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Sleep and Wakefulness Disorders

Terms in this set (32)

What is "Homeostatic sleep drive" dependent upon?
- Adenosine
- GABA
What is "Circadian wake drive" dependent upon?
Light-stimulating hypocretin/orexin
What 5 NTs are involved in the arousal spectrum?
- Dopamine
- Histamine
- Norepinephrine
- Serotonin
- Acetylcholine
What are the brain circuits of the arousal spectrum called, collectively?
Ascending Reticular Activating System
What are the 3 stages of Homeostatic sleep drive?
1. Adenosine builds up the longer we are awake

2. Homeostatic sleep drive increases until hypothalamus is triggered to release GABA

3. GABA release inhibits the wake-promoting circuit in many areas of the brain
Adenosine acts as a ____________ to promote ________ and suppress ________.
- Neuromodulator
- Promote sleep
- Suppress arousal
What is the most powerful synchronizer of Circadian wake drive?
Light
What is called "the brain's internal clock?"
Suprachiasmatic Nucleus (SCN)
During periods of darkness, the SCN induces the release of ____________.
Melatonin
During periods of light, melatonin is __________.
suppressed
Stages of Circadian wake drive
1. SCN receives light (or dark)
2. Histamine is released during periods of light (inhibits GABA)
3. Histamine stimulates release of hypocretin/orexin
4. Hypocretin then causes...
- Release of ACh
- Release of DA
- Release of NE
- Release of 5HT
Bullets about GABA
- Amino acid, all over brain
- Chief inhibitory NT
- Enhanced by mood stabilizers = decreased arousal
- Causes relaxation
- Slows breathing
What is the key NT that regulates wakefulness?
Histamine

- Two receptors for wakefulness
H1 (postsynaptic) = wakefulness and alertness
H3 (presynaptic) autoreceptor = turns off histamine, causes wakening
What happens to GABA during sleep?
- Increases for first couple of hours

- Then plateaus

- Then starts to decline
What happens to hypocretin/orexin during sleep?
- Decline

- Then plateau

- Then increase steadily
What happens to Acetylcholine during sleep?
Fluctuate throughout night

- Lowest during stage 4
- Highest during REM sleep
What happens to DA, NE, and 5HT during sleep?
Fluctuate throughout night

- Lowest during REM sleep
- Highests during stage 2
What fires in phases to maintain arousal throughout the day?
Hypocretin/orexin

- More rapid bursts after stimulus (hunger, cold, stress, etc.)

- Also facilitates goal-directed behaviors such as increased food intake
Where is the sleep/wake "OFF" (sleep) switch located, and what regulates it?
- Ventrolateral preoptic nuclease (VLPO) of hypothalamus

- GABA
Where is the sleep/wake "ON" (wake) switch located, and what regulates it?
- Tuberomammillary nucleus (TMN) of hypothalamus

- Histamine
What are the 5 stages of sleep?
I: drowsy (light sleep)
II: increase sleep spindles (light sleep)
III: moderate to deep sleep
IV: deepest level of sleep (slow wave)
REM: vivid dreams occur
Two types of Insomnia Disorder

Plus two durations...
Primary: too much arousal both at night and during day
- not usually sleepy during day

Transient: caused by stress, jet lag, etc
- generally relieved with exercise, environment changes

Short-term: up to 3 wks
Long-term: more than 3 wks
More than _____% of psychiatric disorders have insomnia as a symptom
50%
When insomnia circuits are effective, ________ neurons filter out most sensory input
GABA
If __________ projections are hypoactive during the day, the GABA filter may not allow enough sensory info to reach the cortex
Dopamine

- so, excessive daytime sleepiness can occur

- enhancing DA during the day helps normal wakefulness
What may help Phase Delayed Circadian Rhythm?
- morning light

- evening melatonin

(common in adolescents and depression)
What may help Phase Advanced Circadian Rhythm?
- evening light

- morning melatonin

(common in elderly)
Hypersomnia
- long sleep duration
- daytime sleepiness
- latency < 8 minutes
- lasts at least 3 months
- often accompanied by memory/attention issues, GI issues, depression, anxiety
- should refer to PSG
Kleine-Levin Syndrome
- recurrent hypersomnia
- excessive daytime sleepiness
- hyperphagia
- hypersexuality
- cognitive/mood disturbances
- mostly adolescent boys
- etiology might be viral; subsequent autoimmune reaction
Narcolepsy
- excessive daytime sleepiness
- w/ or w/out cataplexy
- abnormal REM manifestations
- intrusion of sleep while awake
- hypnopompic hallucinations present upon waking
- should refer to PSG
Narcolepsy has profound loss of _______________ neurons
hypocretin/orexin

(so, inability to stay awake)
Sleep Assessment Tools
- Insomnia Severity Index (sleep problems)
- Pittsburgh Sleep Quality Index (sleep quality)
- CAPS Sleep Items (nightmares, PTSD)
- Epworth Sleepiness Scale (narcolepsy)
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