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Activity and alertness is reduced during sleep. While sleep affects the entire body, it most strongly affects the nervous system. Many important bodily functions, like waste cleanup and memory processing are supported by sleep. There are two kinds of sleep: rapid eye movement (REM) sleep and non-REM sleep. Non-REM Sleep has stages, which start at light sleep and progressively get deeper. In REM sleep, the eyes move quickly | Activity and alertness is reduced during sleep. While sleep affects the entire body, it most strongly affects the nervous system. Many important bodily functions, like waste cleanup and memory processing are supported by sleep. There are two kinds of sleep: rapid eye movement (REM) sleep and non-REM sleep. Non-REM Sleep has stages, which start at light sleep and progressively get deeper. In REM sleep, the eyes move quickly, notably, most dreams occur in it. NREM sleep stages are numbered from 1 to 3, from lighter to deeper. REM and Non-REM sleep alternates, repeating in cycles of around 90 minutes. | ||
== Measurement == | == Measurement == | ||
[[File:EEG Brainwaves.svg|thumb|upright|The differently named frequency bands of neural oscillations, or brainwaves: delta, theta, alpha, beta, and gamma.]] | |||
Sleep originates in the brain. The brain communicates within itself using electrical signals, they can be measured using electroencephalography (EEG), where electrodes are attached to the scalp and the resulting signals are measured. Additionally, eye movement is an indicator of sleep, we can measure the electrical signals causing eye movements using electrooculography (EOG), which involves attaching electrodes around the eye. Finally, skeletal muscle movement can also be used to measure sleep, and by attaching electrodes to skeletal muscle, its activation can be measured as an electrical signal, this is called electromyography (EMG). Other tests are also performed, however, these three are most useful to distinguish sleep stages. Together, these methods are called polysomnography (PSG). | Sleep originates in the brain. The brain communicates within itself using electrical signals, they can be measured using electroencephalography (EEG), where electrodes are attached to the scalp and the resulting signals are measured. Additionally, eye movement is an indicator of sleep, we can measure the electrical signals causing eye movements using electrooculography (EOG), which involves attaching electrodes around the eye. Finally, skeletal muscle movement can also be used to measure sleep, and by attaching electrodes to skeletal muscle, its activation can be measured as an electrical signal, this is called electromyography (EMG). Other tests are also performed, however, these three are most useful to distinguish sleep stages. Together, these methods are called polysomnography (PSG). | ||
=== | === Brainwaves === | ||
[[ | Brainwaves, or neural oscillations, are repeating patterns visible in EEG. Normally, EEGs show activity in frequencies ranging between 1 and 30 [[Wikipedia:Hertz|Hz]] and 20 to 100 [[Wikipedia:Volt|μV]]. There are different named categories of neural oscillations characterized by [[Wikipedia:Frequency|frequency]]. When awake and alert, an EEG shows high-frequency, low-voltage oscillations, while alpha waves are produced during relaxation. | ||
{| class="wikitable" style="margin:auto" | |||
|+ Oscillation types | |||
! Name | |||
! Frequency range | |||
|- | |||
| Delta | |||
| 0.5-4 Hz | |||
|- | |||
| Theta | |||
| 4-7 Hz | |||
|- | |||
| Alpha | |||
| 8-13 Hz | |||
|- | |||
| Beta | |||
| 13-30 Hz | |||
|} | |||
== Stages == | == Stages == | ||
=== REM === | |||
The defining characteristic of REM sleep is that eye movement is constant and fast. The brainwaves during REM sleep are similar to wakefulness. REM sleep is associated with muscle relaxation, long visual emotional vivid dreams disconnected from daily life, increased pulse, blood pressure, brain metabolism, and levels of [[Wikipedia:Acetylcholine|acetylcholine]]. [significance?] [vital?] | |||
=== NREM1 === | === NREM1 === | ||
Non-REM sleep stage 1, also called light sleep, is the lightest stage of sleep and comprises around 5% of total sleep time. It generally lasts around 1-5 minutes. | Non-REM sleep stage 1, also called light sleep, is the lightest stage of sleep and comprises around 5% of total sleep time. It generally lasts around 1-5 minutes. In light sleep, the sleeper may be aware, and believe themselves to be awake. [source] [PSG characteristics] [notable events and happenings] [significance?] [vital?] | ||
=== NREM2 === | |||
[definition] [PSG characteristics] [notable events and happenings] [significance?] [vital?] | |||
=== NREM3 === | |||
[definition] [PSG characteristics] [notable events and happenings] [significance?] [vital?] | |||
== Cycles == | == Cycles == | ||
Stages are arranged in repeating cycles, typically lasting around 90 minutes ± 20 minutes. [what order of sleep stages?] [differences between consecutive sleep stages] | |||
== Effects and functions == | == Effects and functions == | ||
| Line 21: | Line 47: | ||
== References == | == References == | ||
