Circadian rhythm

[Ref: WG22:p234-235]

• Almost all cells have rhythmic fluctuations in their functions that are about 24 hours in length.
• In the liver, the rhythm is influenced by pattern of food intake
• In almost all other cells, the rhythms are entrained by the paired suprachiasmatic nuclei (SCN)

Suprachiasmatic nuclei

• Above the optic chiasm
• One on either side
• Receive information about light-dark cycle
  * via the retinohypothalamic fibres
• 2 different peaks of circadian activities

NB:

• Retinohypothalamic fibres pass from optic chiasm to SCN