The human stages of sleep are fully dependent on the presence of light or the absence of it (darkness). Although it seems very simple (we sleep at night and we wake up in the morning when the sun comes out), there is a very complex explanation behind it.
When light is detected, a nervous stimulus is sent from our retina to our hypothalamus, from where many different functions will be started (raising body temperature, regulating the secretion of hormones etc). The importance of melatonin in our sleep is such, that one of the most important functions commanded by the hypothalamus is delaying the secretion of melatonin, until the next sleeping cycle is to begin.
What is melatonin?
Melatonin is a hormone produced in our pineal gland that is introduced in our circulatory system every day approximately at 9 pm. It helps our body enter a relaxed state, which makes the process of falling asleep much easier.
This (Pineal gland) is a pea-sized gland located just above the middle of the brain. During the day the pineal is inactive. When the sun goes down and darkness occurs, the pineal is “turned on” by the SCN and begins to actively produce melatonin, which is released into the blood.National Sleep Foundation
What are the problems related?
It’s important to keep in mind that the adequate proportion of melatonin in our body will ensure a prosperous sleeping experience, given the absence of any conditions that would otherwise affect it.
However, there are many threats which will most likely affect our production of melatonin. One of the most prominent hazards is blue light, especially the blue light we are exposed to after the “darkness period” has started.
This is because our body gets confused as it should be producing higher levels of melatonin but the blue light coming from our phones, laptops or tablets won’t allow it.
In the long run, consistent exposure to blue light at late hours will affect our sleeping cycles causing sleeping disturbances.
Blue light does not only come from our digital devices, but fromthe sun as well. In fact, sunlight is the biggest source of blue light we are exposed to.
This means that any influence from sunlight while we sleep can also affect the secretion of melatonin. For instance, sleeping with our blinds opened will affect the late stages of our sleep and can make us wake up earlier than when they are closed.