The term circadian comes from the Latin phrase “circa diem,” which means “approximately a day.” Circadian rhythms work by helping to make sure that we can maintain a regular pattern across a 24-hour period. The term ‘circadian rhythm’ is not exactly the same thing as the term ‘body clock’. Internal biological clocks help regulate the timing of bodily processes. So, in other words a circadian rhythm is an effect of a biological clock rather than being an actual body clock.
Circadian rhythms are closely connected to the 24-hourcycle of night and day. The circadian rhythms throughout the body are connected to an internal clock located in the brain. It is found in the suprachiasmatic nucleus (SCN), which is in a part of the brain called the hypothalamus. The SCN is sensitive to light, and this is why light is so central to the regulation of our sleeping patterns. While other cues, like exercise, work patterns, social activity, and temperature, can affect the internal clock, light is the most powerful influence on circadian rhythms.
There are many times when the circadian system and the internal biological clocks can be out of synch and this can lead to sleeping difficulties and poor quality of life. Disruptions to circadian rhythm can occur due to behaviours such as travel and working non-standard hours. Health experts have identified a number of types of circadian rhythm sleep-wake disorders (CRSWD) based on their characteristics and causes.