8.2 Consciousness Flashcards
What neural components are required to be conscious?
Think, need to be awake and have thoughts
- Cerebral cortex - ‘thoughts’ arise here
- Reticular formation (reticular activating system in brainstem) - keeps the cortex ‘awake’
What connects the reticular formation and the cortex?
They are connected by reciprocal excitatory projections, forming a positive feedback loop
(positive feedbacks seen when there is a binary outcome - sleep/awake)
What are the three major relay nuclei in the Reticular formation?
- Excitatory cholinergic (ACh) - basal forebrain to the cortex
- Excitatory histaminergic (histamine) - hypothalamus to the cortex
- Excitatory glutamatergic (glutamate) - thalamus to the cortex
(Reticular formation also sends projections down the cord, responsible for maintaining muscle tone)
Which three components does the Glasgo Coma Scale look at?
- Eye movements
- Motor response
- Verbal response
How does scoring for the Eye Component of the GCS work?
(4) = Spontaneous eye opening = normal cortical and brainstem function
(3) = Response to speech = Slightly diminished cortical function but functioning brainstem
(2) = Response to pain = Impaired cortical function but brainstem preserved so reflex eye opening occurs
(1) = No response = severe damage to brainstem +/- cortex
How does scoring for the Motor Response of the GCS work?
(6) = Obeys commands = normal function from auditory system to brainstem/cord
(5) = Localises to stimuli = Diminished higher cortical function but working connections from sensory to motor cortex
(4) = Withdraws to pain = still a ‘physiological’ reflex response to stimuli
(3) = Flexor response to pain = lesion above the red nuclei, ‘semi-physiological’
(2) = Extensor response to pain = Lesion below the red nuclei - not physiological at all
(1) = No response to pain = severe damage to brainstem +/- cortex
How does scoring for the Verbal Response of the GCS work?
(5) = Oriented in time/place = normal cortical function
(4) = Confused conversation = diminished higher cortical function but language centres still functioning adequately
(3) = Inappropriate words = language centres have been damaged
(2) = Incomprehensible sounds = cortical damage with brainstem mediated groans
(1) = No response = severe damage to brainstem +/- cortex
What is the most points given to each component of the GCS?
Eye responses = 4 points max
Motor response = 6 points max
Verbal response = 5 points max
(Total of 15 points maximum and 3 points minimum)
How does the Electroencephalogram (EEG) work?
Measures the combined activity of thousands of neurones in a particular region of cortex.
Good for detecting neuronal synchrony (which occurs in pathological and physiological processes)
Has HIGH TEMPORAL resolution, LOW SPATIAL resolution (temporal = measurement with respect to time, milliseconds in EEG; low spatial due to electrodes being a couple cm apart?)
What are the functions of sleep?
- Energy conservation/repair
- Memory consolidation
- Clearance of extracellular debris - CSF flows during our sleep and is thought to proteins which are toxic to our brains.
How many stages are there of sleep?
4 major stages + REM sleep;
Typically pass through around 6 cycles of sleep per night.
What are the different stages seen as you fall asleep on an EEG pattern?
Awake with eyes open Awake with eyes closed Stage 1 sleep Stage 2/3 sleep Stage 4 sleep REM sleep
What are the waves like when you are awake with eyes open?
Beta waves - irregular, 50Hz
What are the waves like when you are awake with eyes closed?
Alpha waves - irregular, 10Hz
What are the waves like when you are in Stage 1 of sleep?
Background of alpha waves + interspersed theta waves
Theta waves at around 5Hz, regular
