Sleep - EEG features specifically in measurement and monitoring Flashcards
Define sleep
Sleep - a state of loss of reactivity to surroundings or unconsciousness which one can be aroused by sensory stimulation
What is non REM sleep
deep restful sleep and is the first state progressing from alert wakefulness with corresponding changes in EEG from low voltage, high frequency alpha waves to high voltage low frequency delta waves, with increasingly synchronous patterns. Raphe nucleus secretes seratonin modulating slow wave sleep
What area of the brain modulates slow wave sleep
Raphe nucleus
What neurochemical is heavily involved in slow wave sleep
Seratonin
What EEG featurs are generally seen in slow wave sleep
EEG from low voltage, high frequency alpha waves to high voltage low frequency delta waves, with increasingly synchronous patterns
What are the 4 stages of slow wave sleep
◦ Stage 1 - lightest stage and easiest to rouse - alpha waves interspersed with lower frequency theta waves (4-6Hz)
◦ Stage 2 - 50% of normal sleep - High frequency bursts (0.5 seconds) called sleep spindles 12-14Hz and classical large slow biphasic potentials called K complexes
◦ Stage 3 - Difficult to rouse - slow 1-2Hz, high voltage delta waves with occasional sleep spindles
◦ Stage 4 - large amplitude, rhythmic slow delta waves become synchronised
Describe stage 1 of slow wave sleep
◦ Stage 1 - lightest stage and easiest to rouse - alpha waves interspersed with lower frequency theta waves (4-6Hz)
Describe stage 2 of slow wave sleep
◦ Stage 2 - 50% of normal sleep - High frequency bursts (0.5 seconds) called sleep spindles 12-14Hz and classical large slow biphasic potentials called K complexes
◦
Describe stage 3 of slow wave sleep
Stage 3 - Difficult to rouse - slow 1-2Hz, high voltage delta waves with occasional sleep spindles
Descrieb stage 4 of slow wave sleep
◦ Stage 4 - large amplitude, rhythmic slow delta waves become synchronised
REM sleep is
paradoxical sleep difficult to wake from, preceeded by non REM sleep and REM is induced by noradrenaline from the locus coeruleus
Which neuronal centre is implicated in REM sleep
locus coeruleus
What neurochemical is associated with REM sleep
Noradrenaline
What is the pattern of slow wave to REM sleep
◦ About every 90 minutes sleep lightens, heart rate and respiratory rate increase, muscle tone returns and followed by brief period of profound relaxation associated wtih rapid eye movement, and desynchronised low voltage (low amplitude), high frequency EEG +large physic waves called ponto-geniculo-occipital spikes from the pons to geniculate and Occitan regions lasting 15 minutes
In the absence of EEG what might be some clues as to REM sleep occuring
◦ About every 90 minutes sleep lightens, heart rate and respiratory rate increase, muscle tone returns and followed by brief period of profound relaxation associated wtih rapid eye movement, and desynchronised low voltage (low amplitude), high frequency EEG +large physic waves called ponto-geniculo-occipital spikes from the pons to geniculate and Occitan regions lasting 15 minutes
What EEG features help distinguish REM sleep
Desynchronised low voltage (low amplitude), high frequency EEG +large physic waves called ponto-geniculo-occipital spikes from the pons to geniculate and Occitan regions lasting 15 minutes
What two phases are there to REM sleep and how do they physically appear different
◦ REM sleep divided into phasic and tonic phases
‣ Phasic - motor activity e.g. rapid eye movements, autonomic instability and dreaming
‣ Tonic - tonic inhibition of muscle tone
What happens respiratory wise in non REM sleep
◦ Respiratory rate decreased and regular respiration —> decreased minute volume
‣ 25% reduction in minute alveolar ventilation
‣ Increased PaCO2 slightly, and reduced PaO2
◦ Reduce upper airway muscle tone - pharyngeal dilator tone reduced particularly in stage 3 non REM sleep
‣ 2x increase in airway resistance
◦ Hypoxic drive and CO2 response diminished —>mild hypercarbia and hypoxaemia
What happens in REM sleep to the respiratory system
- REM sleep
◦ Respiratory drive further reduced + occasionally irregular leading to further minute volume and alveolar ventilation reduction
◦ Increased PaCO2 and reduced PaO2 with further blunting to hyper apnoeic and hypoxic regulatory responses
◦ Further loss of skeletal thoracic cage muscle tone and upper airway —> paradoxical breathing and upper airway obstruction
What is consciousness
State of beign aware and responsive to ones surroundings
What is the reticular formation
Diffuse aggreagtion of cells with a network of fibres that run in all directions in the core of the brainstem (medulla nad pons) concerned with somatic muscle control, regulation fo eye, neck, trunk and limb movements and may also received somatic, proprioceptive sensory signals as well as descneding inputs from the cerebral cortex and limbic system
What two parts of the reticular activiting system are there anatomically - where does each project
Pontine - projects psilaterally down the spinal cord –> antigravity reflexes, automatic maintenance of erect posture
Medullary - axons down both sides of the spinla cord, suppresses spinal reflexes during sleep and may override spinal influences in voluntary movement via descending pathways
Where do reticular activating descending impulses terminate
ventromedial group of interneurons
What is a locus coeruleus
group of neurons containing norepinephrine as a NT in the pontine reticular formation
What are the raphe nuclei
midline pons nuclei, send axons to excite or inhibit the thalamus
Why is the reticular activating system important
modulates the pacemakers in the thalamus, influencing cortical neuronal excitabuility
What is the gradual wave in brain wave pattern as you progress through the phases of sleep
shift from low voltage high frequency alpha waves to low frequency, high voltage delta waves - progression to synchronous rather than desynchronised activity
How often does REM sleep occur
90 minutely
How long does REM sleep typically last
15 minutes
What effect does REM sleep have on depth of sleep, heart rate and RR
Sleep lightens, HR and RR increase and muscle tone briefly returns before profound relaxation of skeletal muscle and rapid eye movements
Is REM a deep sleep or light?
