Lecture 11 - Brainstem, Arousal, Sleep And Consciousness Flashcards
What is the Definiton of arousal?
Emotional state associated within a goal or avoiding something noxious or toxic
What is the definition of sleep?
The readily reversible state of reduced responsiveness to and interaction with theee environment
What is the definition of consciousness/
Hard to define
It’s related to the awareness of external environment and internal states
What are the 2 main components required for consciousness?
Functioning cerebral cortex
Functioning reticualr formation
What is the reticular formation/where is it found?
Diffuse network of interneurones running entire length of brainstem continous with white matter tracts from teh spinal cord and diencephalon
What are the 3 columns of the reticular formation?
Median
Medial
Lateral
What is the function of the median column of the reticular formation?
Arousal
Emotion
What is the function of the medial column of the reticular formation?
Somatosensory input processing
What is the function of the lateral column of the reticular formation?
Cranial nerve activity
Micturition
What are the 2 main inputs to the reticular formation?
Cortex
Sensory system
What is the overall role of the reticular formation?
Keeps the cortex awake/functioning (reticular activating system does this)
Integrate, relay and coordinate vital life functions and protective reflexes
What are the 3 main cortical regions which the reticular formation sends impulses to?
Thalamus
Hypothalamus
Basal forebrain nuclei
What neurotransmitter travels along the axons which are sent from the reticular formation to the thalamus?
Glutamate
What neurotransmitter travels along the axons which are sent from the reticular formation to the Hypothalmus?
Histamine (H hypothalamus H Histamine)
What neurotransmitter travels along the axons which are sent from the reticular formation to the basal forebrain nuclei?
Acetylcholine (ACh)
What type of feedback loop occur between the cortex and reticular formation when there’s a binary outcome (sleep or awake e.g)?
Postive feedback
How does the reticular activating system maintain wakefulness?
Reticualr activating system receives excitatory input from cortex, projects it’s own excitatory input back to cortex forming + feedback loop
Info sent to cortex amintaingni arousal and consciousness and blocking pathways promoting sleep
What nuclei of the reticular formation send the projections to the hypothalamus, thalamus and basal forebrain nuclei?
Median raphe
What are the 2 ways by which we can assess/measure cortical function?
Electroencephalogram (EEG)
Glasgow Coma Scale (GCS)
What is the Glasgow Coma Scale?
Clinical assesment of consciousness used to measure level of cerebral activity
Useful to localise lesion to cerebral cortex or brain stem
What 3 responses does the Glasgow Coma Scale (GCS) measure?
EMV
Eye repsonse
Motor response
Verbal response
What is better, a high GCS score or lower GCS score?
Higher GCS score
Indicates higher level of CNS function and less CNS dameage
What is the GCS scored out of?
15
What is the significance of a patient spontaneously opening their eyes? (GCS)
Cortical function is fine
What is the significance of a patient only opening their eyes when you tell them to? (GCS)
Slightly diminished cortical function but still functioning brainstem
What is the significance of a patient only opening their eyes when receiving pain stimulus? (GCS)
Impaired cortical function
Brainstem preserved since reflex functional
What is the significance of a patient not opening their eyes? (GCS)
Severe damage too brainstem (maybe also cortex)
What is the significance of a patient being able to obey commands for the motor repsonse part of GCS?
Normal function
What is the significance of a patient being able to localise to stimuli after a painful stimulus for the motor repsonse part of GCS?
Diminished higher cortical function but connections from sensory and motor cortex fine
What is the significance of a patient withdrawing to pain for the motor repsonse part of GCS?
Still a physiological reflex repsonse to stimuli so brainstem is fine
What is the significance of a patient having a flexor response to pain for the motor repsonse part of GCS?
Lesion above the red nuclei
What is the significance of a patient having a extensor response to pain for the motor repsonse part of GCS?
Deep cortical lesion below the red nuclei
What is the significance of a patient not having a response to pain for the motor repsonse part of GCS?
Severe damage to Brain stem and or cortex
What is the significance of a patient having a correct verbal response to a question for the GCS score?
Normal cortical function
What is the significance of a patient having a confused verbal response to a question for the GCS score?
