Sleep

Snapshot

• A 19-year-old woman presents with chronic fatigue. She reports feeling very sleepy throughout the day, has been told that she would doze off, and then eventually drop her head on to the desk. She notes periods of not being able to move after waking up and fell to the ground after being excited at the news of her sister’s pregnancy. What frightened her the most are the vivid “visions” she would get when she is about to fall asleep.  

Sleep Physiology: An Introduction

Sleep physiology is the scientific study of the mechanisms and processes that regulate sleep. It encompasses the different stages of sleep, brain and body processes involved, and factors influencing sleep patterns. Sleep is categorized into rapid eye movement (REM) and non-rapid eye movement (NREM) stages, each serving unique functions. The sleep-wake cycle is regulated by the body’s internal clock, the circadian rhythm. Sleep physiology explores neurotransmitters, hormones, and brain regions involved in sleep induction, maintenance, and transitions between sleep stages. Understanding sleep physiology is crucial for promoting healthy sleep habits and addressing sleep-related disorders.

Sleep Stages

Sleep Stage	Description	EEG Waveform
	Awake and alert	Beta
	Awake and eyes closed	Alpha
Stage N1	Light sleep	Theta
Stage N2	Deeper sleep	Sleep spindles and K complexes
Stage N3	Deepest non-REM sleepSleepwalkingNight terrorsBedwetting	Delta
REM	Dreaming	Beta

• Suprachiasmastic nucleus of the hypothalamus is involved in circadian rhythm regulation
• GABA agonists (alcohol, benzodiazepines, and barbiturates) reduce REM and delta sleep

Sleep Physiology: Presentation

Introduction:

• Importance of sleep for overall health and well-being
• Overview of sleep physiology as the study of sleep mechanisms and processes

Sleep Stages:

• Explanation of rapid eye movement (REM) and non-rapid eye movement (NREM) sleep
• Characteristics and functions of each sleep stage (N1, N2, N3, REM)

Sleep Induction and Regulation:

• Neurotransmitters and hormones involved in sleep induction
• Role of the pineal gland in melatonin production
• The impact of the circadian rhythm on sleep-wake cycles

Sleep Architecture:

• Brainwave patterns during different sleep stages (alpha, theta, delta)
• Sleep cycle duration and frequency throughout the night

Sleep Disorders:

• Common sleep disorders (insomnia, sleep apnea, narcolepsy)
• Effects of sleep disorders on overall health and daily functioning
• Treatment options for managing sleep disorders

Factors Influencing Sleep:

• Environmental factors (light, noise, temperature)
• Lifestyle factors (exercise, caffeine, alcohol)
• Psychological factors (stress, anxiety, mood)

Conclusion:

• Recap of key points on sleep physiology
• Emphasize the importance of healthy sleep habits
• Encourage further exploration and understanding of sleep for optimal well-being.

REM Sleep

• Description
  • dreaming
  • loss of motor tone
  • may serve a memory processing function
• Physiology
  • same EEG pattern as when awake
    • therefore called “paradoxical sleep” or “desynchronized sleep”
  • rapid eye movement
    • defining feature of REM sleep
    • due to activity of paramedian pontine reticular formation
  • erection
  • ↑ and variable pulse and blood pressure
  • loss of muscle tone
• Neurotransmitters
  • acetylcholine is the principle neurotransmitter
  • norepinephrine, serotonin, and histamine suppress REM sleep
    • therefore, certain antidepressants (eg, SSRI, SNRI) can pharmacologically suppress REM sleep
• Timing
  • occurs every 90 min
  • duration ↑ with every cycle
• amount of REM sleep ↓ with age

Sleep Disorders

• Narcolepsy 
  • disordered regulation of sleep cycles secondary to loss of orexin (hypocretin) neuropeptides
  • excessive daytime sleepiness
  • sleep paralysis
  • may include hallucinations
    • hypnagogic
      • just before sleep
    • hypnopompic
      • just before awakening
  • nocturnal and narcoleptic sleep episodes start off with REM sleep
  • cataplexy
    • loss of all muscle tone following a strong emotional stimulus
    • only some patients
    • patients have undetectable hypocretin-1 in levels in CSF 
  • stong genetic component
  • REM sleep within 15 minutes of sleep onset 
  • treatments 
    • stimulants
      • e.g., modafinil (first-line) and amphetamines (generally second-line)
    • cataplexy
      • serotonin and dopamine reuptake inhibitor
• Sleep apnea
  • see Sleep Apnea 

Sleep Physiology: Treatment

The treatment of sleep-related issues and disorders is an essential aspect of sleep physiology. Effective management strategies aim to improve sleep quality and address underlying causes. Treatment options may vary depending on the specific sleep disorder, but here are some common approaches:

1. Sleep Hygiene: Promoting healthy sleep habits, such as maintaining a consistent sleep schedule, creating a comfortable sleep environment, and practicing relaxation techniques.
2. Cognitive-Behavioral Therapy for Insomnia (CBT-I): A structured therapy that helps individuals identify and modify thoughts and behaviors contributing to insomnia, promoting better sleep.
3. Medications: Prescription medications may be prescribed for certain sleep disorders, such as insomnia or narcolepsy, to regulate sleep patterns or address underlying causes.
4. Continuous Positive Airway Pressure (CPAP): A common treatment for obstructive sleep apnea, involving the use of a machine that delivers air pressure to keep the airways open during sleep.
5. Light Therapy: Used to regulate circadian rhythms and treat conditions like seasonal affective disorder (SAD) by exposing individuals to bright light at specific times of the day.
6. Surgical Interventions: In some cases, surgical procedures may be necessary to address anatomical abnormalities that contribute to sleep disorders, such as sleep apnea.

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