Neurology 16 - Sleep Flashcards
Which stages are non-REM/slow wave?
- Stages 1 to 4
- From drowsiness, through light sleep to deep sleep
Describe the EEG rhythm in non-rem sleep
Slows gradually from theta when awake (4-8Hz) to delta (0.5-4Hz)
Describe the muscle tone and eye movements in non-rem sleep
- General muscle tone decreases gradually
- Relatively few eye movements
What happens in REM sleep?
- EEG speeds up to Beta (13-30Hz)
- Low general muscle tone
- Rapid eye movements
- Dreams are most prominant and most easily recalled
What is active during dreams?
- Limbic system
- Frontal cortex is less active
What are sleep cycles?
- Passage through the 5 stages of sleep
- Several sleep cycles in an average nights sleep
- Lasts around 90 mins
- Heart rate and respiration rate change in synchrony (increases during REM)
List the main pathways involved in the sleep wake cycle
- Reticular activating system (maintains arousal)
- Hypothalamic nuclei (control activity of the RAS)
- Caudal pontine reticular formation
What is the reticular activating system made of?
- Nuclei in the brainstem
- Raphe nuclei, nucleus coeruleus and colinergic nuclei
- Projects upwards directly or indirectly via the thalamus to all areas of the cerebral cortex
List the components of the hypothalamic nuclei. What is their role in the sleep wake cycle?
- Lateral hypothalamus promotes wakefulness (orexin/hypocretin)
- Ventrolateral preoptic nucleus promotes sleep (anterior hypothalamus)
What is the function of the caudal pontine reticular formation?
- Active during REM sleep
- Suppresses general muscle tone
- Activates rapid eye movements
Describe the process of circadian control
- Special cells in the retina detect decrease in light level, and activate the suprachiasmatic nucleus of the hypothalamus
- Suprachiasmatic nucleus modulates sleep-wake circuits and stimulates the pineal gland to secrete melotonin
- Melotonin syncronises physiological processes with day length
List the evidence that sleep is necessary
- Highly conserved during evolution (most/all animals sleep)
- Sleep deprivation has detremental effects on life
- Regulated very accurately
List the possible functions of sleep
- Restoration and recovery
- Energy conservation (10% drop in BMR)
- Predator avoidance
- Memory consolidation
- Effects on brain function
List the sleep disorders
- Insomnia (too little sleep)
- Narcolepsy (too much sleep)
- Hypersomnia (excessive daytime sleepiness)
What is the prevalence of insomnia?
- 20-50% of the general population
List the causes of insomnia
- Most cases are transient (stress/emotional disturbance)
- Some cases have a physiological cause (sleep aponea or chronic pain)
- Some cases are due to brain dysfunction (depression, fatal familial insomnia)
How is insomnia treated?
- Hypnotics, which enhance GABAergic circuits
- Sleep hygiene
- Sleep CBT
What is the cause of narcolepsy?
- Genetic deficiency in orexin or hypocretin
- Enter REM sleep directly and repeatedly throughout the day
How is narcolepsy treated?
- Sleep management or stimulants
- Eg. Amphetamine
What can shift work (sleeping at the wrong time) lead to?
Increased risk of certain conditions
- Diabetes
- Obesity
- Cancer
List the behavioural criteria for sleep
- Stereotypic or species-specific posture
- Minimal movement
- Reduced responsiveness to external stimuli
- Reversible with stimulation (unlike coma, anaethesia or death)
How is sleep monitored?
- EEG (brain)
- Electrooculogramm (eyes)
- EMC (muscle)
List the stages of sleep
- Awake (EEG, EOG and EMG are active)
- Stage 1 & 2 are non-REM (lowest EEG, EOG and EMG activity)
- Stage 3&4 (non-REM - large slow changes in EEG)
- Stage 5 (REM - highest EOG, EEG rapid activity like in the awake stage)
How does EEG change during sleep?
- Becomes slower to stage 5
- Speeds up in REM sleep to be similar to that when awake
