Our sleep is regulated by two processes together:
♦ sleep homeostat, which controls the impulse to sleep;
♦ circadian (daily) timer that controls sleep time.
Homeostat sleep: the word “homeostat” is derived from the Greek words “homeo” – “permanent”, and “stasis” – “stable”. They are described with a complex sequence of processes occurring in the body that support our bodies (as you have already guessed) in a state of constancy and stability. The sleep homeostat determines the required duration depending on the actual duration and degree of perceptible fatigue. For example, if you rest in just a couple of hours, the homeostat will cause lethargy, reminding you to immediately go to bed – so that everything is balanced and the body works like a clock.
Think of it as an internal debt collector or a regulator: you owe your body several hours of sleep, and the homeostat must make sure that you paid. Circadian timer: a fun name for a biological clock. Our body is programmed to respond to light and darkness throughout the entire daily cycle. For each person, biological clocks work in slightly different ways – maybe you are one of those who feel themselves on the rise in the morning, while others thrive in the afternoon or evening.
All of this is controlled by the “sleep hormone” – melatonin. In the dark, the brain sends a command of the pineal gland to secrete melanin, as a result of which you experience fatigue, while less time melatonin is released during daylight hours, so you feel invigorated.
That is why people who work in shifts and those who are in a long winter (for example, residents of Scandinavian countries) may suffer from seasonal affective disorder (ATS).
Their bodies produce more melatonin than usual, or more than the ideal amount (given the need for intensive work), which leads to permanent fatigue or emotional decline. In this, combined with the cold, lies the reason that many people in the winter months feel a desire to lie down in “hibernation.”
In debt to bed
To think that you owe sleep is a simple way of thinking about what happens when you lose sleep. The more you have to (for example, if you haven’t been sleeping for a long time), the more tired you feel. Fortunately, the sleep homeostat (debt collector) does not require you to immediately recover all missed hours of sleep. You can return the debt in the next night, in a couple of weeks or even in the next few months. Therefore, do not panic if from time to time you spend a sleepless night or a couple of such nights. Studies show that just two hours of sleep is enough to prevent the harmful effects of insomnia on brain activity. You will not be in the best shape, but you will do fine, so remember: if you occasionally sleep less than usual – this is fixable, the problem arises when sleepless nights happen often.
Another good news: in order to feel better, you need to make up just a third of the time spent without sleep. For example, for good health, Luce needs to sleep six hours a day, but for the last two days she managed to sleep only three hours each, which means she needs to fill only two of the six lost hours (one third of her debt); and the period in which she must replenish these hours is unlimited.
The body compensates for the lost and restores the balance between the actual sleep time and your need for it.