Consciousness Flashcards
Define wakefulness.
ability to open your eyes and have basic reflexes such as coughing, swallowing and sucking
Compare wakefulness and awareness.
Awareness - more complex thought processes.
Wakefulness - presence of basic reflexes.
Define consciousness.
processes enabling us to experience world; distinct from automatic behaviours that occur unconsciously
How does complexity change with levels of consciousness?
will be reduced when asleep or unconscious, and higher when awake
What are the neural correlates of consciousness?
minimum neuronal mechanisms sufficient for one specific conscious experience - localises to a posterior hot zone including sensory areas
What is the role of the RAS?
modulate alertness and consciousness.
Explain the structure of the reticular formation.
polysynaptic network in core of medulla, pons and upper medulla.
Contains NA and Ach NT neurones.
Project into cortex via thalamus to increase activity.
What are the reticular formation inputs?
Touch/pain from ascending tracts
Vestibular from medial vestibular nucleus
Auditory from inferior colliculus
Visual from superior colliculus
Olfactory via medial forebrain bundle
What are the reticular formation outputs?
To the ventral tegmental area (dopaminergic neurones) in midbrain
To the locus coeruleus (noradrenergic neurones) in the pons
To the thalamus (cholinergic neurones)
Explain electroencaphalography.
Using scalp electrodes to measure brain activity and determine frequency of brain waves.
What are the frequencies of deltla, theta, alpha and beta brain waves,
Delta: <4Hz
Theta: 4-8Hz
Alpha: 8-13Hz
Beta: 13-30Hz
-What do beta, alpha, theta and delta waves look like? Also describe sleep spindles and REM sleep waves.
What is the Glasgow Coma Score used for?
determine level of consciousness
Explain the response to stimulation of a patient in a coma.
ABSENT wakefulness, ABSENT awareness; unrousable unresponsiveness where patient cannot be woken, does not have a normal sleep cycle and has no response to pain
Explain the responses of a patient in a vegetative state to stimulation.
wakefulness, ABSENT awareness; preserved capacity for spontaneous/stimulus arousal (sleep wake cycles and range of reflexive behaviour) but complete absence of behavioural evidence for self or environmental awareness - destruction of cortex and hemispheres but intact RAS
Explain the responses of a minimally conscious patient to stimulation.
wakefulness, MINIMAL awareness; minimal but clearly discernible behavioural evidence of self/environmental awareness - characterised by inconsistent and reproducible responses above level of spontaneous/reflexive behaviour
Explain the responses of a patient with locked in syndrome to stimulation.
wakefulness and awareness; intact cortex and RAS, but damage to ventral pons means can’t move or talk
Table used to determine GCS score.
Name some metabolic causes of coma.
overdose, hypoglycaemia, diabetes, hypercalcaemia
Name some diffuse intracranial causes of coma.
head injury, meningitis, subarachnoid, encephalitis, epilepsy, hypoxic brain injury
What hemisphere lesions might lead to a coma?
cerebral infarct, cerebral haemorrhage, abscess, tumour
What brainstem lesions might lead to a coma?
brainstem infarct, tumour, abscess, cerebellar haemorrhage, cerebellar infarct
Define brain death.
Irreverisble coma due to brainstem death.
Life support to body.
Define coma.
unreactive unresponsiveness, with neither wakefulness or awareness, but intact brainstem
Define persistent vegetative state.
irreversible coma due to brainstem-cortex disconnection or widespread cortical damage; brainstem still functions reflexively, and sleep-wake cycle present; patient is not conscious and unaware of surroundings.
