Sleep Flashcards
What three techniques are used to monitor activity during sleep?
Electroencephalography (EEG) - evaluates electrical activity of brain. Electromyography (EMG) - electrical activity of muscle in response to stimulus. Electrooculography (EOG) - measuring the corneo-retinal standing potential that exists between front and back of human eye.
What is the behavioural criteria for sleep?
Stereotypic or species-specific posture. Minimal movement Reduced responsiveness to external stimuli. Reversible with stimulation - unlike coma, anaesthesia or death.
What are stages of sleep?
Stages 1 + 2 NREM Stages 3 + 4 NREM Stage 5 REM
Compare psychological measurements during stage 1 + 2
Light sleep
EEG theta waves (4-8Hz) - gradually more and more drowsy
EOG - no eye movements
EMG - reduced muscle activity from wake
Compare psychological measurements during stage 3 + 4
Very very deep sleep
EEG - delta activity <4Hz
EOG - minimal eye movement
EMG - continued relaxation of muscles
Compare psychological measurements during stage 5
REM sleep
EEG - brain shifts abruptly back to fast rhythm similar to awake state
EOG - rapid eye movement
EMG - muscle activity at its lowest - basically paralysed
How long is a sleep cycle?
1 to 1 and a half hours
When do we dream?
Usually during REM sleep however, it is not exclusive to REM
Heart rate also increases during REM sleep.
Compare the relative amounts of NREM and REM sleep in a sleep cycle at the start of a night’s sleep and at the end.
Start of the night – more NREM sleep
End of the night – more REM sleep
Describe how heart rate and respiratory rate change during sleep.
SLOW during NREM
FAST during REM sleep
What controls consciousness?
Reticular activating system which is found in the brainstem
What projections does RAS have?
Network of neurons located in the brainstem
anterior projections to the hypothalamus, direct to cortex, posterior to thalamus
How does the reticular activating system control the activity of the cortex?
Or via indirect connections through the intralaminar nuclei of the thalamus
In layman’s terms what does RAS do?
Turns the lights on
Enables consciousness to happen and controls it
What are the two important nuclei in the hypothalamus that are responsible for influencing the reticular activating system and, hence, regulating the sleep-wake cycle?
Lateral Hypothalamus – excitatory, promotes wakefulness via orexin/hypocretin neurotransmitter
Ventrolateral Preoptic Nucleus (anterior hypothalamus) – promotes sleep
NOTE: they have an antagonistic relationship
Describe the circadian synchronisation of the sleep-wake cycle.
The suprachiasmatic nucleus is responsible for synchronising the sleep-wake cycle with falling light level, pathway that produces melatonin (makes you sleepy) . Stimulates pineal gland to produce melatonin. (ALSO HYPOTHALAMUS)
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 à increased activity of suprachiasmatic nucleus
This leads to activation of ventrolateral preoptic nucleus and inhibition of lateral hypothalamus so you become sleepier
What are the effects of sleep deprivation?
Psychiatric and neuro - Sleepiness, irritability, stress, mood fluctuations, depression, impulsivity, hallucinations
Neurological - Impaired attention, memory, executive function
Risk of errors and accidents
Neurodegeneration (?)
Somatic - Glucose intolerance, Reduced leptin/increased appetite, Impaired immunity, Increased risk of cardiovascular disease and cancer, Death
How is sleep regulated accurately?
After sleep loss - reduced latency of sleep onset
increased slow wave sleep (NREM)
Increase of deep sleep ( after selective REM deprivation )
Describe the brain activity of the limbic system compared to the frontal lobe in sleep.
Brain activity in the limbic system is higher than in the frontal lobe
This is because the content of dreams tends to be more emotional than in real life
What was the perception of the function of sleep and how were these theories/thoughts disporved?
Restoration and recovery - more active individuals don’t 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 function - memory and consolidation THOUGHT TO BE A REAL PURPOSE
When are dreams easier to recall?
When they are in REM sleep but are not exclusive to REM
More emotional and sensationalised than real life.
What are the functions of dream?
- Safety valve for antisocial emotions
- Disposal of unwanted memories
- Memory consolidation
Sleep is important in memory consolidation. What is the difference in memory consolidation between NREM and REM sleep?
NREM – declarative = facts and events
REM – procedural = learning skills
Describe the incidence of insomnia
- High prevalence
- Most cases transient
What are some of the causes of chronic insomnia?
– physiological e.g. sleep apnea, chronic pain
– Brain dysfunction eg. depression, fatal familial insomnia, night working
What are treatments for insomnia?
sleep hygiene : Establish fixed times for sleep and wake, relaxing bedtime routine, only go bed when you feel tired, comfortable sleeping environment, not napping, avoid caffeine, don’t eat heavy meal, not using lit back devices before bed.
– hypnotics (most enhance GABAergic circuits)
– sleep CBT (cognitive behaviour therapy)
What is hypersomnia?
Excessive daytime sleepiness
secondary causes due to poor quality of overnight sleep - obstructive sleep apnoea, restless leg syndrome, nocturnal pain, neurodegenerative disease and some rarer causes being oseophageal acid reflux and severe bruxism
Narcolepsy is a primary cause of hypersomnia, what is it and give some other primary causes
Narcolepsy is a condition characterised by an extreme tendency to fall asleep whenever in relaxing surroundings. Leads to falling asleep repeatedly during the day and disturbed sleep at night. Cataplexy, dysfunction of REM and orexin/hypocretin deficiency.
Other causes - idiopathic hypersomnolence and post traumatic brain injury
What is Cataplexy?
Sudden brief loss of voluntary muscle tone which can be triggered by strong emotions such as laughter.
One of the manifestations of narcolepsy
Explain narcolepsy with regards to the sleep cycle.
It tends to be due to a dysfunction of control of REM sleep
Patients go straight to REM sleep without going through NREM sleep so they become paralysed
What are the potential consequences of working night shifts?
Physiological processes could become desynchronised
This can lead to sleep disorders, fatigue and increased risk of some conditions such as obesity, diabetes and cancer
