1.   For decades, researchers felt that the same or similar receptors were responsible for collecting light and sending signals to the master clock, called the suprachiasmatic nucleus.

2.   In mammals, the master clock is in the suprachiasmatic nucleus of the brain, just above where the optic nerves from each eye cross over.

3.   It was not a problem in the master clock, Koskinen said.

4.   Moreover, hemoglobin carries nitric oxide, a neurotransmitter that could carry information about day length to the master clock in the brain.

5.   Signals travel from the master clock to the pineal gland and other centers that release hormones throughout the body.

6.   Some creatures have light sensitive cells on various parts of their bodies that help regulate the master clock.

7.   The glitch, which was corrected, affected only the Web site, not the master clock.

8.   When activated, they send impulses to the master clock, which sets biological rhythms.