Lecture 8: Sleep Flashcards
Name five aspects of the nature of sleep.
Specific position, reduced reaction, inactivity, reversible and comfort.
How many sleep stages are there? What are their names and main features? How does the EEG look like?
There are four Non-REM stages of increasingly deeper sleep and the REM stage. Light sleep (stage I): rolling eye movements and slight slowing in EEG.
Stage II: easy to awake someone; includes K-complex and sleep spindles.
Stage III: slow delta activity, 20-50% (SWS1); amplitude gets larger, frequency lower.
Stage IV: slow delta activity, > 50% (SWS2); strongest waves the brain can produce.
REM: jerky eye-movement, EEG resembles wakefulness with low amplitude.
How long does it take to go through all sleep stages (thus, one complete cycle)? How many cycles are there per night on average?
It takes about 90 minutes. This cycle will reoccur about five times each night.
What is the role of the hypothalamus in sleep wake regulation? How does activity in the thalamus look like during sleep?
The hypothalamus is controlling sleep and can be considered the ‘sleep-wake switch’. During sleep, the thalamus becomes largely inactive.
Describe the role of the thalamus, the suprachiasmatic nucleus (SCN) and the brainstem in sleep-wake regulation.
Thalamus: involved in cortical activation, sleep spindles and EEG synchronization.
SCN: circardian clock.
Brainstem: ascending cortical activation, switch for REM/SWS.
Explain the role of GABA, Histamine and Acetylcholine in NonREM sleep regulation.
GABA inhibits posterior hypothalamus, inducing sleep. In this way, the excitatory histamine, responsible for cortical, thalamic and brainstem innervation, is down-regulated. Acetylcholine, responsible for innervation of the thalamus, is normally produced in upper brainstem areas, but release is inhibited by lack of histamine, when GABA acts upon the posterior hypothalamus.
Roughly explain the neurotransmitter processes in the brainstem for REM sleep.
During REM sleep, there is high brainstem activity, however only acetylcholine reaches forebrain (thalamus). Again, this process is influenced by GABA activity, yet, not in the hypothalamus but in the reticular formation of the brainstem. Glutamate activates phasic eye-movement, while glycine inhibits tonic muscle activity (sleep paralysis).
Describe how the amount of nonREM and REM sleep develops during the process of aging.
At an early age the amount of REM sleep is very high with hardly any nonREM sleep. However, while growing older, the amount of REM sleep continuously decreases, while nonREM sleep increases. REM sleep remains fairly stable with the end of puberty, while nonREM sleep already stabilizes at about 6 months of age.
Regarding mortality, what is the amount of sleep that is the least associated with dying earlier?
The amount is about 6,5 hours per day, with a significant increase from 8 hours on. (However, causality unclear!).
Name the main functions of sleep.
Physical restorative, synaptic downscaling, energy saving, cognitive function, emotional function (process emotions and protect against future negative ones) , immune function and brain ‘rinsing’.
Name respectively two disorders that are associated with low amount of sleep and with high amount of sleep.
Insomnia and Restless-Leg Syndrome (low)
Narcolepsy, Hypersomnia (high)
Describe the main features of insomnia.
Three months or more of disturbed sleep, prevalence estimated between 10% (more probable) and 30%, effect on awake functioning.
Name three causes for insomnia.
(1) Neurological disorder: e.g. Alzheimer’s disease.
(2) Primary or Psychophysiological insomnia.
(3) Psychological / psychiatric problem: e.g. depression.
Name the main symptoms of narcolepsy as well as its underlying mechanism.
Excessive sleepiness during day-time, sometimes cataplexy, as well as other REM sleep phenomena such as sleep paralysis or hypnagogic hallucinations. Narcolepsy is a result of a hypocretin / orexin deficiency leading to a very unstable balance between GABA and histamine leading to fast switches between phases of sleep and wakefulness.
On which receptor type do benzodiazepines act upon?
GABA-A receptors are modulate.
