Non REM sleep

Physiology

• Non-rapid eye movement sleep also known as quiescent sleep
• It is collectively sleep stages 1–3
• Unlike REM sleep, there is usually little or no eye movement during these stages.
• Dreaming occurs during both sleep states
• Muscles are not paralyzed as in REM sleep.
• People who do not go through the sleeping stages properly get stuck in NREM sleep, and because muscles are not paralyzed a person may be able to sleepwalk.
• Mental activities of NREM sleep are thought-like, whereas REM sleep includes hallucinatory and bizarre content.
• NREM sleep is characteristic of dreamer-initiated friendliness, compared to REM sleep where it's more aggressive, implying that NREM is in charge of simulating friendly interactions.
• The mental activity that occurs in NREM and REM sleep is a result of two different mind generators, which also explains the difference in mental activity.
• There is a parasympathetic dominance during NREM.
• Differences between REM and NREM activity are believed to arise from differences in the memory stages that occur during the two types of sleep.

Stages

1. Stage 1 occurs mostly in the beginning of sleep, with slow eye movement. Alpha waves disappear and the theta wave appears. People aroused from this stage often believe that they have been fully awake. During the transition into stage-1 sleep, it is common to experience hypnic jerks.
2. Stage 2: No eye movement occurs, and dreaming is very rare. The sleeper is quite easily awakened
3. Stage 3 is deep sleep, slow-wave sleep (SWS).
   • Delta waves, associated with "deep sleep", began to occur.
   • Dreaming is more common in this stage, though not as common as in REM sleep.
   • Dreams content is disconnected, less vivid, and less memorable than those of REM sleep.
   • This is also the stage during which parasomnias most commonly occur.

Charactristics

• Sleep spindles are unique to NREM sleep. The most spindle activity occurs at the beginning and the end of NREM. Sleep spindles involve activation in the brain in the areas of the thalamus, anterior cingulate and insular cortices, and the superior temporal gyri.
• Muscle movements: The tonic drive to most respiratory muscles of the upper airway is inhibited.

This has two consequences:

1. The upper airway becomes more floppy.
2. The rhythmic innervation results in weaker muscle contractions because the intracellular calcium levels are lowered, as the removal of tonic innervation hyperpolarizes motoneurons, and consequently, muscle cells.

However, because the diaphragm is largely driven by the autonomous system, it is relatively spared of non-REM inhibition. As such, the suction pressures it generates stay the same. This narrows the upper airway during sleep, increasing resistance and making airflow through the upper airway turbulent and noisy. For example, one way to determine whether a person is sleeping is to listen to their breathing - once the person falls asleep, their breathing becomes noticeably louder. Not surprisingly, the increased tendency of the upper airway to collapse during breathing in sleep can lead to snoring, a vibration of the tissues in the upper airway. This problem is exacerbated in overweight people when sleeping on the back, as extra fat tissue may weigh down on the airway, closing it. This can lead to sleep apnea.^{[citation needed]}