"probable"},"limitations":["No step in this pathway has a 3D scene. The systems it crosses appear in none of the anatomical sources Body Lab uses, and each page says which of the three reasons applies.","The pathway presents the steps in a linear order for readability. In a body they overlap widely and several run at the same time.","Splitting roles between brain regions is a useful simplification; those regions work together continuously.","None of these pages assesses an individual situation. A neurological, cardiac or respiratory disturbance of sudden onset is a medical emergency."],"seo":{"title":"From an intention to a movement — a guided pathway through the body's systems","description":"Nine steps from brain to muscle and back: command, signal, contraction, sensory feedback, oxygen supply and recovery.","canonicalPath":"/en/pathways/from-an-intention-to-a-movement","image":"/og/en/pathway-systems-path.png"},"app":{"offlineEligible":true},"version":1}