Consciousness Flashcards
What is Locked-in syndrome?
Person appears unconscious, but actually has complete awareness but an inability to respond.
Person goes through sleep-wake cycles which can be measures on an ECG, and may make some isolated meaningful movements e.g eye movements.
What is a minimally conscious state?
Patient has intermittent periods of wakefulness and sleep, and displays some meaningful behaviour.
What is a persistent vegetative state?
Patient lacks awareness, but goes through sleep-wake cycles.
The patient will only display reflexive and non-purposeful behaviour.
What is a chronic coma?
The patient lacks awareness and lacks sleep-wake cycles. The patient only displays reflexive behaviour.
What is brain death?
Patient lacks awareness, lacks sleep-wake cycles, lacks brain-stem reflexes and only has spinal reflexes.
The patient has lost the ability to ever regain consciousness and has lost the capacity to breathe on their own.
How do PET scans measure brain activity, and what particular consciousness disorder can they be used to show?
The patient is injected with radioactive glucose, and the brain takes up a lot of glucose so this can be used to show brain activity. Where the glucose is taken up it releases positrons.
Areas of higher brain activity are warmer colours (orange and red). Areas of lower brain activity are cooler colours (green, blue, black).
Locked-in syndrome can be shown when a patient with no outward signs of awareness has lots of brain activity.
What is normal loss of consciousness?
Going to sleep.
What does AVPU mean when you are assessing someone’s consciousness?
Awake?
Respond to verbal stimuli?
Respond to painful stimuli?
Completely unresponsive?
What is the maximum and minimum score on the Glasgow Coma Scale?
Max = 15 Min = 3
What are the three categories of the Glasgow Coma Scale?
Best eye response
Best verbal response
Best motor response
What are the scores available in best eye response?
4 = spontaneous eye opening 3 = eye opening in response to speech 2 = eye opening in response to pain 1 = no response
What are the scores available in best verbal response?
5= orientated 4 = confused conversation 3 = inappropriate speech 2 = incomprehensible speech 1 = no verbal response
What are the scores available in best motor response?
6 = obeying command 5 = localising response to pain 4 = withdraws from pain 3 = abnormal flexor response to pain 2 = extensor posturing to pain 1 = no response to pain
What does a GCS score more than 9 mean?
You’re not in a coma?
What is true of 90% of patients with a GCS score less than or equal to 8?
They are in a coma
What is meant by a GCS score between 9 and 11?
Moderately severe injury?
What is meant by a GCS score above or equal to 12?
Minor injury.
What is the definition of brain death?
Patient has irreversibly lost the capacity for consciousness and the capacity to breathe on their own.
What are the 3 NHS criteria for brain death?
1) person is unconscious and not responding to outside stimulation
2) person’s heartbeat and breathing can only be maintained by a ventilator
3) there is clear evidence that serious brain damage has occurred, so the unconsciousness isn’t being caused by primary hypothermia, depressant drugs, circulatory or metabolic or endocrine disturbances, apnoea caused by muscle relaxants or cervical cord injury, which are all potentially reversible
What are some of the reflexes tested when diagnosing brain death?
Pupillary reflex (shine light in eye)
Corneal reflex (stroke cornea with cotton bud, do they blink?)
Vestibulo-ocular reflex (ice cold water in ear, eyes move?)
Gag reflex (stimulate posterior pharynx, or catheter into trachea)
Respiratory (breathe on their own within 5 minutes of ventilator being disconnected?)
What is the Reticular Activating System?
Top part of the reticular formation in the brainstem, involved in consciousness.
Define consciousness.
The state of being both aware of and responsive to your surroundings.
What are the 4 sets of nuclei in the reticular formation, their locations and their neurotransmitters?
1) Locus coeruleus - noradrenaline, in the pons
2) Raphe nuclei - midline of midbrain and pons and medulla, serotonin
3) Ventral tegmental area - ventral region of the midbrain, dopamine
4) Cholinergic nuclei - in the basal forebrain and dorsolateral pons, acetylcholine
Which of the reticular formation nuclei contribute to synaptic plasticity and are involved in learning and memory?
Cholinergic nuclei
What does destruction of the locus coeruleus result in?
Loss of rapid eye movement (REM) sleep.
What is hyperactivity of the locus coeruleus linked to?
Depression.
What does damage to the anterior hypothalamus lead to?
Insomnia
What does damage to the posterior hypothalamus lead to?
Sleeping sickness
Where is the reticular nucleus, and what does it do?
On the outside of the thalamus, tonically inhibits the thalamus.
What is the difference between the result of stimulating the reticular activating system and stimulating the thalamus?
Stimulating RAS leads to wakefulness
Stimulating thalamus causes sleep
What happens to the cholinergic fibres of the reticular activating system and the reticular nucleus when you’re awake versus when you’re asleep?
Awake = cholinergic fibres of ascending reticular activating system increase firing, so the reticular nucleus is inhibited and the sensory thalamus facilitated. This means the thalamocortical neurones are active and there is a desynchronise EEG with randomly firing thalamocortical circuits. Asleep = cholinergic fibres decrease firing, so reticular nucleus active and tonically inhibiting thalamus. Thalamocortical neurones in slow rhythm, EEG is synchronous.
Which 3 neurone pathways produce the oscillations on an EEG when observing sleep?
Thalamocortical (in thalamus)
Corticothalamic (in cortex)
Reticular (in reticular nucleus)
What is the difference between the firing of the thalamocortical circuits when you’re awake and when you’re asleep?
Awake = fire randomly (desynchronous) Asleep = oscillate (so produce oscillatory EEG)
How long are sleep cycles?
90 minutes
How do the waves on an EEG change as you move from wakefulness to deeper sleep?
They become higher amplitude and lower frequency
What are the two stages of being awake?
Beta waves - alert, low amplitude and high frequency waves
Alpha waves - drowsy, higher amplitude and lower frequency
What is stage 1 of non-REM sleep?
Theta rhythms, this is when you get hypnagogic hallucinations and hypnic jerks.
What is stage 2 of non-REM sleep?
Sleep spindles and K complexes, which keep you asleep even when you hear a noise.
What are stages 3 and 4 of non-REM sleep?
Delta waves - slow wave sleep, deepest sleep
What is REM sleep?
Looks like wakefulness, because the mind is very active but the body is paralysed.
Beta waves on the EEG - low amplitude high frequency.
How do the amounts of deep sleep and REM sleep change through the night?
In the earlier part of the night there is more deep sleep, in the later part of the night there are longer periods of REM sleep.
What are the 2 main types of sleep?
1) Synchronised (non-REM sleep) - EEG waves are slow and synchronised, and it is do,instead by low frequency activity (delta waves
What are 3 conditions that sleep disorders can be indicators of?
Orthopnoea (dyspnoea)
Enuresis (lack of bladder control)
Epilepsy (neuronal seizures)
What are some short term consequences of sleep deprivation?
Slower reflexes Memory disorders Muscle fatigue Mood swings Aggressive behaviour Disorientation Hallucinations (spontaneously going into REM sleep)
What are some long term consequences of sleep deprivation?
Obesity, diabetes, hypertension
How long are days according to circadian rhythms?
24.5 to 25.2 hours
How are circadian rhythms generated?
Neurones from the retina project to the suprachiasmic nucleus in the hypothalamus (just above the optic chiasm). The suprachiasmic nucleus secretes vasopressin to local brain areas.
The suprachiasmic nucleus indirectly modulates the pineal gland, which secretes the sleep promoting hormone melatonin.
