SCN (Suprachiasmatic nucleus)

Suprachiasmatic nucleus: a collection of several thousand nerve cells situated above (supra) the intersection of visual nerves (chiasma). Now considered as the main regulator of the internal clock. Each of the nerve cells in the SCN has its own internal clock. Normally the internal clocks of these cells are in synchronism and therefore amplify the zeitgeber signal to a common strong control signal for the internal clock.