How does the brain control sleep and wake?
Transcript of How does the brain control sleep and wake?
How does the brain control sleep and wake?
Nina Vujovic
Program in NeuroscienceHarvard Graduate School of Arts and Sciences
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Signals from deep brain to cortex keeps us alertIn brown aredopaminergicprojections to the cerebral cortex.
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A cluster of vital arousal-promoting neuronsIn yellow arehistaminergric projections tothe cerebralcortex. Anti-histamines,found in someallergy medications,make you drowsy becausethey block thissignal.
X
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What if the sleep-promoting VLPO signal is disrupted?
• Aging leads to VLPO neuron loss– Problems sleeping more common among elderly
http://lua.weblog.com.pt/CAFFEINE.JPG
• Animals with VLPO injuries sleep only 50% as much as normal animals
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Sleep - Wake Transitions
• We don’t spend much time in drowsy in-between states
• But what keeps us from flipping back and forth between sleep and wake all the time?
Sleep-promoting VLPO
wake-promoting system
vs.
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What governs timing of sleep?• Energy regulation system
• Circadian timing system
Reset with light
Recharge with sleep
Quick fix:
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-
A P P P
Runs with near 24-hour period
Does this even in the absence of light cycle
P P P
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Adenosine tri-phospate Adenosine binds to neuronsand makes us feel tired. Caffeine blocks this interaction, actingto trick our brain into thinkingwe are not tired.
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Four major ways to mess with sleep
1. Forced schedule that goes against circadian and energy regulation systems
2. Injury to neurons that regulate sleep
3. Drugs that mimic neurotransmitters
4. Unusual circumstances
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Unusual circumstances:• Unusual or uncomfortable environment• Low oxygen/high CO2/breathing problems
Zzzzz ZzZZZZ <gasp>
* *
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Unusual circumstances:• Unusual or uncomfortable environment• Low oxygen/high CO2/breathing problems• Inner ear issues/zero gravity
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Unusual circumstances:• Unusual or uncomfortable environment• Low oxygen/high CO2/breathing problems• Inner ear issues/zero gravity• Gastrointestinal/urological problems
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Unusual circumstances:• Unusual or uncomfortable environment• Low oxygen/high CO2/breathing problems• Inner ear issues/zero gravity• Gastrointestinal/urological problems• Severe hunger, pain or stress
Owww!
ooof…
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Summary
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• deep brain arousal-promoting neurons stimulate cortex to promote wakefulness
• VLPO inhibits these neurons to promote sleep• orexin neurons help consolidate wakefulness• circadian and energy regulation systems govern timing
and duration of sleep• unusual circumstances, brain injuries, or drugs can
override VLPO signal and disrupt sleep• understanding these systems better may lead to new
treatment or prevention options for sleep disorders
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