Deep
Paradoxically the EEG is similar to someone in a shalllow sleep
Physiological changes during REM sleep
Dreaming
Muscle done makredly decreased - snoring and airway obstruction more likely
HR and RR irregular
BP decreased durng tonic phase, but may increase during the phasic phase
Unusual muscle contractions and bruxism in the phasic phase
Brain metabolism increased by as much as 20%
Glucocorticoid production increased
Cerebral blood flow increases
Where does the circadian rhythm come from
Suprachiasmatic nucleus of the hypothalamus receiving input from the retina, and melatonin released from the pineal gland
Slow wave sleep neurotransmitter
serotonin from the raphe nucleus
REM sleep neurotransmitter
Locus coeruleus releasing NA
REM sleep EEG changes
Rapid, low voltage and irregular (desynchronised) EEG
lrge phasic waves called pontogeniculooccopital (PGO) spikes from the pons to the geniculate body and occipital cortex
What percentage of sleep is REM
15%
Two phases of REM sleep
Tonic - tonic inhibition of muscles
Phasic - Rapid eye movement, autonomic instabilit with irregular respiration and dreaming
Muscle tone during sleep
Reduced in NREM and REM sleep - tonic inhibition in REM profound, phasic muscle contractions. Tone of upper airways reduced
Respiratory changes in sleep
NREM
- RR decreased and regular
- 25% decrease in alveolar ventilation
- Rise in PCO2 by 3-7mmHg
- Decreased in PaO2
- Increase in airway resistance x 2
- Reduced muscle tone of upper airway partly to blame
- HYpoxic drive and CO2 response diminished in the medullar
REM
- Irregular breathing
- Paradoxical breathing and upper airway obstruction can occur with reduced tone
- total body oxygen consumption is higher in REM than in NREM but still less than wakefullness
Airway reflexes decreased
Coughing impossible
Laryngeal stimulation produces apnoea
Mucociliary clearance reduced
Cardiovascular changes in sleep
BP decreased during NREM and tonic REM; can increase in phasic RE. It is at its lowest in stage 3 and 4 of NREM sleep
Cardiac output decreased in all phases of sleep
HR and SVR decreased in NREM and tonic REM but icnreased in phasic REM
Pulmonary vascular resisatnce increased
Blood flow redistributed from the skin and muscles to splanchnic organs
Transient vasoconstriction events occur during sleep - death from cardiac disorders most frequently occurs durnig sleep between 5-6am
central inhibition of the baroreflex
CNS effects of sleep
Cerebral oxygen consumption reduced in NREM sleep. increased above resting values in REM
Cerebral blood flow normal in NREM but increases by 50% in REM sleep
Increased PSNS and decreased SNS in all parts of sleep except phasic
ICP increased during REM but no NREM
Endocrine effects of sleep
Meltatonin from the pineal gland released due to darkness
Growth hormone increased at the onset of sleep, highest during slow wave sleep. All pituitary hormones except ACTH are increased during sleep, as well as vasopressin and aldosterone increases.
