Circadian Master Clock (SCN-anchored)

The circadian master clock is the τ-categorical hierarchical limit (terminal object) of the diagram of coupled cellular Poincaré orbits in a multicellular consumer carrier: a single phase-locking pacemaker — anatomically the suprachiasmatic nucleus in mammals — that receives the photic zeitgeber and entrains every peripheral cell to a common τ¹-rotation.

Categorical invariant. Terminal node of the coupled-oscillator diagram on the temporal lemniscate (VI.D27); receives the external zeitgeber via the dedicated photic input morphism and broadcasts phase to every peripheral clock through hormonal, autonomic, and thermal channels.

Primary registry anchor: VI.T17

Supporting items: VI.P09, VI.D27, VI.D25

1. I.K0 — Universe Postulate
2. VI.D15 — Life Sector
3. VI.D25 — Temporal Stability Predicate
4. VI.D27 — Temporal Lemniscate
5. VI.P09 — 24-Hour Cycle as τ¹ Rotation
6. VI.T17 — Circadian Rhythm as Poincaré Orbit — instantiated organism-wide via the SCN master pacemaker

Biomarker: SCN: ~20,000 paired neurons in the anterior hypothalamus above the optic chiasm; ipRGC photic input via melanopsin; output via cortisol pulses, melatonin (pineal), autonomic innervation, body-temperature rhythm; tissue-specific phase offsets in liver, skin, immune-cell clocks.

Measurable range: SCN free-running period in humans ~24.2h; entrainable phase-shift range ~±1h/day; full re-entrainment after transmeridian flight ~7–10 days (SCN ~1–2 days, liver ~5 days, lagging peripheral); shift-work disruption classified WHO Group 2A probable carcinogen.

Observation method: fMRI/PET of SCN activity, salivary dim-light melatonin onset (DLMO), continuous core-body-temperature minimum, single-cell luciferase reporters on PER2, SCN-lesion experiments in rodents, in vivo electrophysiology of SCN firing.

Calibration anchor: LG-Y02-kinetic-pseudoscalar-channel

Anchor chain:

1. VI.L18 chirality channel
2. stereospecificity of melanopsin's 11-cis retinal photoreceptor
3. homochirality of melatonin (D-tryptophan-derived in pineal cascade)

Manuscript reference: manuscript-sources/book-06/part02/ch15-circadian-rhythms.tex

Status: Planned

Related glossary entries

• LG-T01-circadian-rhythm Circadian Rhythm
• LG-T03-sleep-cycle Sleep Cycle (NREM/REM)
• LG-Y02-kinetic-pseudoscalar-channel Kinetic Pseudoscalar Channel