Most of us have come across the fact that we have a ‘body’ or ‘biological’ clock – we actually have several – our biological clocks are groups of interacting molecules in cells throughout the body, however we have a ‘master-clock’ – a group of nerve cells – situated in the brain (the suprachiasmatic nucleus, or SCN) which is located in the hypothalamus, an area just above where the optic nerves cross. This consists of around 20,000 nerve cells and co-ordinates all the bodies clocks so that they are all working in sync. These biological clocks drive our circadian rhythms.
Circadian rhythms – put simply – are physical, mental and behavioural changes that follow a roughly 24-hour cycle, responding primarily to light and darkness (with our ‘body-clock’ at the steering wheel) in our environment. They are found in most living things, including animals, plants and many tiny microbes. We also have genes that direct these circadian rhythms. The study of circadian rhythms is called Chronobiology.