Hemodynamic Homeostasis · §1 · MAP = CVP + CO × SVR

Mean arterial pressure is owned by no single organ

Mean arterial pressure (MAP) is owned by no single organ: it is the hydraulic product MAP = CVP + CO × SVR. From the per-system seam variables — cardiac output 5 L/min, systemic vascular resistance 17.8, central venous pressure 4 mmHg — the resting value is 93 mmHg (error 0). The relation is forced [V]; the absolute mmHg scale is open [O].

This volume treats arterial pressure as the output of a multi-organ control loop, not as the property of any one tissue. The defining relation MAP = CVP + CO × SVR reproduces a resting 93 mmHg from the cardiac and vascular seams (error 0), so the pressure is shared, not owned; the absolute mmHg scale is left open [O] with a stated obstacle.

The defended variable is a loop output, not an organ

Arterial pressure is set by a hydraulic relation across organs, not by one tissue. The steady mean arterial pressure obeys Ohm’s hydraulic law MAP = CVP + CO × SVR, where cardiac output (CO) is contributed by the heart and lungs and systemic vascular resistance (SVR) by the arterial tree. Pressure is therefore an emergent quantity of the whole circulation, and the question “which organ sets blood pressure?” is mis-posed: no organ does, the loop does.

From the seam values CO = 5 L/min, SVR = 17.8 mmHg·min/L and CVP = 4 mmHg, the hydraulic product returns 93 mmHg with error 0 (research target RP1). The pressure is partitioned across the cardiac and vascular contributions, so the setpoint has no single owner — the share is split, and the defense of that share is what the rest of this volume reconstructs.

A grounded, DNA-based reconstruction — not a toy model

This is a mechanistic reconstruction whose nodes are grounded in real genomic physics. The identity of each control node is fixed by its master gene’s nearest-neighbour stacking parameter γ, measured directly from the human promoter sequence by the SantaLucia-1998 thermodynamic pipeline and validated against the locked DNA atlas bit-for-bit (never fitted). The slow volume integrator is the kidney node, master SIX2 (γ = 1.5556); the renin–angiotensin node is master REN (γ = 1.3634). The full derivation of node identity and developmental order lives in the DNA volume (single source of truth); this package re-measures the master-gene γ in-package and builds the multi-organ pressure loop on those grounded identities. The next section is dedicated to that genomic grounding.

What this volume establishes

On those grounded identities the package closes the CO × SVR × volume loop, reads it through two concrete molecular sensors (PIEZO1/2 stretch, NKCC2 NaCl), and reconstructs its fast and slow defense and its failure modes: essential hypertension as an integral-controller setpoint reset, chronic heart failure as a saddle-node basin collapse, and the whole family of hypotensions as a node decomposition of the same loop. Every claim carries an explicit reproducibility grade and a reproduction link, so a reader can see exactly what is reproduced, what is cited, and what is left open.

How to read the grades

The hydraulic relation and the loop shapes are sim-reproduced [V]; the master-gene identities are DNA-measured [V]; the cited resting CO/SVR/CVP, gains and clinical mortality are anchors [L]; the absolute mmHg, firing-rate, incidence and effect-size scales are open [O] with the obstacle named in the irreproducibility ledger (and separately anchored to clinical units in the calibration chapter). Reproduced shapes and directions are asserted; absolute first-principles scales are not over-claimed.