four stages of sleep
Body also saves energy, restores tissue and gains muscle mass.
Whenever a person wakes up at night, he returns to the initial stage.
Sleep has four phases, and each one is responsible for a different activity - either the release of hormones, or the consolidation of memory and learning.
For this reason, sleep well and continuously is important, since whenever a person wakes up at night, they return to the initial stage of sleep. And this may interfere with some processes that only occur at the deepest stage: REM.
Individuals who make a lot of mental effort, such as college entrance exams, have a stronger REM sleep.
Early in the morning, the body stops releasing growth hormone (GH) and begins to produce the hormone cortisol, which controls inflammation, allergies, stress, and helps maintain emotional stability, according to sleep medicine specialist Sérgio Tufik and Marco Túlio de Mello, professor of sleep medicine and biology at the Sleep Institute of the Federal University of São Paulo (Unifesp).
Other hormones released are melatonin, adrenaline, TSH (which stimulates the thyroid and has a peak in early onset) and noradrenaline (which favors REM sleep).
According to Tufik, people only remember the dream when they wake up dreaming - so in dreams studies, they are awakened in the REM phase. A normal individual dreams four to five times a night.
Source: http://g1.globo.com/bemestar/noticia/2011/12/sono-tem-quatro-fases-que-liberam-hormonios-e-consolidam-memoria.html
