Sleep

SLEEP

Sleep is a state where in the body is in a hibernating state. keeping every aspect of your mind and body in check, its the bodies own way of doing maintenance, ancient people used to think that sleep is where the soul leaves the body to rejuvenate its self, some ancients think that sleep is where god and man  connects, while some say sleep where the soul lingers with the next world.

well, much of sleep is still unknown even with todays technology.

science have yet to discover the full extent of sleep, but we do know now that sleep is divided into  2  classes of sleep. 

• REM
• NREM

• REM or Rapid eye movement  is the shallow part of the sleeping cycle, where the brain is active , the brain glows 100% in this stage as shown in the MRI , which means this is the stage where the mind sorts out everything that it has learned and storing informations in the right place, from eating experience to school and spots activity. so even when we sleep the mind is still practicing and processing the details. Sleep proceeds in cycles of REM and NREM,  the order normally being N1 → N2 → N3 → N2 → REM. There is a greater amount of deep sleep (stage N3) earlier in the sleep cycle, while the proportion of REM sleep increases later in the sleep cycle and just before natural awakening.
•  in 1937  Alfred Lee Loomis and his coworkers, separated the different electroencephalography (EEG) features of sleep into five levels (A to E), which represented the spectrum from wakefulness to deep sleep. In 1953, REM sleep was discovered as distinct, and thus William Dement and Nathaniel Kleitman reclassified sleep into four NREM stages and REM. The staging criteria were standardized in 1968 by Allan Rechtschaffen and Anthony Kales in the "R&K sleep scoring manual." In the R&K standard, NREM sleep was divided into four stages, with slow-wave sleep comprising stages 3 and 4. In stage 3, delta waves made up less than 50% of the total wave patterns, while they made up more than 50% in stage 4. Furthermore, REM sleep was sometimes referred to as stage 5.                                                                                                                   the AASM in 2004 commissioned the AASM Visual Scoring Task Force to review the R&K scoring system. The review resulted in several changes, the most significant being the combination of stages 3 and 4 into Stage N3. The revised scoring was published in 2007 as The AASM Manual for the Scoring of Sleep and Associated Events. Arousals and respiratory, cardiac, and movement events were also added.

Sleep stages and other characteristics of sleep are commonly assessed by                        polysomnography in a specialized sleep laboratory. Measurements taken include EEG of brain waves, electrooculography (EOG) of eye movements, and electromyography (EMG) of skeletal muscle activity. In humans, each sleep cycle lasts from 90 to 110 minutes on average, and each stage may have a distinct physiological function. This can result in sleep that exhibits loss of consciousness but does not fulfill its physiological functions (i.e., one may still feel tired after apparently sufficient sleep).

Scientific studies on sleep having shown that sleep stage at awakening is an important factor in amplifying sleep inertia. Alarm clocks involving sleep stage monitoringappeared on the market in 2005. Using sensing technologies such as EEG electrodes or accelerometers, these alarm clocks are supposed to wake people only from light sleep.

• NREM or Non Rapid eye movement is the most refreshing sleep compared to REM, little dreaming is present in the NREM which means no rapid eye movement which is rather tiring on both eyes making your sleep unsatisfied. 
• Stage N1 refers to the transition of the brain from alpha waves having a frequency of 8–13 Hz (common in the awake state) to theta waves having a frequency of 4–7 Hz. This stage is sometimes referred to as somnolence or drowsy sleep. Sudden twitches and hypnic jerks, also known as positive myoclonus, may be associated with the onset of sleep during N1. Some people may also experience hypnagogic hallucinations during this stage, which can be troublesome to them. During N1, the subject loses somemuscle tone and most conscious awareness of the external environment.
  Stage N2 is characterized by sleep spindles ranging from 11–16 Hz (most commonly 12–14 Hz) and K-complexes. During this stage, muscular activity as measured by EMG decreases, and conscious awareness of the external environment disappears. This stage occupies 45–55% of total sleep in adults.
  Stage N3 (deep or slow-wave sleep) is characterized by the presence of a minimum of 20% delta waves ranging from 0.5–2 Hz and having a peak-to-peak amplitude >75 μV. (EEG standards define delta waves to be from 0–4 Hz, but sleep standards in both the original R&K, as well as the new 2007 AASM guidelines have a range of 0.5–2 Hz.) This is the stage in which parasomnias such as night terrors, nocturnal enuresis, sleepwalking, and somniloquy occur. Many illustrations and descriptions still show a stage N3 with 20–50% delta waves and a stage N4 with greater than 50% delta waves; these have been combined as stage N3.

  
  

  
  
  Dreams
  Brief History
  
  
  Dreams are interpreted back in the ancient times as a vision or a message from their god, while others defined dreams as a demonic in nature as of defined in berlin in 1868. in the bible alone, dreams are often mentioned as one gods medium of communication to connect with his people.
  
  
  Dreams are believed to be both  good and bad for dreams may lead them to their fortune or simply misdirect them into a pit of despair 
  
  
  Macrobious and Artemidorus Dreams are first believed to be  influenced by the present of the past and was unimportant in respect of the future.
  
  
  prophesies are also a big customer to dreams, where ancients believe that dreams is all that .
  
  
  Dreams Defined today
  
  
  Dream today is defined as a natural mind process where from  the deepest part of sleep 
  our mind returns to the REM where  some of our consciousness is retained.
  
  
  the human mind usually redirects, stores images and everything that has happened throughout the day and may even bring back some of the memories from the past, its just so.... when  our mind accidentaly goes back to the REM, some of our conciousness is stimulated which makes us interpret them as dreams.
  although most of the dreams cannot be remembered it doesn't mean that you didn't dream 
  at all. in fact we always dream when we sleep its just so that we cant remember anything when we wake up because we are not in the slightest.. conscious at that time. 
  
  
  Modern  theorists theorizes that dreams are present throughout the day even when we are awake. but that is still to be proven