Neuro 15: Consciousness + sleep Flashcards
What are the 5 behavioral criteria of sleep?
- stereotypic / species-specific posture
- minimal movement
- reduced responsiveness to external stimuli
- reversible with stimulation
- brain is still active when asleep
What are 3 methods of monitoring sleep?
- EEG
- EOG
- EMG
Describe patterns in awakefulness
AWAKE:
- fast brain rhythm in EEG (beta rhythm)
- up to 30 Hz
- reasonable amount of muscle tone
What happens in Stage 1 + 2 of sleep ?
- light sleep (Non Rem)
- person = becoming drowsy
- EEG activity = slowing
- gradually goes from BETA –> THETA
- 4-8 Hz
- no eye movements
- general muscle activity = reduced
What happens in stage 3 + 4 of sleep ?
- (Non-Rem)
- there is translation from THETA –> DELTA activity
- slowest rhythm at around 1Hz
- minimal eye movement at this point
- continued relaxation of muscles
- very deep sleep
What happens in stage 5 ?
- REM sleep
- brain activity shifts abruptly back to FAST rhythm
- rapid eye movements
- muscle activity = at slowest
Describe the sleep cycle
from beta activity –> rhythm gets slower + slower –> transition period –> REM sleep
1 sleep cycle lasts about :
90 minutes
Note: Earlier on in sleep there is more non-REM sleep
-
how does HR differ in slow wave sleep + REM sleep
Slow wave sleep: HR is slow
REM Sleep: HR faster
how does respiration rate differ in slow wave sleep + REM sleep
Slow wave sleep: resp rate is slow
REM Sleep: resp rate faster
What system controls consciousness?
- reticular activating system
Reticular activating system starts in:
Reticular activating system starts in: the brainstem
How does the reticular activating system influence the activity of the cerebral cortex?
a) directly
or
b) indirectly - via the intralaminar nuclei in the thalamus
note: higher activity of reticular activating system = higher level of arousal
What are the 2 nuclei in the hypothalamus that influences the RAS
- lateral hypothalamus
- -> promotes wakefulness
- ->excitatory input to RAS
- active during the day - Ventrolateral preoptic nucleus
- -> negative effect on RAS
- promotes sleep
What does the suprachiasmatic nucleus do?
it synchronizes sleep with falling light level
How does the suprachiasmatic nucleus synchronize sleep with falling light level ?
- it receives input from retina
- when light level falls –> suprachiasmatic nucleus becomes more ACTIVE
- and activates large no. of nuclei in the hypothalamus
- it INHIBITS the LH nucleus
- and STIMULATES the VLOP nucleus
and so at end of day you become more sleepy.
Suprachiasmatic nucleus has projection to the ____ _____
pineal gland
What happens when the suprachiasmatic nucleus activates the pineal gland at the end of the day?
- pineal gland will secrete higher level of melatonin
- which adjusts various physiological processes in the body that fit w sleep
- at end of the night: melatonin levels fall
What are some effects of sleep deprivation?
- sleepiness, irritability
- performance decrements
- concentration difficulties
- glucose intolerance
- hallucinations
What happens after sleep loss to regulate sleep?
- there is reduced latency to sleep onset
- -> so you go to bed earlier the next day - there is increase in slow wave sleep (NREM)
- -> you sleep for longer - there is an increase in REM Sleep
What are 3 main functions of sleep?
- restoration + recovery
- energy conservation
- predator avoidance
Most of dreaming occurs during NREM/ REM sleep
Most of dreaming occurs during REM sleep
What changes occur to brain activity when dreaming?
- activity of limbic system = higher than frontal lobe
What are 3 main functions of dreams?
- acts as safety valve for antisocial emotions
- disposal of unwanted memories
- memory consolidation
What are 2 main causes of chronic cases of insomnia?
- physiological e.g sleep apnea, chronic pain
- brain dysfunction e.g depression
How would you treat insomnia?
- try and remove cause / sleep hygiene
- use hypnotics
- -> which work by enhancing inhibitory (GABAergic circuits) circuits in the brain
What is narcolepsy?
