How Biological Clocks Work
Anyone who has traveled has experienced jet lag—that groggy realization that while your day is beginning in Washington, D.C., the night you just left in San Francisco is hardly over.
Jet lag is an inconvenient reminder that the body is set to a 24-hour clock, known by scientists as circadian rhythms, from the Latin circa dies, “about one day.” An internal biological clock is fundamental to all living organisms, influencing hormones that play a role in sleep and wakefulness, metabolic rate, and body temperature.
Disruption of circadian rhythms not only affects sleep patterns but also has been found to precipitate mania in people with bipolar disorder (manic-depressive illness). Other types of illnesses also are affected by circadian rhythms; for example, heart attacks occur more frequently in the morning while asthma attacks occur more often at night.
Although biological clocks have been the focus of intensive research over the past four decades, only recently have the tools needed to examine the molecular basis of circadian rhythms become available. Early studies pointed to an area of the brain, the hypothalamus, as the location of the circadian pacemaker in mammals. More findings here.