Sleep Flashcards
What is sleep? What does it involve?
- Stereotypic or species-specific posture
- Minimal movement
- Reduced responsiveness to external stimuli
- Reversible with stimulation – unlike coma, anaesthesia or death
What measurements are used to evaluate sleep / sleep patterns?
EEG (brain waves)
EOG (eye movements)
EMG (muscle movements -> jaw)
What are the stages of sleep?
- awake
- Stage 1&2 (NREM)
- Stage 3&4 (NREM)
- Stage 5 (REM)
What does REM stand for?
Rapid Eye Movement
What is a common characteristic of stage 2 sleep on the EEG?
sleep spindle
How is sleep structured?
- divided into 5 stages
- multiple sleep cycles
When are you most likely to dream?
- during REM sleep but not exclusively
What are lucid dreams?
In the dream you are aware that you are dreaming
How is sleep controlled?
- the RAS is important for enabling conciousness
- Lateral hypothalamus: promotes wakefulness, suppresses RAS
- ventrolateral preoptic nucleus: promotes sleep, suppresses RAS
RAS
- Reticular activating system
- projections from brainstem to thalamus and cortex
- it is not the center of conciseness. It enables conciseness, without it consciousness would not be possible.
- > stimulated by lateral hypothalamus
- > suppressed by ventrolateral preoptic nucleus.
What do different sleep phases look like on EEG, EMG, EOG?
- rapid eye movement in Stage 5, looks like in awake
- higher heart rate and breathing rate in REM
- overall slowing EEG in the sleep stages until REM sleep is reached and increased EEG speed
SCN
= suprachiasmatic nucleus
- tracks level of ambient light (“clock”)
- has connections to LH, VLP, RAS and the pineal gland (melatonin release)
- synchronises sleep with falling light level
- regulates the circadian rhythm
Pineal gland
- responsible for melatonin release
- stimulated by the SCN
Lateral Hypothalamus
- promotes wakefulness (orexin, hypocretin)
Ventrolateral preoptic Nucleus
- (in anterior hypothalamus)
- promotes sleep
What are indices that sleep is necessary?
- Most/all animals sleep
- Sleep deprivation is detrimental
- Sleep is regulated accurately
What are the psychiatric and neurological consequences of sleep deprivation?
– Sleepiness
- irritability
- stress
- mood fluctuations
- depression
- impulsivity
- hallucinations
- psychosis
- seizures (especially in epilepsy but also in healthy poeple)
What are the neurological consequences of sleep deprivation?
– Impaired attention, memory, executive function
– Risk of errors and accidents (e.g. shift work, doctors)
– Neurodegeneration (?)
What are the somatic complications of sleep deprivation?
– Glucose intolerance – Reduced leptin/increased appetite – Impaired immunity – Increased risk of cardiovascular disease and cancer – Death
What is sleep important for?
- normal brain funciton
- memory consolidation
- e.g. affected brain activation when solving math problems in a sleep deprived state.
How is sleep regulated? I.e. what happens after sleep deprivation?
After sleep loss:
• Reduced latency to sleep onset
• Increase of slow wave sleep (NREM)
• Increase of REM sleep (after selective REM sleep deprivation)
What are the functions of sleep?
- Restoration and recovery – but active individuals do not sleep more
- Energy conservation – 10% drop in BMR – but lying still is just as effective
- Predator avoidance – but why is sleep so complex?
- Specific brain functions – memory consolidation, …
What are dreams? When do they occur?
- Can occur in REM and NREM sleep
- Most frequent in REM sleep
- More easily recalled in REM sleep
- Contents of dreams are more emotional than ‘real life’
- Brain activity in limbic system higher than in frontal lobe during dreams
What is the function of dreams?
- Safety valve for antisocial emotions
- Disposal of unwanted memories
- Memory consolidation
(Freud? - dealing with problems, anxiety)
