Main characteristics of N-REM: low muscle tonus and variability of cortical activity evidenced by EEG: K complex and slow waves. The slow waves decrease with age. N-Rem is synchronic (all activities might happen at the same time. Main characteristics of REM: is desynchronized, muscles are atonic and dreaming is typical.
Delta waves are associated with the deep sleep stages, stage 3 and REM. During stage 3, less than half of brain waves consist of delta waves, while more than half of brain activity consists of delta waves during REM sleep. Sleep spindles—bursts of 11–15 Hz (sigma frequency band) activity, typically between 0.5 and 2 s in duration—are characteristic transient features of the sleep electroencephalogram (EEG). Spindles are most prominent during N2 sleep and are in fact a defining feature of this stage. The K-complex is a waveform seen on electroencephalography during the second stage (N2) of NREM sleep.] IN SUMMARY; N-REM stage 2 has spindles and K complexes (remember bruxism occurs moslty here), and Delta waves mostly in deep sleep (stage 3) and REM.
A Way to remember: Think of N-REM as the organized brother, with structure (stages), go to rest first, and has highest scores at school (most of the night belongs to N-REM. REM is the terrible and dreamer brother, will have many interruptions and appears several times during the night (4-6 times), moving a lot. As he ages, he quiets down. In some pictures (sleep studies), REM uses a bold hat, and you can recognize him! (sleep studies might have a stronger or different color for REM episodes), he can be sitting in the floor or over a chair in the upper part of the “picture”. As N-REM ages, he is more selective, and prefers to reduce his options to 1 or 2 (so stages 3 and 4 are diminished). N-REM is sad to loose his stage 3, which he calls Special. In reality is a Slow Wave (SWS), and occupies the deepest part of his heart (SWS is stage 3 is deep sleep, occurs 20% of the night, but it does decrease with age). N-REM has a female cousin, and for some reason, she kept her choices, and did not let the Special stage (SWS or stage 3) go away (SWS is also delta sleep). End of the history to remember general characteristics of N-REM (organized brother with a Special stage) and REM, the dreamer.
REM is accompanied by contraction of the middle ear muscles, producing a protective to loud noise. REM sleep is mediated by brainstem, so damage in that area (or a tumor) might produce changes in sleep pattern. Narcolepsy is related with changes in REM sleep, secondary to changes in a specific type of neurons located in hypothalamus (hypocretin). Cerebral glucose, oxygen metabolism, and cerebral blood flow decreases in NREM, specially in stages 3 and 4.
Changes on sleep patter with aging are not always normal. It could be related with systemic conditions, so never think that is "normal" to have a daytime napping or all night wake up older adult. Excessive daytime Sleepiness (EDS) might be a consequence of not enough sleep time, problems with sleep architecture (fragmented sleep), and even a symptom of severe systemic conditions (narcolepsy or neurological diseases). EDS is a problem with functionality and performance, and needs to be addressed.
Sleep deprivation affect performance, vigilant attention, and increases mortality risk (neuroendocrine and immune systems are directly affected). Sleep deprivation changes brain metabolism. Sleep cycles are related with same brain structures of cognitive and emotional behavior, so altered sleep impairs behavior from a physiological point of view. Sleep produces autonomic changes. In Sleep disorders, it is possible to have non-functional autonomic regulatory areas, so the CV system is jeopardized. Nighttime monitoring of cardiorespiratory function is of great diagnostic value, considering the possible co-existence of CV disease and sleep apnea.
Some substances and their effect: Different effects from serotonin: Serotonin release produces arousal (higher level in waking), but also might facilitate N-REM sleep. Norepi is more present in N-REM. Histamine is sedative.
To remember: chemoreflexes mediate response to hypoxia and hypercapnia plus CV effects. The most important peripheral arterial chemoreceptor is in the carotid bodies, and respond primarily to changes in the partial pressure of oxygen, with an increase in respiratory muscle output, hyperventilation and vasoconstriction. The central chemoreceptors are in the brainstem and respond to changes in pH (carbon dioxide), and will elicit sympathetic and respiratory activation.
Hypoglossal, trigeminal and facial nuclei innervate muscles important to upper airway patency. The pre-Bötzinger complex (preBötC) is a cluster of interneurons in the ventral respiratory group of the medulla of the brainstem. This complex has been proven to be essential for the generation of the respiratory rhythm in mammals, and has opioid receptors (which in part explains why there is a respiratory depression with opiods).
Some concepts:
Meir Kryger, Thomas Roth and William C. Dement. Principles and Practice of Sleep Medicine. Sixth Edition • 2017
Xie A. (2012). Effect of sleep on breathing - Why recurrent apneas are only seen during sleep. Journal of thoracic disease, 4(2), 194–197. https://doi.org/10.3978/j.issn.2072-1439.2011.04.04
https://quizlet.com/10052033/psychology-sac-1-sleep-general-flash-cards/
https://www.youtube.com/watch?v=rMHus-0wFSo