- fallin asleep repeatedly throughout the day
with disturbed sleep during the night
What is cataplexy?
sudden onset of muscle weakness that may be precipitated by excitement / emotion
What might be the cause of narcolepsy?
–> often due to dysfunction of control of REM sleep
or due to orexin/hypocretin deficiency
How might night shift lead to sleep disorders?
- causes physiological processes to become desynchronized
Define consciousness
state of being aware of + responsive to one’s surroundings
What are 3 main disorders of consciousness?
- coma
- vegetative state
- minimally conscious state
What is meant by coma?
state of being unarousable/ unresponsiveness lasting more than 6 hours in which a person:
- can’t be awakened
- fails to respond normally to painful stimuli / light/ sound
- NO normal sleep-wake cycle
- does not initiate voluntary action
What is meant by vegetative state?
- state of wakefulness without awareness with preserved capacity for:
- spontaneous stimulus
- sleep-wake cycles
- and reflexive/spontaneous behaviors
- characterized by complete absence of behavioral evidence for self/ environmental awareness
(lights are on - but no one’s home)
What is meant by Minimally conscious state?
- state of severely altered consciousness
- where there is minimal but clearly discernible behavioral evidence of self/environmental awareness.
- characterized by inconsistent but reproducible response above level of spontaneous or reflexive behavior
- with some degree of interaction with surrounding
Which part of the brain is affected in vegetative state?
- there is destruction of cortex + hemisphere
Which part of the brain is affected in locked in syndrome?
- there is damage to ventral pons
Which part of the brain is affected in brain stem death?
- irreversible damage to brain stem
What type of test is used to monitor the level of arousal?
electroencephalography
What are some causes of coma?
a) hemisphere lesion
e. g cerebral infarct
- cerebral hemorrhage
- abscess
- tumor
b) brainstem
- brainstem infarct
- tumor
- abscess
- cerebellar hemorrhage
- cerebellar infarct
c) metabolic
- drug overdose
- hypoglycemia
- hypercalcaemia
d) diffuse injury
- meningitis
- head injury
- epilepsies
others: diffuse axonal injury, posterior fossa lesion
what is used to classify coma?
glasgow coma scale
score of 3 = serve brain injury + brain death
low GCS - think about protecting airway (<8)
how might you improve sleep? (sleep hygiene)
- establish fixed times for going to bed / waking up
- only go to bed when you are tired
- avoid caffeine
- avoid eating heavy meal at late night
- don’t use back-lit devices shortly before going to bed
What is meant by Hypersomnia
excessive daytime sleepiness
What are some Common cause of hypersomnia?
main cause: can't sleep at night - obstructive sleep apnea - restless elg syndrome - neurodegenerative diseases e.g parkinson - anxiety etc.
how would you quantify sleep in a test?
- epworth sleepiness scale
rating likelihood of dozing in various situations e.g whilst sitting + reading
What does reticular formation do?
involved in:
- cardiovascular control
- sleep and consciousness
- pain modulation
- in maintaining posture
note:
Brain activity = both integrated + differentiated.
e.g general seizures = highly integrated, but not differentiated
-
note: cognitive function = occurs through various network of brain regions
-
How is PCI used to quantify level of consciousness?
induce TMS –> measure rain activity with EEG afterwards a) if awake = pulse moves around brain
b) if asleep = signal doesn’t spread throughout brain
What is locked in syndrome?
When there is:
- no motor output
- but consciousness / awareness is normal
Arousal: Yes
Awareness: No
Vegetative state
Arousal: No
Awareness: No
Coma
Whats the difference between hemianopia and visual neglect
hemianopia - visual defect due to lesion to underlying pathway
visual neglect - higher order problem
- underlying pathway is intact
but perception is different (preference to one side)
Note: EEG lower frequency (e.g theta + delta)= usually bad higher frequency (e.g alpha) = usually more linked to cognitive function
alpha = good sign
- more prominent posteriorly, when eyes are closed/
What happens in Diffuse axonal injury
- patient would have higher order cognitive function defects
- e.g shown during a conversation
