Sleep, Wakefullness and the ECG Flashcards
What are the three states of consciousness
wakefullness
core consciousnes- wakefullness plus emotional responses, simple memory
extended consciousness- all of the above plus self awareness, autobiographical memory, language and creativity
are brain neurones active during sleep
yes but have a different activity
what are the two main phases of sleep
REM and non REM/ slow wave or deep sleep
what signals can be picked up from the EEG
post synaptic activity of synchronised dendritic activity but not individual neurons
what determines the size of the peak on the EEG
the number of neurons that are synchronised
what causes neurons to synchronise
neuronal interconnections or by pacemaker
describe how EEGs are performed
electrodes are arranged in 19 pairs on the surface of the head
comparison between pairs of electrodes provides a pictures of neuronal activity in areas of the brain
what happens during stage one sleep
slow rolling eye movements, theta waves
what happens during stage 2
K complexes and sleep spindles, no eye movements, body movement remains possible
what happens during stage 3 sleep
slow frewuency delta waves
harder to rouse
what happens in stage 4 sleep
deepest sleep hardest to rouse
heart rate and blood pressure lower
synchronised firing of large groups of neurons
what happens in REM sleep
fast beta waves and REM, easier to rouse than in stage 4
dreaming and low muscle tone
how long does it take to get from drowsy to deep sleep
one hour
describe sleep cycles throughout the night
stage 4 is only reached in the initial cycles, thereafter the deepest sleep atained is stage 3
what are the characteristics of REM sleep
increase in heart rate, neural activity, respiration and oxygen consumption, erection
what are the subtypes of alpha waves
visual cortex (classic)
sensory motor cortex (mu)
auditory( kappa)
what is the function of slow waves
thought to be involved with inhibiting sections of the relevant cortex
during what stage of sleep is the body paralysed, and body temperature drops
REM
what is the reticular formation
a diffuse collection of at least 100 neuromodulatory neurones spanning all three divisions of the brainstem
pathways in the brainstem connecting the spinal cord, cerebrum, and cerebellum, and mediating the overall level of consciousness.
it is not homogenous and has diverse functions
what are the functions of the reticular formation
posture, respiration, sleep, heart rate
where does the reticular formation project to
the thalamus, hypothalamus, brainstem nuclei, cerebellum, spinal cord and cerebral cortex
what does the reticular formation recieve input from
cerebra, visual and auditory systems, sensory spinal systems, cerebellum, certain brainstem nuclei
what structure is required for consciousness
release of neurotransmitters from neurones of the reticular formation (norepinephrin, serotonin, acetylcholine)
what neurotransmitters are required for consciousness
norepinephrin, serotonin, acetylcholine
what structure modulates arousal in the cerebral cortex
thalamus
what inputs go to the thalamus
midbrain reticular formation vestibulocochlear nuclei spinal nucleus 5 spinoreticular pathway nucleus basalis thalamus
how can excitability of the thalamus be controlled
reticular formation
what is the effect of lesions to the thalamus on the eeg
most synchronous eeg waves are abolished
what stimulates stage 4 sleep
rhythmic stimulation of the thalamus induces stage 4 sleep
how can EEG wave types can be changed
activation of the reticular formation and so the thalamus- increasing stimulation of the thalamus increases alertness
what 3 structures are most concerned with wakefulness and are interconnected
thalamus, reticular formation, cerebral cortex
describe the effect of excitation on the reticular formation
depolarisation of the thalamus causes non rhythmic output to the cortex
this causes increase arousal (alpha and beta waves)
describe the effect of inhibition to the reticular formation
this causes hyperpolarisation of the thalamus which causes rhythmic output to the cortex
this causes slow EEG waves in the cerebral cortex so deeper sleep
how is deeper sleep achieved
inhibition of the reticular formation
what is non rem sleep characterised by
slow synchronised cortex waves, caused by a hyperpolarised thalamus and decreased activity in the arousal centres of the reticulum
what causes sleep spindles and K complexes (stage 2)
inherent rhythmicity of thalamic neurons as they hyperpolarise due to reduced ascending reticular formation input
describe the effect as thalamic cells hyperpolarise further
they develop slow wave rhythmicty due to thalamic interconnections which blocks ascending sensory input this rhythmicity is transmitted to the cortex and the waves become synchronised
what does the locus coeruleus block during rem sleep
descending motor output
describe the oxygen consumption of the brain during rem sleep
uses more than awake and engaged in a complex problem
what does the midbrain reticular formation do during rem
excites the thalamus and provides descending inhibitory stimuli to the motor pathways
describe the passage from wakefullness to sleep
midbrain reticulum projects cholinergic excitation onto the thalamus
pathway is on except for NREM sleep
direct cortical excitation is quiescent during REM sleep (lesions cause coma)
what is the ventrolateral pre optic nuceus
the centre of NREM sleep promotion
it has inhibitory projections to all the major arousal centres and is active during sleep
what structures inhibit the ventrolateral pre optic nucleus
arousal centres
what are orexinergic neurons
normally acitve during wakefullness (lateral hypothalamus)
they project to the cerebra, the arousal nuclei and the VLPO
this causes indirect inhibition of the VLPO via reciprocal inhibition pathways
what hormone is pivotal in sleep awake switch circuitry
orexin
what happens when orexin is released
stimulates arousal centres and so causes inhibition of the VPLO
shifts the balance towards wakefulness
what happens when the VPLO fires
inhibits orexinergic neurons and the arousal centres
this causes sleep
where is the suprachiasmatic nucleus located
hypothalamus
what does the suprachiasmitic nucleus control
circadian cycles, physiolical and behavioural rhythms including sleep wake cycle
what resets the SCN clock
zeitgebers (time givers) e.g. the light/ dark cycle
what do receptors in the retina contain
melanopsin which reacts to light and resets the clock gene
what are the two forms of permanent insomnia
rare inherited neurodegenerative process affecting the thalamus and the rostral hypogenic sleep centres
stroke resulting in blockade of the basilar artery causing locked in sydrome, if this includes the loss of the pontine hypogenic centre the result can include insomnia
what causes narcolepsy
loss of orexinergic neurons in the lateral hypothalamus
inherited autoimmune
what are the symptoms of narcolepsy
repeatedly falling asleep during the day
limb weakness during emotional episodes (cataplexy)
night time or morning wakening accompanied by muscular paralysis
vivid dream recollection
caused by pontine influence of muscle tone during REM
What is the term for sleep walking
somnambulance
what is REM sleep behaviour disorder
n the descending pontine reticular
formation fails to properly immobilise the body. Characterised
by rapid/violent movement and behaviour
what is somnambulance
during non-REM sleep. Often the
same as REM sleep behaviour disorder but there is no memory
of the dreams enacted. Occurs in NREM sleep which is why
there is no memory, and happens when the midbrain reticular
formation fails to paralyse the body
