In the case of our sleep and awake circadian rhythm, it makes us have the strongest desire to sleep between the midnight hours and sunrise, and also a strong desire to sleep in the middle of the afternoon, jut at the time of the “siesta” (afternoon nap).
In our brain, the neurons that generate this biological clock are located within the hypothalamus, which also happens to regulate our appetite among other biological states. These brain cells are found just below the optical nerves which take the information from what we see to the brain’s visual centers, explaining the influence that light has on our internal clocks.
Our internal clocks are mostly self regulating, however there are external factors that keep them working on a daily basis. These factors are primarily daylight; time cues, and melatonin.
Why these three? Let’s analyze each one of them:
Light: this is the most influential factor that affects our biological clocks, this is because our eyes are connected to the specific neuron cells in charge of this internal clock. Many of us have experienced how in a brief time (one or two days) we can adapt our schedule to a new time zone, which varies according to the actual time difference and our body’s incorporation of this change, when we travel to it. It is how we experience Jet lag.
Time cues: We all read our watches, clocks, we follow schedules for work, commuting and social events. These affect our internal clock.
Melatonin is a hormone produced by the pineal gland in our brain. It is produced in a daily pattern, closely related to light: melatonin levels increase when late nighttime is approaching and decrease just after sunrise. Melatonin’s production can be controlled and modified by exposure to light. Our braincells that manage our circadian clock have receptors for this hormone, that is why it is believed to be an important factor for keeping it on track.
Melatonin is commonly used to help with jet lag when one travels, you might have tried it!