Neurophysiology Flashcards
Sleep measurements
Actigraphy: quantifies circadian patterns and movement disorders. Motion sensor.
Polysomnography: EEG, EMG, EOG. Oximetry and respiratory monitor can be added. Looks at sleep latency, REM latency ~ 90 mins. Non-REM latency, Sleep efficiency (total sleep time/total time in bed) x 100.
Multiple sleep latency test: daytime somnolence and daytime REM onset.
Resting membrane potential
Action potential initiated when -70 to -55mV > Na channel influx > causes rapid reversal of me brake potential from -90 to +40 mV > Na channels close and K channels open > depolarises the membrane
Sleep cycle
Rem and non rem (75%)
Non REM: Increased parasympathetic activity. Abolition of tendon reflexes. Upward ocular movements.
REM: high activity, theta and slow alpha waves, saw tooth waves. Eye movement dart. Penile erection/vaginal blood flow, Increased recall of dream. Increased sympathetic activity. Occasional myoclonus jerks. Increased protein synthetis. Conjugate ocular movements. Maximal loss muscle tone.
Stage 1: very light, drowsy, 5% of sleep time.
Theta, V sharp waves.
Stage 2: sleep spindles and K complexes. 45% of sleep.
Stage 3: < 50% delta waves, 12% of sleep time.
Stage 4: > 50%’delta waves, 13% of sleep time. Physiological functions at the lowest.
Stage 3+4 = SWS.
Sleep spindles
Stage 2
Upper levels of Alpha or lower levels beta.
< 1 second
Symmetric
Parasagittal region
K complex
Large amplitude delta waves
Throughout brain, more so BIFRONTAL.
Usually symmetric
Occur when aroused partially from sleep
If followed by rhythmic theta waves = “arousal burst”
V Waves
Sharp waves.
During sleep.
Largest.
Most at vertex bilaterally and usually symmetrical.
Stage 2’sleep.
Often occur after sleep disturbances/semi arousal
Sleep
Newborns sleep 16 hrs, > 50% REM
By 4 months, REM < 40%
By late teens, adult sleep.
Old age: reduction in SWS and REM and increase awaking After sleep onset.
Dreams thought like in non-rem, and bizarre illogical in rem.
Sleep regulation
Master clock = suprachiasmatic nucleus in anterior hypothalamus
Retinal ganglion cels project via retina hypothalamic tract to SCN, to provide light input independent of vision. SCN resets daily by light signals from retina/melatonin.
Without solar guidance, sleep wake cycle would increase to 26 hours “free running”
VLPO induced sleep, projects to the ascending arousal system. Dosage to Vlpo causes chronic insomnia. Switching from sleep to awake, is stabilised by OREXIN NEURONS “HYPOCRETIN” in hypothalamus. Narcolepsy has few HYPOCRETIN Neurons,
Sleep and disorders
Alcohol increases sws, reduced initial rem but increases second half of rem.
Alcohol withdrawal: loss of sws, increased rem and rem rebound
Anxiety: increased stage 1 sleep, reduces rem and sws, normal rem latency.
Bzd: decreases sleep latency, increases sleep time, reduce stage 1/rem/sws sleep, increases stage 2 sleep. On cessation get rem rebound.
Cannabis: increases sws, suppresses rem
Cbz: as cannabis, also increase rem latency
Dementia: increase latency, reduced sleep time, fragmented sleep
Depression: loss first half sws, increased rem therefore emw, reduced rem latency
Lithium: suppresses rem, increases rem latency, increases sws
Opiates: decreases sws and rem, withdrawal causes rem rebound
Schizophrenia: reduction rem latency and sws. Inconsistent however.
SSRI: alerting (5HT2 stimulation), ?reduce rem latency.
Stimulants: reduces sleep time, decreases rem sleep/sws.
TCA: Suppresses rem. Increases sws and stage 1.
Z drugs: less effect on sleep architecture, zopiclone may increase sws.
EEG
Psychotropics: Slow Beta waves, Lithium slows Alpha, no change for anticonvulsants on EEG.
Sedating drugs: Barbiturates & BZD decrease alpha and increase beta, Opioids decrease alpha increase theta and delta.
Recreational drugs: INCREASE ALPHA. Alcohol increases alpha and theta > DT causes Beta fast wave activity. Caffeine withdrawal produces increase theta activity.
Rem sleep
Reduced muscle tone
Rapid low voltage EEG > SAWTOOTH PATTERN
Sleep onset to REM sleep is around 90 minutes
EEG infant
3 Hz
In newborns and new toes dominant is delta and theta activity
REM BEHAVIOURAL DISORDER
Normally REM sleep is associated with loss of muscle tone and dreaming.
In RBD, there is no loss of muscle tone and the dreams are acted as complex behaviours. Patients act out their dreams, with limited awareness of surroundings. The episodes arise during the middle to latter third of the night during REM sleep. It may occur idiopathically.
Associated with disorders such as Parkinson’s disease, diffuse Lewy body disease, multiple system atrophy and Gullian–Barré syndrome. RBD may be the prodrome of neurodegenerative disease, such as DLB or Parkinson disease.
It can precede the diagnosis of a movement disorder by several years.
It is likely that the associated lesions are situated in the brainstem.
Treatment with clonazepam has been shown to be effective
EEG DISORDERS
Alzheimer’s: reduced ALPHA. Rarely normal in advanced dementia.
Partial seizures: localised spike or spike-wave discharges.
Schizophrenia: nil characteristic
Psychopathy: immature temporal posterior slow waves
Delirium: increase DELTA and some alpha waves
Neurosyphilis: increase in slow waves diffusers over scalp
Stroke: focal/regional Delta
Chemical Transmitters (to do with food!)
Neuropeptide Y secreted by hypothalamus. Increases food intake and decreases active, increases proportion of energy stored as fat.
Ghrelin: produced by stomach, stimulates hunger.
Leptin: protein hormone produced in adipose tissue, regulates energy intake and expenditure, including appetite and metabolism. Internal measure of energy state.
