REM sleep follows the slow ("slow-wave sleep" denoting stages 3 and 4), and is the fifth and final stage of a sleep cycle which comprises 3 to 5 cycles of successive duration of each 70 to 90 min. This is the sleep phase during which the dreams that you remember happening (Born, 2006).
It is characterized by rapid eye movements, hence the English name of this stage of REM sleep to rapid eye movement, muscle atonia, increased breathing and irregular heartbeat, body temperature is in turmoil. There is a dilation of the pelvic organs and an erection that can be followed by ejaculation. The electrical activity of the brain is similar to that of wakefulness, as shown by the EEG (Born, 2006).
In a normal person, the duration of REM sleep occupies about 25% of the duration of a cycle, and increases with each cycle until waking. It is observed not only in humans but also in the majority of placental mammals and birds), activation is measured by placing electrodes on the bridge, the geniculate body and visual cortex (sometimes called cortex occipital, hence the name of PGO waves).
Question 2:
The dream of babies, especially in the first few months, typically is full of interruptions because their sleep cycles are shorter than those of adults. Adults are about six hours of sleep and two hours of light sleep (REM), usually in an uninterrupted night time. When we are in a cycle of light sleep, we wake up momentarily, but, unlike babies, we know how to get back to sleep. Babies have twice as many cycles of light sleep than adults, more light sleep than deep sleep and total sleep cycles are shorter what does this mean for families? Often interrupted sleep for everyone. Babies have a good chance of waking up frequently as they pass from deep sleep to light sleep in each sleep cycle. In the early months, babies need help falling asleep and falling back to sleep after waking. And often, you'll have to spend much time helping the baby to sleep in a deep enough for you to bed. All new parents have had the frustrating experience of gently rocking the baby or hold him until he falls asleep, bedtime and then at the moment when the head hits the mattress, see how he wakes up. What was the problem? The baby was still in the cycle of light sleep when he slept.
In these early days of baby's life, Dr. William Sears recommends in The Baby Book (The baby book), wait until the baby is deep asleep before bedtime. A sure sign of deep sleep and lasting are the arms and legs relaxed. Gently lift an arm or leg, and if you fall and your baby moves or wakes with a start, it means you are asleep. Lull, get out of the room walking on tiptoe, and sighs with relief (Hobson, ...