Falling asleep, we find ourselves in a mysterious world of the unknown. We see fascinating dreams, or simply enjoy our rest. While we are recovering from a tiring day, our body keeps functioning. But what happens during those hours when we’re unconscious?

The Brain

There are four different stages of sleep lasting from 70 to 120 minutes. The pattern consists of three non-REM stages and one REM (rapid eye movement) stage. Deep sleep happens during the REM and the last of the non-REM stages. In these phases the brain waves slow down, setting the right conditions for the process of body recovery. Sleep is basically the unconscious human version of car repair, the brain being our car mechanic and repairing the cells, the tissues, filling the body up with the petrol of lively energy. Another interesting thing to know is that the brain sends signals to turn off motor neurons in the spinal cord, causing it to temporarily paralyze to prevent movement during sleep. That’s why so often people feel like they’re falling in their dreams. 

The Eyes

Although your eyelids are closed, your eyes continue to move constantly during sleep. In the early stages of sleep, these are slow circular movements, and in the deep sleep stages they become much faster and more intense. The rapid eye movement sleep stage is called that way for a reason.

The Hormones

One of the reasons you get drowsy when it’s getting dark is melatonin, the so-called vampire hormone, which promotes sleep. While snoozing, its concentration gradually decreases into the morning hours, and other hormones come into play. In fact, a variety of hormones vary across the 24-hour day and are highly regulated by the circadian and sleep-wake cycles. These include two hormones you probably haven’t heard of, but felt the effect of.

Leptin and ghrelin are the duo responsible for your sense of hunger. A lack of sleep has been proved to cause increased levels of ghrelin and decreased levels of leptin, which leads to increased hunger and appetite. Inadequate sleep simply amplifies ghrelin’s “I’m hungry” signal to the brain while muting or completely removing leptin’s “I’m full” signal. So next time you wake up short of sleep, don’t be surprised you feel like eating an elephant.

The Body Temperature

Throughout all stages of sleep, the body temperature gradually drops due to its own circadian rhythm. Changes in hormone concentration are responsible for this as well. Low body temperature promotes sound sleep and recovery, so opening the windows in your bedroom an hour before going to bed is a must.

The Muscles

Despite the fact that we often roll over during sleep, the muscles remain relaxed throughout the night. In fact, because the muscles are relaxed, your brain may confuse relaxation with weakness. And sometimes this confusion is what makes you feel like you’re falling in your dreams.

The Digestive System

Since the amount of energy required by the body is significantly reduced at night, the digestive system also slows down (and we already know which hormone is responsible for that). If you stuff yourself with food before bed, your body may have to work all night to digest the snacks. Don’t eat 3-4 hours before bedtime, and your body will be forever thankful.