Sleep Flashcards
Sleep
- reversible behavioral state of perceptual disengagement from, and unresponsiveness to the environment
- essential for heath in all mammals (sleep deprivation can be fatal)
- not absence of all brain activity, but series o complex, precisely regulated brain states that are activated & deactivated by multiple sets of diencephalic & brainstem nuclei
Sleep Demographics
- normal adults average 7.5 +/- 2 hrs per night
- sleep occupies approximately 1/3 of lifespan
- normal sleep duration dec. with inc. age
- sleep deprivation leads to decreased mental & physical performance & eventually death
Biological Clock
- group of cellular/molecular cycles inherent in a variety of body organs that drive a host of circadian rhythms
- contain + & - feedback loops that allow the mechanism to cycle with a regular time constant
Suprachiasmatic Nucleus
- anatomical pathway by which ambient light regulates melatonin synthesis and secretion
- rise of melatonin beginning in early evening as daylight wanes & peaking around 2-4 am
Polysomnography
-method of measuring sleep
Sleep Lab
- sleep room with wall mounts for connecting physiological monitors to the patient
- monitors air flow of nose
- scalp to monitor EEG, face sensors to monitor eyelid movement, monitor respiration, monitor blood ox
Sleep frequencies
- 5 stages (changes of EEG)
- Beta > 13 Hz
- Alpha 8-13 Hz
- Theta 4-7 Hz (stage I & II)
- Delta <4 Hz (stage III & IV)
-alpha & beta normal awake humans
REM stage
- 5th
- Rapid Eye Movement
- associated eye movements, physiological changes
- EEG characteristics: fast frequency, low voltage, close to awake state
- theta and beta
Sleep Stages (Cycle)
Stage I - IV Non Rapid Eye Movement Sleep or NREM sleep & stage V is rapid eye movement REM
- Frequency (hertz, cps) and voltage
- Stage I sleep is lightest sleep and stage IV is deep sleep
- Stage II is characterized by bursts of activity called sleep spindles and K complexes
Stage II Sleep
-unique “spindle” and “K-complex” patterns
Sleep Cycle
- starts with Stage I and ends with REM sleep (90 min)
- during duration of stages 3 & 4 sleep lasts longer early in the sleep cycle while REM sleep duration & frequency increase toward the morning or waking hours
- tend to be 5-6 cycles of NREM and REM sleep during a 7-8 hr sleep period
Physiologic Changes in Sleep Cycle: NREM sleep
- few eye movements, when they occur they are slow, rolling
- decreased muscle tone but movement still occurs
- decreased HR, BP, RR, temp, metabolic rate
- dreams occur but they are less vivid with low emotional content
- sleep walking and night terrors occur during slow wave sleep
- all changes reach a maximum during stage IV sleep
Physiologic Changes in Sleep Cycle: REM sleep
- rapid, ballistic eye movements
- muscle paralysis
- HR, BP, RR, temp., metabolic rate approach awake level
- dreams are vivid with strong emotional content, bizarre
- penile and clitoral erection in REM
Neural Sleep Circuits
-awake state: activation of the following nuclei promote wakefulness
Brainstem Nuclei:
-cholinergic neurons in pedunculopontine (PPT) and lateral-dorsal tegmental (LDT) areas
-noradrenergic neurons in the locus ceruleus
-dopaminergic neurons in substantia nigra
-serotonergic neurons in raphe nuclei
Hypothalamic Nuclei:
-histaminergic neurons in tuberomammillary nucleus
-orexin/hypocretin neurons in the lateral hypothalamus
Cholinergic Neurons
- from pedunculopontine (PPT) & lateral dorsal tegmental (LDT) areas project to the thalamus and other brainstem areas
- activation signals thalamic-cortical signaling with high frequency, low voltage EEG consistent with arousal and alertness
Noradrenergic Circuits
-imput from locus ceruleus to the neocortex is highly activated during wakefulness, less so during NREM sleep, and nearly silent during REM sleep
Serotonergic Circuits
- from dorsal and medial raphe nuclei are highly active during wakefulness, less during NREM sleep, and nearly silent during REM sleep
- variety of drugs influence sleep (tricyclic antidepressants & selective serotonin reuptake inhibitors (SSRIs)
Histaminergic Circuits
- out put from tuberomammillary nucleus is high during wakefulness, lower during NREM sleep, and still lower during REM sleep
- drugs that block histamine H1 reeceptors, such as diphenhydramine inc. NREM and REM sleep
