Jet lag is a physiological condition caused by an an alteration to the body is biological
clock caused by rapid trans-meridian travel on a jet aircraft Our biological clock , known as the circadian rhythm is controlled by a tiny part of the brain called the hypothalamus , which activated various body functions such as hunger , thirst and sleep during a 24 hour cycle It also regulated body temperature , blood pressure and the level a hormones and glucose in the bloodstream When you travel across several time zone , the body clock will not correspond with the destination time, so it experiences daylight and drakness in conflict with its previously established rhythm For exemple, if you travel from thailand to U.S. where ( on the East Coast of the US ) there is a 12 hour time difference, your body previously set to Thailand time, will think that it is still 11 AM, though the local time in the U.S. is 11 PM Consequently, you may find it impossible to fall asleep at night However , crossing one or two time zones ( such as traveling from Thailand to Japan ) typically does not cause jet