Chapter 9

 The circadian cycle is our inner biological clock.  It governs how we work every day as a calibrated machine. Activities as a wake-up, feel hungry, secrete hormones, and also the time that we usually go to sleep are regulated by this intern mechanism that keeps us working at the same pace as long as possible for our own sake. In summary, it rules our individual internal and external routines.  Without this neurological regulation, we would be lost during the hours of the day and start to display irregular behaviors that will have no time to happen because we would be totally maladapted to function in a day of 24 hs as we know. 

People's circadian cycle was affected over time. Their life activities were influenced by the light of the sun. Our ancestors had more time to sleep. There was no way for someone to become a workaholic; therefore, they were not so busy during the whole day, and they could sleep more, rest, take a nap and feel better at the end of the day for sure. Their circadian cycle worked differently from what we experience nowadays.  Maybe the habit of having a siesta in Spain still persists in some cultures because their ancestors reserved that time of their day to rest and refresh their minds, revealing that these cycles are differents and attend to personal demands.  

On the other hand, Chinese people, for example, have been working more and more hours across the years, gradually decreasing their time of sleeping over time.  Such a tendency of sleeping less certainly brings consequences in the long term.  Our biological clock is extremely functional to keep us healthy and alert if we are not asleep. It is this mechanism that makes us run our lives in a normal constancy during our lifetime. 

The rise of the fire and the lamp or any artificial light has impacted human's biorhythm in many ways but in a gradual and adaptative form along the centuries.  Thence, a drastic change of habits will naturally dysregulate our internal clock, desynchronizing our timing to certain things and provoking changes in internal mechanisms that control the chemical activities that control people's psychologic and physiologic activities. The consequences can vary in an array of problems in sleep, digestion, alertness, mood, and weight control.  Such problems are usually related to some professions requiring big changes in individuals' lifestyle habits that may develop these symptoms when they start to work in alternate shifts that prevent them from preserving their own circadian cycles.