According to Science Daily the body may have more than one clock:
Our latest research suggests that a separate but likely related clock resides in the adrenal gland. The adrenal gland is involved in several important body functions, such as body temperature regulation, metabolism, mood, stress response and reproduction. The research also suggests that other peripheral clocks reside throughout the body and that these clocks are perhaps interconnected.”
(One version of the paper can be found here)
Specifically, researchers measured gene expression in the adrenal gland of monkeys during a 24-hour period (six times a day, four-hour intervals). In analyzing this information, researchers identified 322 genes in the adrenal gland with functions that varied rhythmically over a 24-hour period, meaning that each gene’s function peaked and diminished at the same time each day. Interestingly, the scientists also noted that a subgroup of these 322 genes also exist in the SCN — the home of the body’s master body clock. This suggests that the adrenal gland has its own timing mechanism that is related to, but separate from, the SCN body clock.
Filed under: Biology