Suprachiasmatic nucleus

Relay nuclei · detail

Hypothalamic nucleus lying directly above the chiasm. Melanopsin-containing intrinsically photosensitive ganglion cells send the retinohypothalamic tract to it from the chiasm, entraining the circadian clock independently of rods and cones.

Traced from the start

  1. Temporal hemiretinaNasal hemiretinaMacula and papillomacular bundle
  2. Optic nerve (CN II)
  3. Optic chiasm
  4. Suprachiasmatic nucleus

Detail

Afferent
Retinohypothalamic tract from melanopsin ganglion cells (about 1% of ganglion cells)
Output
Paraventricular nucleus, then sympathetic chain to the pineal for melatonin
Function
Entrains the circadian rhythm to the light-dark cycle

When it goes wrong

Loss of rods and cones with surviving ganglion cells

Circadian entrainment and a slow pupillary response can persist despite blindness

Practise this structure

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