E.g giving the wrong day of the week
Diminished higher cortical function
What is the significance of a patient having an inappropriate verbal response to a question for the GCS score?
E.g saying sandwich when asked the day of the week
Language centres have been damaged (cortical function impaired)
What is the significance of a patient having a non worded response like groaning or moaning response to a question for the GCS score?
Significant cortical damage where the brainstem is taking over
What is the significance of a patient having no verbal response to a question for the GCS score?
Severe damage to brainstem and or cortex
What is an electroencephalogram?
Measure electrical activity of the cerebral cortex from the scalp
What does an electroencephalogram measure?
Measures how synchronous neuronal activity is
When are the brains neurones most synchronous?
Non dreaming sleep
Drugged or coma
Essentially when there’s very little stimuli
When are the Brains neurones least synchronous?
When highly alert, waking or dreaming stage of sleep (REM)
How is highly synchronous neuronal/cortical activity represented on an electroencephalogram?
High amplitude and low frequency = synchronous
How is non synchronised neuronal/cortical activity represented on an electroencephalogram?
Low amplitude and High frequency
How is non synchronised neuronal/cortical activity represented on an electroencephalogram?
Low amplitude and High frequency
How does sleep occur?
Reticular activating system gets deactivated by the THALAMUS
So cortical activity is reduced so sensory input is reduced
Neuronal activity synchronises
Why do we need sleep?
Not completely understood:
Rest and recover?
Conservation of energy?
Protection?
Memory?
Clearance of metabolites?
What system removes toxic metabolites from the brain?
Glymphatic system
Why is the glymphatic system important?
Removes harmful proteins
Most active at night
Lack of sleep can lead to Alzheimer’s due to toxic protein build up
What are the 2 types of sleep?
REM sleep
Non REM sleep
What are the 2 types of sleep?
REM sleep
Non REM sleep
How long does each REM - Non-REM sleep cycle last?
Both together is about 90mins
How can you describe the muscle tone in Non-REM sleep?
Reduced muscel tone but can still move
(why you can jerk in night)
What type of activity are seen with the neurones in Non-REM sleep?
High voltage + Low frequency (synchronous)
How many stages of Non-REM sleep are there?
4
How can you describe the muscle tone in REM sleep?
Muscle paralysis and Atonia
Which part of the brain controls REM sleep?
Pons
What functions are preserved in REM sleep?
Eye movements and other cranial nerve function
Autonomics (Penile erection and loss of Thermoregulation)
What is nocturnal bruxism?
What causes it?
Grinding of teeth in sleep
Facial nerve overly active in sleep causing teeth to grind
What waves are seen when awake with eyes open?
Beta waves irregular 50Hz
What waves are seen while awake with eyes closed?
Alpha waves - regular 10Hz
What waves are seen in Stage 1 of sleep?
Alpha and Theta waves at 5Hz
What waves are seen at stages 2+3 of sleep?
Theta, sleep spindles and k-complex
What are sleep spindles??
High frequency bursts coming from the thalamus
What are k complex’s?
Slow synchronous activity
The intrinsic rate of the cortex
What waves are seen in stage 4 sleep?
Delta waves (regular 1Hz)
Label the EEG on slide 15
What is insomnia?
Inability to sleep
Normally due to anxiety, depression or other mental or physical illness
What is narcolepsy?
Dysregulation of your circadian rhythm
What is sleep apnoea?
Temporary occlusion of the airway during sleep resulting in intermittent sleep
What is the defintion of brain death?
Damage to brainstem and cortex (flat EEG)
What is the defintion of coma?
Widespread brainstem and cortical damage
Has disordered EEG patterns and no sleep wake cycle
What is the defintion of persistent vegetative state?
Cortical damage, the brainstem is fine but you have disordered EEG pattern, some eye movements and repsonse to stimuli
What is locked in syndrome/what causes it?
Occlusion of the basilar/pontine arteries leads to loss of function of the corticospinal tract
Person cant move but can move their eyes and understand everything
Why can a patient with locked in syndrome still move their eyes?
The edinger Westphal nucelus in the midbrain is unaffected
