Sleep Flashcards
What is the behavioural criteria for sleep
Altered consciousness
Decreased sensory and motor activity
Decreased ability to respond to environmental stimuli
Reversible with stimulation – unlike coma, anaesthesia or death
What are the stages of sleep
- Awake
- Stage 1 + 2 NREM
- Stage 3 + 4 NREM
- Stage 5 REM
What is the psychological criteria for sleep
Brain activity - electroencephalogram
Eye movements - electrooculogram
Muscle - Electromyogram
Describe the sleep cycle
Transitioning from wakefulness into NREM sleep (4 stages)
Usually lasts 90 minutes
Good night’s sleep will usually consist of 4-6 complete sleep cycles
Amount of time spent in deep sleep is highest earlier in the night, and reduces with each sleep cycle and reduces with each sleep cycle.
The period of REM sleep gets progressively longer with each sleep cycle
Describe the EEG, EOG and EMG recordings when awake
EEG – fast brain rhythm – beta waves (~30 Hz)
EMG – reasonable amount of muscle tone because you are maintaining posture and ready for action
Describe the structure of sleep
around 5 cycles of the stages with 5 REM stages
Describe the maintenance of arousal
Reticular activating system controls consciousness.
Begins in the brainstem and projects upwards
Lateral hypothalamus promotes wakefulness (orexin/hypocretin)
Ventrolateral pre-optic nucleus/anterior hypothalamus promotes sleep
what are the psychiatric and neurological effects of sleep deprivation
Sleepiness Irritability Stress Mood fluctuations Depression Hallucinations
What are the neurological effects of sleep deprivation
Impaired attention, memory, executive function
Risk of errors and accidents
Neurodegenerations
What are the somatic effects of sleep deprivation
Glucose intolerance Reduced leptin/increased appetite Impaired immunity Increased risk of cardiovascular disease and cancer Death
Describe three ways in which sleep is regulated after sleep deprivation.
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 (lying still is just as effective)
Specific brain functions – memory consolidation
(Predator avoidance)
When do dreams occur during sleep
Can occur in REM and NREM, more frequent in REM
More easily recalled in REM
What are the functions of dreams
Safety valve for antisocial emotions
Disposal of unwanted memories
Memory consolidation
What are the causes of chronic insomnia
Physiological e.g. sleep apnoea, chronic pain
Brain dysfunction e.g. depression, fatal familial insomnia, night working
What is the treatment for insomnia
Sleep hygiene
Hypnotics (most enhance GABAergic circuits)
Sleep CBT
How can sleep hygiene be improved
establishing fixed times for going to bed/waking up
creating a relaxing bedtime routine
only going to bed when you feel tired
maintaining a comfortable sleeping environment
not napping during the day
avoiding caffeine, nicotine and alcohol late at night
avoiding eating a heavy meal late at night
don’t use back-lit devices shortly before going to bed
What are some causes of hypersomnia
Narcolepsy
Idiopathic hypersomnolence
Post-traumatic brain injury
Secondary causes (poor night sleep)
Obstructive sleep apnoea
Nocturnal pain e.g. diabetic neuropathy/arthritis
Anxiety
Medication
Restless legs syndrome and limb movements in sleep
What diagnostic tool can be used to help for sleepiness
Epworth sleepiness scale
Describe narcolepsy
Falling asleep repeatedly during the day and disturbed sleep during the night
Cataplexy (sudden, brief loss of voluntary muscle tone, triggered by storm emotions e.g. laughter)
Dysfunction of control of REM sleep
Orexin/hypocretin deficiency
What is the effect of shift work on sleep
Night working causes physiological processes to be desynchronised
Leads to sleep disorders, fatigue and an increased risk for some conditions (obesity, diabetes and cancer)
Describe the EEG, EOG and EMG recordings in stage 1 + 2 sleep
Light sleep
EEG – theta (4-8 Hz) waves – gradually becoming more and more drowsy
EOG – NO eye movements
EMG – muscle activity reduced considerably
Describe the EEG, EOG and EMG recordings in stage 3 + 4 sleep
Very deep sleep
EEG - Delta activity (< 4 Hz)
EOG – minimal eye movement
EMG – continued relaxation of muscles
Describe the EEG, EOG and EMG recordings in stage 5 sleep
EOG activity increases greatly
EEG is similar to that of awake
Describe how heart rate and respiratory rate change during sleep
SLOW during NREM
FAST during REM sleep
Describe the circadian synchronisation of the sleep-wake cycle.
The suprachiasmatic nucleus - synchronisation with falling light level
It receives an input from the retina (not from the usual photogenic cells) and as light level falls the suprachiasmatic nucleus becomes more active
Describe the effect of the suprachiasmatic nucleus on the nuclei within the hypothalamus.
Falling light level –> increased activity of suprachiasmatic nucleus
This leads to activation of ventrolateral preoptic nucleus and inhibition of lateral hypothalamus so you become sleepier
What other important projection does the suprachiasmatic nucleus have and what is the importance of this projection?
Projection to the pineal gland
Increase in suprachiasmatic nucleus activity leads to activation of pineal gland so that it releases melatonin
Melatonin adjusts various physiological processes in the body that fit with sleep
