Jet Lag Caused By Out-of-synch Brain

The droopy-eyed jet lag that comes after a long flight could be caused by two groups of cells at the base of the brain falling out of synch, a new study suggests.

The body has a built-in time-keeping system, known as a circadian rhythm, that helps us keep track of when it's time to eat, sleep, wake up and perform other body functions. This system is partly governed by the cycle of day and night.

Changing time zones or working the late shift can throw off the body's sense of timing because it changes the timing of our exposure to light.