The body has a built-in time-keeping system that drives our daily rythms, particulary those of eating and sleeping. At the core of this is the daily chemical conversion of the wakeful hormone serotonin into the sleep hormone melatonin, a process that takes about 24h.
The daily cycle
Many hormones go through rhythmic fluctuations every day. These oscillations happen independently of any external prompting. Even in a black room eith no windows, the body gets a serotonin surge in the morning, which wakes it up. However, the rythms are not hard wired, they are constantly readjusted and can be changed radically when we travel to a different time zone.
The circadian clock
Our bodies run on a 24h hormone cycle, known as circadian rhythm. The biological processes that govern it are called the circadian clock, which is what governs all the body's rythms. One of the main cogs in this clock is a very small region of the brain known as a suprachiasmatic nuclus (SCN). Located very near the optic nerves, the SCN uses the amount of light entering the eye to calibrate the circadian clock
Can stress make you ill?
Stress hormones prepare us for fight or flight, but they also take a toll on some of our other system, particulary our immune system. Chronic stress can therefore lead to disease