Cortisol decreased during the onset of sleep, and trough in earlty hours of the morning and incrteases during the second half of sleep with peak just after waking
Later part of sleep insulin and glucose fall despite continous glucose
Metabolic rate decreased by 15%
Effect of sleep on temperature regulation
Body core temperature decreases by 0.5 degreees and shivering threshold decreased
What is the limbic system composed of
Subcortical - hypothalamus, septum, hippocampus, amygdala
Limbic cortex - cingulated gyrus, orbitofrontal cortex, subcallosal gyrus and parahippocampal gyrus
What inputs does the limbic system have
association cortex, olfactory cortex and medial temporal obe
Functions of the limbic system
Hippocampus - memory acquisition and recall, formation fo long term memory and behaviour
Amygdala - emotional processing of stimuli, fear, rage and anxiety
Septal nuclei - pleasure and reward
Cingulate gyrs - affective aspects of events
Draw the processing of the limbic system
Effect of sleep on GIT
Secretion of saliva slows, swallowign is impossible
oesophageal motility decreeased
Increased splanchnic blood flow
Describe the relative times in each sleep stage and the typical pattern of sleep over a night
Describe the effect of sleep on relative blod flow
What is K complex in the context of EEG sleep
N2 stage:
Spindles (burst-like trains of waves in the 11- to 16-Hz range with a total duration ≥0.5 seconds)
K-complexes (well-defined biphasic waves lasting ≥0.5 seconds and usually maximal over the frontal cortex)
What is a spindle in the context of EEG and sleep
N2 stage:
Spindles (burst-like trains of waves in the 11- to 16-Hz range with a total duration ≥0.5 seconds)
K-complexes (well-defined biphasic waves lasting ≥0.5 seconds and usually maximal over the frontal cortex)
Renal effects of sleep
UO decreases
urinary excretion of electrolytes decreases
Where does the inhibition come from that mediates sleep
Hypothalamic GABA eergic inhibition fo arousal pathways
How does sleep and sedation compare
critically ill sedated patient, demonstrating that the majority of the time is maintained in N1 sleep, with microarousals every ten seconds. That doesn’t sound restful. N1 stage sleep is the earliest and most shallow stage; if a person is woken from N1 stage sleep they frequently will not be able to identify the fact that they went to sleep at all.
What is sleep
a state of loss of reactivity to surroundings or unconsciousness which one can be aroused by sensory stimulation
Slow wave sleep is
deep restful sleep and is the first state progressing from alert wakefulness with corresponding changes in EEG
Describe the EEG progression from awake to asleep
from low voltage, high frequency alpha waves to high voltage low frequency delta waves, with increasingly synchronous patterns
Stage 1 of sleep - characteritsics? EEG features
◦ Stage 1 - lightest stage and easiest to rouse - alpha waves interspersed with lower frequency theta waves (4-6Hz)
Stage 2 sleep characteristied by? What % of normal sleep? Classic findings? 2
◦ Stage 2 - 50% of normal sleep - High frequency bursts (0.5 seconds) called sleep spindles 12-14Hz and classical large slow biphasic potentials called K complexes
Stage 3 sleep EEG features
◦ Stage 3 - Difficult to rouse - slow 1-2Hz, high voltage delta waves with occasional sleep spindles
Stage 4 sleep? EEG features
◦ Stage 4 - large amplitude, rhythmic slow delta waves become synchronised
EEG orders of wakefulness
Gamma
Beta
Alpha
Theta
Delta
REM sleep - easy to wake? Induced by?
paradoxical sleep difficult to wake from, preceeded by non REM sleep and REM is induced by noradrenaline from the locus coeruleus
What indicates REM sleep has started to an observer?
Sleep lightens, HR and RR increase, muscle tone returns briefly followed by profound relaxation and desynchronised low voltake high frequency EEG with ponto-genicuo-occipital spikes
What is the characteritsic EEG finding to REM sleep
EEG with ponto-genicuo-occipital spikes
How often does REM occur
90 minutely
REM sleep phases? What charactertises each
◦ REM sleep divided into phasic and tonic phases
‣ Phasic - motor activity e.g. rapid eye movements, autonomic instability and dreaming
‣ Tonic - tonic inhibition of muscle tone
Non REM sleep effect on respiratory status
Decreased MV due to reduction in RR
25% reduction in alveolar ventilation
Increased PaCO2, and reduced PaO2
Reduced upper airwy tone and pharyngeal dilator tone, esp phase 3. 2x increase in wairway resistance
Hypoxic drive and CO23 response blunted
REM sleep effects respiratory drive how
◦ Respiratory drive further reduced + occasionally irregular leading to further minute volume and alveolar ventilation reduction
What effect does REM have on gas exchange?
◦ Increased PaCO2 and reduced PaO2 with further blunting to hyper apnoeic and hypoxic regulatory responses
Is upper airway obstruction more likely to occur in REM or non REM
REM - especially the tonic phase
