Sleep & Consciousness Flashcards
4 BEHAVIOURAL CRITERIA for sleep:
- Stereotypic or species-specific posture (i.e. humans sleep lying down typically)
- Minimal movement
- Reduced responsiveness to external stimuli
- Reversible with stimulation- unlike coma, anaesthesia or death
What are the three things that are usually measured when monitoring sleep
Eye movement (EOG) Muscle activity (EMG) Brain activity (EEG)
What happens to eye movement, muscle activity and brain activity in stages 1 and 2 of sleep?
The person is becoming more and more drowsy and the EEG activity is slowing
There are NO eye movements
The general muscle activity has been reduced considerably
Gradually you go from beta activity to theta activity (4-‐8 Hz)
What happens to eye movement, muscle activity and brain activity in stages 2 and 4 of sleep?
There is minimal eye movement at this point
There is continued relaxation of the muscles
This is very deep sleep
Lowest frequency delta activity of brain waves
What happens to eye movement, muscle activity and brain activity in stage 5 of sleep?
Brain activity shifts abruptly back to fast rhythm
This is quite similar to the activity you see in awake subjects
You get rapid eye movement even though the subject is asleep
The muscle activity is at its lowest so the person is basically paralysed
Which stage is REM sleep
5
How long is a cycle of the 5 stages of sleep
90 mins
Effect on HR and resp rate in REM sleep?
increase
Activity of the brain sequence in greek symbol terms
Awake = beta -> theta -> delta
Consciousness is mainly controlled by What
RETICULAR ACTIVATING SYSTEM
RETICULAR ACTIVATING SYSTEM does what
controls consciousness
LATERAL HYPOTHALAMUS does what
promotes wakefulness (orexin (or hypocretin) system- this promotes wakefulness)
VENTROLATERAL PREOPTIC NUCLEUS does what and where is it
in the anterior hypothalamus) promotes sleep
SUPRACHIASMATIC nucleus does what
synchronises sleep with falling light level
What part of the brain synchronises sleep with falling light level
SUPRACHIASMATIC NUCLEUS
What part of the brain (in the anterior hypothalamus) promotes sleep
VENTROLATERAL PREOPTIC NUCLEUS
What part of the brain promotes wakefulness (through orexin (or hypocretin) system- this promotes wakefulness)
LATERAL HYPOTHALAMUS
Where is the VENTROLATERAL PREOPTIC NUCLEUS found
Hypothalamus
Psychiatric and neurological EFFECTS OF SLEEP DEPRIVATION? (7)
- Sleepiness, irritability, stress, mood fluctuations, depression, impulsivity, hallucinations
neurological EFFECTS OF SLEEP DEPRIVATION? (3)
- Impaired attention, memory, executive function
- Risk of errors and accidents
- Neurodegeneration
Somatic EFFECTS OF SLEEP DEPRIVATION? (5)
- Glucose intolerance
- Reduced leptin/increased appetite
- Impaired immunity
- Increased risk of CVD and cancer
- Death
how is sleep REGULATED ACCURATELY? (After sleep loss…)
- Reduced latency to sleep onset (easier to get to sleep again)
- Increase of slow wave sleep (NREM)
- Increase of REM sleep (after selective REM sleep deprivation
Functions of sleep? (4)
Restoration and recovery But active individuals do not sleep more
Energy conservation 10% drop in basal metabolic rate- but lying still is just as effective
Predator avoidance But then why is sleep so complex
Specific brain functions Memory consolidation etc.
Dreams occur more frequently in what stage of sleep
5
Dreams are more easily recalled in what stage of sleep
- More easily recalled in REM sleep
Which part has a higher brain activity during dreams, limbic or frontal lobe
Limbic
Function of dreams? (3)
- Memory consolidation
- Disposal of unwanted memories
- Release of antisocial emotions
causes of chronic cases of insomnia? (5)
- Physiological e.g. sleep apnoea, chronic pain
- Brain dysfunction e.g. depression, fatal familial insomnia (a prion disease), night working
Treatment for insomnia?
most hypnotics enhance GABAergic circuits
What is narcolepsy?
What is it linked to?
What stage of sleep control is dysfunctional?
Deficiency of what molecule?
