Arousal, Sleep + Consciousness Flashcards
Define arousal
Emotional state associated with a goal or avoiding something noxious/toxic usually goal orientated
Define sleep
The readily reversible sate of reduced responsiveness to + interaction with the environment
Define consciousness
Difficult to define mainly to do with awareness of internal + external world
What are the two main components needed for consciousness?
Functioning cerebral cortex
Reticular formation
What is the reticular formation?
Diffuse network of specialised interneurones running the entire length of the brainstem
How is the reticular formation divided?
Median, medial + lateral columns
How is the cortex and reticular formation connected?
Reciprocal excitatory projections
Forming positive feedback loop
What are the 2 components required for consciousness + their function in this
- Cerebral cortex: site where conscious thoughts arise**
- Reticular formation: circulatory that keeps cortex awake
Describe the outputs of the reticular formation to the cortex
Reticular formation sends cholinergic (excitatory) projections to 3 major relay nuclei:
- basal forebrain nuceli send excitatory cholinergic fibres to cortex
- hypothalamus sends excitatory histaminergic fibres to cortex
- thalamus send excitatory glutamatergic fibres to cortex
What fibres connect the basal forebrain nuclei to cortex?
Excitatory cholinergic fibres
What fibres connect the hypothalamis to cortex?
Excitatory histaminergic fibres
What fibres connect the thalamus to cortex?
Excitatory glutamatergic fibres
What is used to assess consciousness clinically?
GCS
Glasgow coma scale
What are the 3 components of GCS?
Eye opening
Motor response
Verbal response
Eye opening GCS scoring + what it suggests
- 4: spontaneous eye opening | normal cortical + brainstem function
- 3: response to speech | slightly reduced cortical function w functional brainstem
- 2 response to pain | impaired cortical function but brainstem preserved
- 1: no response | severe damage to brainstem +/- cortex
Motor response GCS scoring
What does it suggest?
- 6: obeys commands | normal function w connections between brainstem + auditory system
- 5: localises stimuli | diminished higher cortical function but in tact connections between sensory + motor cortex
- 4: withdraws to pain |still physiological response to stimuli
- 3: flexor response to pain |lesion above red nuclei
- 2: extensor response to pain | lesion below red nuclei
- 1: no response to pain | severe damage to brainstem +/- cortex
Verbal response GCS scoring
What does it suggest?
- 5: oriented in time/place | normal cortical function
- 4: confused conversation | diminished higher cortical function but language centres in tact
- 3: inappropriate words |language centre damaged
- 2: incomprehensible sounds | cortical damage with brainstem mediated groans
- 1: no response: severe damage to brainstem +/- cortex
What is GCS score range?
3-15
What does an electroencephalogram measure?
Synchronous neuronal activity
Larger the amplitude - more synchronous activity
What are the suspected functions of sleep?
Energy conservation
Memory consolidation
Clearance of extracellular debris
Resetting of CNS
Describe the resolution of EEG
Good temporal resolution
Poor spatial resolution
What do results of EEG represent?
- high frequency + low amplitude: alertness + waking or dreaming stage of sleep (REM)
- low frequency + high amplitude: non dreaming sleep (non REM), drugged or coma
Types of sleep
REM
Non REM
Length of cycles in sleep + how many each night?
90 mins
~ 6 cycles
Describe Non REM sleep
- deactivation of reticular activating system due to thalamus inhibition
- split into 4 stages
- reduced muscle tone but not paralysed
- EEG shoes high voltage + low frequency
Describe REM sleep
- EEG similar to beta waves
- dreaming occurs in stage > EEG similar to conscious patient (low voltage + high frequency)
- mediated by pons
- muscle paralysis + Antonia
- eye movements + cranial nerve function + autonomic effects preserved
List three sleep disorders
Insomnia
Narcolepsy
Sleep apnoea
What is insomnia?
What is it due to??
Inability to sleep
Due to anxiety or depression or another mental illness
What is narcolepsy?
Dysregulation of circadian rhythm
Randomly + uncontrollably fall asleep
What is sleep apnoea?
Who is it common in?
- Temporary occlusion of airways during sleep resulting in intermittent sleep
- Often in obese people due to excess neck fat > ompression of airways
What does sleep apnoea cause?
Excessive daytime sleepiness
What is locked in syndrome due to?
Occulsion of basilar or pontine arteries
What is locked in syndrome?
All somatic motor function lost expect eye movement
What is preserved in REM sleep?
- eye movements
- cranial nerve function
- autonomic effects e..g penile erection and loss of thermoregulation
Compare EEG in REM + non REM sleep
- REM: high frequency + low voltage
- non REM: high voltage + low frequency
What are the stages of sleep + their EEG results?
- awake with eyes open: beta waves
- awake with eyes closed: alpha waves
- stage 1: background of alpha + interspersed theta waves
- stage 2/3: background of theta + interspersed sleep spindles + K complexes
- stage 4: delta waves
- REM sleep: similar to B waves - high frequency + low voltage
What are sleep spindles?
What stage of sleep are they seen in?
High frequency bursts arising from thalamus
In stage 2/3
What do K complexes represent?
What stage of sleep are they seen in?
The emergence of the intrinsic rate of the cortex before deepest stage of sleep
In Stage 2/3
Name some conditions of disordered/absent consciousness
Coma
Brain dead
Persistent vegetative state
Narcolepsy
What structure prevents sensory information being transmitted to cortex during sleep?
Thalamus
Classes of medication which could cause drowsiness
Anticholinergics
Anti histamines
Anti depressants
Anti psychotics
Anti emetics
Ways to reduce sensory input to brain when trying to fall asleep
Comfy clothes
Dark room
Good temperature room
Reduced noise e.g. ear plugs
Explain the control of consciousness in the brain
- controlled by the reticular formation
- sends projections to thalamus, hypothalamus + basal forebrain nuclei
- this forms activating systems
- these 3 areas send excitatory projections to the cortex > stimulates cortex to stay awake
. - basal forebrain nuclei - cholinergic B-C
- hypothalamus - histaminergic H-H
- thalamus - glutaminergic G+T
