Sleep Flashcards
what are the behavioural criteria for sleep?
- posture (species specific)
- minimal movement
- reduced responsiveness to stimuli
- reversible via stimuli unlike with coma
what are the 3 main methods of monitoring sleep?
EEG
EMG
EOG (Electrooculogram)
muscle tone and brain activity whilst awake
fast brain activity in EEG (beta rhythmn displayed at 30Hz)
some muscle tone
changes in brain activity and muscle movement in light sleep (stages 1 and 2)
beta become theta rhythmn (4-8Hz)
EEG activity slows down
no eye movements
general muscle activity reduced
changes in brain activity and muscle movement in deep sleep (stages 3 and 4)
theta becomes delta activity (slowest rhythmn at 1 Hz)
minimal eye movement
continued relaxation of the muscles
stage 5 sleep
REM Sleep
brain activity becomes fast
REM is visible
lowest muscle activity (paralysed)
which stages of sleep are non-REM?
1-4
how long does a sleep cycle in the night last?
1-1.5 hours
when is REM sleep more frequent?
towards the end of the night
more slow-wave sleep at the beginning
heart rate and respiration rate during the night
at the beginning with slow wave sleep, heart rate and resp rate are slower and they get faster with REM sleep
what system controls conciousness and where does it project into and influence?
Reticular activating system
starts in the brainstem and projects into the cerebral cortex to exert its influence
types of effects of the RAS
direct or via the intralaminar nuclei
which part of the hypothamalus exerts the excitatory input of the RAS?
lateral hypothalamus (active during the day)
what part of the hypothalamus exerts the negative effect of the RAS?
ventrolateral preoptic nucleus
promoting sleep
relationship between lateral hypothalamus and ventrolateral preoptic nucleus?
antagonistic
the activity of one inhibits the other
regulated by the suprachiasmatic nucleus
which nucleus synchronises sleep with falling light level
Suprachiasmatic nucleus (SCN)
how does the SCN reduce traffic in the RAS and therefore induce sleep
- light input is received via the retina
- light falls on a non-RGC ganglionic cell
- the falling level of light activates the SCN more
- causing an inhibition of the LH and increased activity of the VPN which can have its negating effect on RAS whilst reducing RAS traffic
MORE light–> LESS SCN activity
SCN is a sleep inducer
what are the effects of sleep deprivation?
o Sleepiness and irritability.
o Performance decrements/increased risk of error.
o Concentration and learning difficulties.
o Glucose intolerance.
o Reduced leptin – increased appetite
o Hallucinations- after long deprivation
o Death- fatal familial insomnia
what are the reactive effects as a result of sleep loss?
- reduced latency to sleep onset (sleep earlier the next day)
- increased NREM i.e. more slow-wave sleep as you sleep longer
- increased REM after REM sleep deprivation
function of sleep
- restoration and recovery
- energy conservation ( 10% BMR decrease is also achieved by lying still)
- [predator avoidance]
- brain functions
- memory
which part of sleep is REM sleep most common?
in REM sleep but can occur in NREM
dreams in REM is more easily recalled
characteristics of dreams
more emotional than real life
this is due to higher limbic system activity than frontal lobe during dreams
limbic system involves emotion regulation while the frontal lobe involves logical thought and informed decision making
functions of dreams
- safety valve for antisocial emotions
- sorting memories, removing irrelavant information
- memory consolidation
memory consolidation in NREM and REM
NREM- declarative memory - facts and events
REM- procedural memory- learning skills
two main causes of insomnia
1) physiological
- sleep apnoea
- chronic pain
2) brain dysfunction
- depression
- FFI
- night work
treating insomnia
removing the cause
hypnotics enhancing the GABAergic circuits (inhibitory effects)
improve sleep hygiene
sleep CBT
what is narcolepsy?
falling asleep repeatedly during the day with distrubed sleep in the night
what is cataplexy?
sudden onset muscle weakness precipated by strong emotion like excitement.
can cause the person to fall over
causes of narcolepsy
orexin/hypocretin deficiency
(orexin is a neuropeptide used as the transmitter by the lateral hypothalamus)
can be genetic or autoimmune
person needs to adhere to strict sleeping routines
what are the effects of night shifts
physiological processes become desynchronised
sleep disorders, fatigue
increased risk of diabetes, obesity and cancer