Falling asleep repeatedly during the day and disturbed sleep during the night
Cataplexy is linked (sudden, brief loss of voluntary muscle tone, often triggered by strong emotions e.g. laughter)
Dysfunction of control of REM sleep
Orexin/hypocretin deficiency
Where is the orexin system found?
LATERAL HYPOTHALAMUS
SHIFT WORKING - Can lead to A, B and an increased risk for conditions like C, D and E
sleep disorders, fatigue
diabetes, cancer and obesity
How to improve sleep quality? (8)
Fixed times for sleeping and waking up Creating a relaxing bedtime routine Only go to bed when you feel tired Maintaining a comfortable sleeping environment Not napping Avoiding caffeine, nicotine and alcohol late at night Avoiding heavy meals at night Not using electronic devices before bed
What is consciousness defined as
state of being aware of and responsive to your surroundings
3 elements of consciousness?
LEVEL- are you drowsy, anaesthetised, wide awake?
CONTENT- what are you conscious of?
SELF- we have an attachment to self
The XX in the RAS has neurones which project to A and B
XX reticular formation
A thalamus
B cortex
A cortical site of consciousness?
frontoparietal cortex
what midbrain and pons structures are involved in the RAS and what are their NT?
- Ventral tegmental area (Dopaminergic neurones)
- Locus coeruleus (NA neurones)
REGIONS OF THE BRAIN INVOLVED IN CONSCIOUSNESS MAY OR MAY NOT BE DETERMINABLE BY THE FOLLOWING 3 FACTORS:
REGIONS OF THE BRAIN INVOLVED IN CONSCIOUSNESS MAY OR MAY NOT BE DETERMINABLE BY THE FOLLOWING:
What is the default mode network
Network when we day dream or introspect
How do you quantify level of consciousness?
Using transcranial magnetic stimulation and EEG - perturbational complexity index
How does circadian control of sleep work?
Special cells in the retina detect decrease in light level and activate the suprachiasmatic nucleus of hypothalamus
Suprachiasmatic nucleus modulates sleep-wake circuits and stimulates pineal gland to secrete melatonin
Melatonin synchronises physiological processes with day length
Evidence that sleep is necessary?
- Most/all animals sleep
- Sleep deprivation is detrimental
- Sleep is regulated accurately
NEURAL CORRELATES OF CONSCIOUSNESS (NCC) defines:
the minimal neuronal mechanisms jointly sufficient for any one specific conscious experience
What is PERTUBATIONAL COMPLEXITY INDEX (PCI):
A method of quantifying brain complexity using transcranial magnetic stimulation and EEG
A method of quantifying brain complexity ?
PERTUBATIONAL COMPLEXITY INDEX (PCI):
Three areas the Glasgow Coma scale tests?
Eyes open?
Verbal responses?
Motor Responses?
3 main disorders of consciousness and their state of wakefullness/awareness?
Coma - absent wakeful and awareness
Vegetative state - wakeful with absent awareness
Minimally conscious state - wakefulness with minimal awareness
What is covert awareness of vegetative states?
Patients were taken in a vegetative state and asked yes/no questions at their bedside, and then taken to an fMRI scanner and asked this time to imagine they were playing tennis for yes, or cleaning their house for no- the controls had very similar reactions to the vegetative participants- suggests the same response (demonstrates that vegetative patients are still aware)
NEGLECT in consciousness disorders is? And what causes it?
Loss of a conscious awareness of one side of the brain- often happens due to stroke and accompanies a hemianopia
Patients may leave the left half of their meal for example- just not conscious of it
General causes of coma?
Metabolic
Diffuse intracranial
Hemisphere lesion
Brain stem
Metabolic causes of coma?
- Drug overdose
- Hypoglycaemia
- Diabetes
- “the failures” (renal failure, liver failure)
- hypercalcaemia
Diffuse intracranial
causes of coma?
- head injury
- meningitis
- Subarachnoid haemorrhage
- Encephalitis
- Epilepsy
- hypoxic brain injury
Hemisphere lesion
causes of coma?
- cerebral infarct
- cerebral haemorrhage:
subdural
extradural - abscess
- tumour
Brain stem causes of coma?
- brainstem infarct
- tumour
- abscess
- cerebellar haemorrhage
- cerebellar infarct
