bio

Suprachiasmatic nucleus

A cluster of some twenty thousand neurons in the hypothalamus, sitting just above where the two optic nerves cross - and the master clock of mammals. Nearly every cell in the body carries a clock of its own, but they would drift apart without a conductor; the suprachiasmatic nucleus keeps that whole population of peripheral clocks running in step with one another and with the outside world. It receives light through a dedicated line running straight from the retina, entirely separate from the image-forming system - it does not see, it only meters light.