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
Draw the processing of the limbic system
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
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.
