8. Consciousness Flashcards
what is consciousness?
the awareness of the external environment and internal states
what is arousal?
goal seeking behaviour and avoidance of noxious stimuli
what two components are required for consciousness to be functioning?
- cerebral cortex - site where conscious thought arise
- reticular formation - inputs into corttex to keep it ‘awake’
these must be connected by reciprocal excitatory projections, forming a positive feedback loop
how are outputs from the reticular formation connected to the cortex?
via three major relay nuclei:
- basal forebrain nuceli sending excitatory cholinergic fibres to cortex
- hypothalamus sends excitatory histaminergic fibres to cortex
- thalamus sends excitatory glutamatergic fibres to cortex
also projections down the cord responsible for maintaining muscle tone
what scale is used to commonly assess consciousnes?
glasgow coma scale
describe the features of eye opening in the gcs?
- spontaneous eye opening
- response to speech (less cortical function but functioning brainstem)
- response to pain (even less cortical function)
- no response (severe dmaage to brainstem and/or cortex)
describe the features of motor response in the gcs?
- obeys command
- localises to stimuli (dimished higher cortical function but still connections from sensory to motor cortex)
- withdraws to pain (physiological reflex response to stimuli)
- flexor reponse to pain (lesion above red nuclei, mostly physiological
- extensor response (lesion below red nuceli, not physiological)
- no response (severe damsge in brainstem and/or cortex)
describe the features of the verbal response in the gcs?
- oriented in time/place
- confused conversation (dimished higher cortical function but language centres functioning)
- inappropriate words (language centres damaged)
- incomprehensible sounds (cortical damage with brainstem mediated groans)
- no response (severe damage to brainstem and/or cortex)
what piece of equiptment is used to measure the activity of neurones in the brain but especially in cortical region?
the electroencephalogram
what are the advantages and disadvantages to this piece of equiptment?
high temporal resolution
good for detecting neural synchrony
low spatial resolution
what phenomonen occurs when we are asleep or during epilepsy>
neural synchrony
what are the functions of sleep?
energy conservation and repair?
memory consolidation?
clearance of extracellular debris?
resetting of cns?
what are the stages of sleep and what is measured?
4 major stages + rem sleep
around 6 cycles of these stages per night
1. awake with eyes open: beta waves - irregular, 50Hz
2. awake with eyes closed: alpha waves - regular, 10Hz
3. stage 1 sleep: background of alpha and interspersed theta waves, 5Hz and regular
4. stages 2/3: theta and interspersed sleep spindles (high frequency bursts arising from thalamus) and K complexes (intrinsic rate of the cortex)
5. stage 4 sleep: delta waves, regular, 1Hz
REM sleep - similar to beta waves, when drraming occurs so similar to when conscious
what is the mechanism of enabling non rem sleep?
deactivation of the reticular activating system (by removing sensory inputs so fewer positive influences on positive feedback loop) and inhibition of the thalamus
how is rem sleep initated?
by neurones in the pons
