Читать книгу Sleep: The secret to sleeping well and waking refreshed - Prof. Idzikowski Chris - Страница 32

Stage 5 sleep is commonly known as Rapid Eye Movement, or REM sleep, named after the darting eye movements that have been observed in people in this sleep stage. It appears after 80-90 minutes’ sleep in recurring phases known as an REM cycle. It initially lasts for about ten minutes, then increases in length, with the final one lasting for about an hour. In young adults, REM sleep can last for up to two hours in total.

For many sleep scientists, REM sleep is the most interesting and exciting of all sleep stages, for this is when dreaming occurs, and is when the brain is most active. In fact, curiously, EEGs taken at this time are more similar to those taken during wakefulness than at other sleep stages. The brain shows increased cerebral metabolism, cerebral blood flow, intracranial pressure and brain temperature, and many parts of the brain that control functions such as heart rate, blood pressure, breathing, body and brain temperature and sweating are less well regulated than at other times. Even sexual organs are aroused and men often have penile erections. In fact, there was a time when REM EEGs were used to determine whether men’s impotence was physical or psychological, though this has all changed in recent years with the introduction of Viagra.