Sleep, EEG Flashcards
Define sleep
Easily reversible state of inactivity with a lack of interaction with the environment
What is consciousness?
Having awareness, with perceptions, thoughts and feelings
What are the two main forms of externally discernible sleep?
- When the eyes move rapidly side to side (REM)
* When they do not (non-REM/ slow wave/ deep sleep)
How does the EEG work?
- Picks up post synaptic activity of synchronised dendritic activity
- The more neurones that are synchronised, the bigger the peaks on the EEG
Describe stage 1 of sleep
- Stage 1: duration of 1-5 minutes, easily aroused, slow rolling eye movements
- Some theta waves and higher amplitude waves
Describe stage 2 of sleep
- 10-15 minutes
- K complexes
- Sleep spindles
- No eye movement
- Body movement remains possible
Describe stage 3 of sleep
- Few mins duration
- Slower frequency
- Delta waves appear
- harder to rouse
- Few spindles
Describe stage 4 of sleep
- Deepest sleep
- Hardest to rouse
- EEG waves at 2Hz and high amplitude - delta waves
- Lower heart rate and BP
- 15-30 minutes
Describe REM sleep
- Fast beta waves
- Rapid eye movement
- Subject easier to rouse than in stage 4
- Dreaming recalled
- Low muscle tone
Typical night sleep
- Several cycles through the 5 stages of sleep
- Stage 4 is only reached in the initial cycles
- deepest sleep attained after is stage 3
What is REM characterised by?
- Rapid eye movement
- Increases in heart rate
- Increased neuronal activity
- Increased respiration and oxygen consumption
- Penile erection
What is the reticular formation?
• Diffuse collection of at least 100 networks of neuromodulatory neurones spanning all three divisions of the brainstem
Where do the projections of the reticular formation go to?
- Thalamus
- Hypothalamus
- Some brainstem nuclei
- The cerebellum
- Spinal cord
- Cerebral cortex
Where does the reticular formation receive input from ?
- The cerebra (collaterals from the corticospinal pathway)
- visual and auditory systems
- Sensory spinal system
- Cerebellum
- Certain brainstem nuclei
Describe the neural control of non-REM sleep
- Cortical slow waves caused by hyper polarised thalamus
- Decreased activity in the arousal centres of the reticulum
- Sleep spindles and L complexes are caused in part when the thalamic neurones hyperpolarise (due to reduced ascending reticular formation input)
- Slow wave rhythmicity blocks ascending sensory input
Where are orexinergic neurones
In the lateral hypothalamus, they project to the cerebra, arousla nuclei, vneterolateral pre optic nuclei in the anterior hypothalamus
VLPO lesion
insomnia
What is the effect of orexin?
Enhance the arousal nuclei and cause indirect inhibition of the VLPO via reciprocal inhibition pathways
What is the centre of non REM sleep?
Ventrolateral pre-optic nucleus
What is the role of the suprachiastmatic nucleus?
- Controls circadian cycle s
* Influences physiological and behavioural rhythms occurring over a 24 hour period including the sleep/wake cycle
What resets the clock gene?
Receptors in the retina containing melanopsin react to light and synapse directly onto the SCN
What causes narcolepsy?
- Onset due to specific loss of the orexin containing neurones in the lateral hypothalamus
- Thought to be an inherited auto-immune condition linked to chromosome 6
How does narcolepsy present?
- Repeatedly falling asleep during the day, regardless of current activity - go straight to REM sleep
- Limb weakness during emotional episodes
- Night time or morning wakening accompanied by muscular paralysis
- Vivid dream recollection just prior to wakening
Wha tis the treatment of narcolepsy?
- Modafanil
- Amphetamines
- Methylphenidate
- Sodium oxybate
- SSRIs and tricyclic antidepressants suppress REM sleep
- Venlafaxine may help cataplexy
Simple partial seizure
- Focal with minimal spread of abnormal discharge
* Normal consciousness and awareness maintained
Complex partial seizure
- Local onset then spreads
- Impaired consciousness
- Clinical manifestation varies with site of origin and degree of spread
- Temporal lobe epilepsy most common
Secondarily generalised seizures
- Begins focally, with or without focal neurological symptoms
- Variable symmetry, intensity and duration of tonic (stiffening) and clonic (jerking) phases
- Typical duration up to 1-2 minutes
- Postictal confusion and somnolence
Generalised seizures
- Noth hemispheres
- present in 40% of all epileptic syndromes
- Manifestation of the seizure determine by cortical site at which the seizure arises
What are the generalised seizures?
- Absence
- Myoclonic
- Clonic
- Tonic
- Tonic-clonic
- Atonic
Absence seizure
- Petit-mal
- Sudden onset and abrupt cessation
- Consciousness is altered
- Mild clonic jerking, postural tone changes, autonomic phenomena
atonic seizure
- sudden loss of postural tone
* Most often in children
Tonic-clonic seizure
- Grand mal
- Major convulsions with rigidity (tonic) and jerking (clonic)
- Slows over 60-120 seconds followed by stuporous state
Which seizures are non-convulsive?
Atonic and absence
What is status epilepticus?
- More than 30 minutes of continuous seizure activity
- Two or more sequential seizures spanning this period without full recovery between seizures
- Medical emergency
What are the targets for AEDs?
- Increase inhibitory neurotransmitter system - GABA
- Decreased excitatory neurotransmitter system
- Block voltage gated inward positive currents
- Increase outward positive current
- Many AEDs pleiotropic - act via multiple mechanisms