Hypothalamic Nuclei
-suprachiasmatic & paraventricular nuclei involved in the light/dark regulation of pineal gland production of Melatonin
Somnogens
- endogenous sleep-promoting chemicals that may accumulate during wakefulness and promote sleep onset
- Adenosine: accumulates in CNS during wakefulness & declines during sleep
- Cytoines: IL-1B and TNF promotes sleep
- Melatonin: Synthesis turned on by dec. light
Sleep Symptoms
- Sleepiness
- Insomnia
- Snoring
- Abnormal Behaviors
- Nightmares
- Abnormal Movements
Multiple Sleep Latency Test
-EEG defined sleep latency, the time required to fall asleep measured during 4-5 daytime naps
Epworth Sleepiness Scale
-self-reported tendency to fall asleep in 8 different situations differing in their soporific nature
Obstructive Sleep Apnea (OSA)
-repetitive blockage of the respiratory pathway during sleep causing apneic periods lasting longer than 10 sec and causing oxyhemoglobin desaturations of more than 4%
OSA epidemiology
- 3-5% of population (4% men, 2% women age 30-60)
- more common in men
- incidence inc. with obesity but occurs also in the non-obese
- strong association b/w OSA, heart disease, HTN
OSA Pathogenesis
-complex interaction b/w pharyngeal muscles, tongue, and soft tissues leading to airway obstruction
OSA Physical Findings
- Nasal obstruction
- Tonsillar/adenoid hypertrophy
- macroglossia
- reflux laryngitis
- shirt collar size > 17 in
- hypothyroidism with goiter
- truncal obesity
- HTN
- congestive heart failure
- pitting edema of lower extremities
- enlargement of hands & feet (acromegaly)
OSA Symptoms
- excessive daytime fatigue
- snoring
- heartburn
- memory loss
- irritability
- depression
- morning headache
- shortness of breath
- nocturia
- impotence
Narcolepsy
- excessive daytime sleepiness associated with one or more of the following tetrad
- sleep attacks/intrusions, irresistible, daytime sleep onset
- cataplexy (abrupt loss of muscle tone during waking hours
- sleep paralysis - persistent REM sleep atonia after awakening
- hypnagogic hallucinations - dream persistent after awakening
Narcolepsy Epidemiology
- 0.05-0.2% (200,000 in US)
- symptom onset 90% develop symptoms by 2nd-3rd decade
- symptoms persist throughout life
- male = female
- familial tendency: 1st deg. relatives have 1-2% inc. risk
Secondary Narcolepsy
-associated with multiple sclerosis, pituitary tumors, vascular malformations, stroke
Narcolepsy Pathogenesis
- loss of hypocretin/orexin secreting neurons in the posterior lateral hypothalamus related to:
- HLA genes DQ1, DQB1*0602 that may predispose to an autoimmune attack on orexin secreting neurons
- secondary to tumor, stroke, to orexin secreting neurons
Naracolepsy Lab
- clinical presentation with components of tetrad
- low CSF hypocretin-1 level (10% normal)
- Polysomnography (mean sleep latency test - MSLT of < 8 min)
- sleep onset REM period >2 episodes of SOREMPs
Naracolepsy Treatment
- Daytime sleepiness - methylphenidate, Modafinil, Gama-hydroxybutyrate
- Cataplexy - tricyclic antidepressants, SSRIs
Insomnia
-difficulty falling asleep or remaining asleep
Epidemiology of Insomnia
- Transient insomnia - days to weeks; affects 50% of adults during lifetime
- Chronic insomnia - >6 weeks, affects 25% of adults
- Female: Male 1.3:1
- Strong association b/w insomnia & depression
Insomnia Causes
- delayed sleep onset
- primary: idiopathic, psychophysiologic
- secondary: anxiety, physical activity, jet lag, shift work, sedative withdrawal, stimulant drug use
- Failure to maintain sleep: obstructive sleep apnea, aging, sedative wear-off, depression, REM disorder, medication effects, CNS degenerations
REM sleep Behavior Disorder
-loss of atonia/paralysis during REM sleep leading to physical acting out of dream states including verbalization, punching, kicking, jumping from bed; this activity can cause physical injury to the bed partner or patient
REM sleep Behavior Disorder: Epidemiology
- RBD present in 0.5% of population
- most common in adult makes over 50
REM sleep Behavior Disorder: Pathogenesis
- primary RBD may be idiopathic or associated with alpha-synucleinopathies (parkinsons, multisystems atrophy, lewy body dementia, progressive supranuclear palsy)
- secondary RBD can be caused by EtOH withdrawal, TCA, and SSRI use
REM sleep Behavior Disorder: Treatment
-RBD responds well to Clonazepam
