Since today is the longest day of the year, it seems appropriate to discuss circadian rhythm and the role that daylight plays in our sleep cycle. 

Your circadian rhythm is an ingrained biological clock that regulates the timing periods of tiredness and wakefulness throughout the day. Your body clock is calibrated by the appearance and disappearance of natural light in a 24-hour period. The term circadian is derived from the Latin “circa diem” meaning “approximately a day.”

The functions of your circadian rhythm are based in the part of the brain known as the hypothalamus. Within the hypothalamus are a group of cells known as the suprachiasmatic nucleus (SCN), which is connected to our optic nerves that sense changes in light. The SCN is also responsible for regulating many body functions that revolve around the 24-hour cycle including: body temperature, heart rate, blood pressure, and the release of hormones such as melatonin which helps us with sleep.

How Your Body Clock Works