* {{Cite book| edition = 5th| publisher = McGraw-Hill medical| isbn = 978-0-07-139011-8| title = Principles of neural science| location = New York| date = 2013 |chapter=51. Sleep and Dreaming}} | * Information about EEG from: {{Cite book| edition = 5th| publisher = McGraw-Hill medical| isbn = 978-0-07-139011-8| title = Principles of neural science| location = New York| date = 2013 |chapter=50. Seizures and Epilepsy}} | ||
* {{Cite book| publisher = StatPearls Publishing| last1 = Patel| first1 = Aakash K.| last2 = Reddy| first2 = Vamsi| last3 = Shumway| first3 = Karlie R.| last4 = Araujo| first4 = John F.| title = StatPearls| chapter = Physiology, Sleep Stages| location = Treasure Island (FL)| access-date = 2025-06-08| date = 2025| chapterurl = http://www.ncbi.nlm.nih.gov/books/NBK526132/| pmid = 30252388 | * Information on stages, cycles and characteristics from: {{Cite book| edition = 5th| publisher = McGraw-Hill medical| isbn = 978-0-07-139011-8| title = Principles of neural science| location = New York| date = 2013 |chapter=51. Sleep and Dreaming}} | ||
* General information from: {{Cite book| publisher = StatPearls Publishing| last1 = Patel| first1 = Aakash K.| last2 = Reddy| first2 = Vamsi| last3 = Shumway| first3 = Karlie R.| last4 = Araujo| first4 = John F.| title = StatPearls| chapter = Physiology, Sleep Stages| location = Treasure Island (FL)| access-date = 2025-06-08| date = 2025| chapterurl = http://www.ncbi.nlm.nih.gov/books/NBK526132/| pmid = 30252388}} | |||
<references /> | <references /> | ||
Latest revision as of 05:34, 9 June 2025
Activity and alertness is reduced during sleep. While sleep affects the entire body, it most strongly affects the nervous system. Many important bodily functions, like waste cleanup and memory processing are supported by sleep. There are two kinds of sleep: rapid eye movement (REM) sleep and non-REM sleep. Non-REM Sleep has stages, which start at light sleep and progressively get deeper. In REM sleep, the eyes move quickly, notably, most dreams occur in it. NREM sleep stages are numbered from 1 to 3, from lighter to deeper. REM and Non-REM sleep alternates, repeating in cycles of around 90 minutes.
Measurement
Sleep originates in the brain. The brain communicates within itself using electrical signals, they can be measured using electroencephalography (EEG), where electrodes are attached to the scalp and the resulting signals are measured. Additionally, eye movement is an indicator of sleep, we can measure the electrical signals causing eye movements using electrooculography (EOG), which involves attaching electrodes around the eye. Finally, skeletal muscle movement can also be used to measure sleep, and by attaching electrodes to skeletal muscle, its activation can be measured as an electrical signal, this is called electromyography (EMG). Other tests are also performed, however, these three are most useful to distinguish sleep stages. Together, these methods are called polysomnography (PSG).
Brainwaves
Brainwaves, or neural oscillations, are repeating patterns visible in EEG. Normally, EEGs show activity in frequencies ranging between 1 and 30 Hz and 20 to 100 μV. There are different named categories of neural oscillations characterized by frequency. When awake and alert, an EEG shows high-frequency, low-voltage oscillations, while alpha waves are produced during relaxation.
| Name | Frequency range |
|---|---|
| Delta | 0.5-4 Hz |
| Theta | 4-7 Hz |
| Alpha | 8-13 Hz |
| Beta | 13-30 Hz |
Stages
REM
The defining characteristic of REM sleep is that eye movement is constant and fast. The brainwaves during REM sleep are similar to wakefulness. REM sleep is associated with muscle relaxation, long visual emotional vivid dreams disconnected from daily life, increased pulse, blood pressure, brain metabolism, and levels of acetylcholine. [significance?] [vital?]
NREM1
Non-REM sleep stage 1, also called light sleep, is the lightest stage of sleep and comprises around 5% of total sleep time. It generally lasts around 1-5 minutes. In light sleep, the sleeper may be aware, and believe themselves to be awake. [source] [PSG characteristics] [notable events and happenings] [significance?] [vital?]
NREM2
[definition] [PSG characteristics] [notable events and happenings] [significance?] [vital?]
NREM3
[definition] [PSG characteristics] [notable events and happenings] [significance?] [vital?]
Cycles
Stages are arranged in repeating cycles, typically lasting around 90 minutes ± 20 minutes. [what order of sleep stages?] [differences between consecutive sleep stages]
Effects and functions
[functions of sleep] [effects on particular conditions]
References
- Information about EEG from: "50. Seizures and Epilepsy". Principles of neural science (5th ed.). New York: McGraw-Hill medical. 2013. ISBN 978-0-07-139011-8.
- Information on stages, cycles and characteristics from: "51. Sleep and Dreaming". Principles of neural science (5th ed.). New York: McGraw-Hill medical. 2013. ISBN 978-0-07-139011-8.
- General information from: Patel, Aakash K.; Reddy, Vamsi; Shumway, Karlie R.; Araujo, John F. (2025). "Physiology, Sleep Stages". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID 30252388. Retrieved 2025-06-08.
