Throw out all your clocks and your body still has a rough idea of the time of day. That’s because it has it’s own clock – the body clock. It tells the cells in your body what time of day it is and so controls a whole bunch of different processes that need to be carefully timed and coordinated in order for your body to work properly.
Keeping your cells in sync creates a certain rhythm to what they do all day and night – a circadian rhythm. And it isn’t just us that have it but plants and animals too.
Circadian rhythms roughly follow a 24-hour cycle, so we feel sleepy at night and awake in the morning. It also affects our eating habits, digestion, body temperature and alertness. How? By controlling hormone production.
So how does your circadian rhythm get its rhythm? From the tick tock of your body clock. Or rather body clocks, as we have lots – an all-powerful master clock in the brain and other little clocks in different tissues and organs. The little clocks get their timing from the master clock and the master clock gets its timing from sunlight. Sunlight stimulates cells in your eyes that send signals to the brain, which uses this information to figure out the time of day and set the master clock.
Interestingly, if you were kept in complete darkness for days, your circadian rhythm would persist. But mess with light and it gets confused. Being exposed to bright light at night when your body should be winding down – say staring into a laptop screen – confuses your body clock. This changes your circadian rhythm, which messes around with your hormones. The end result: poor sleep and with night workers a greater chance of developing certain diseases.