Consciousness and Pain Flashcards
What is consciousness?
Consciousness stems from sentience- awareness of internal or external existence
What two dimensions can consciousness be considered across?
Level of arousal/wakefulness and representational capacity for consciousness
What are the missing labels on the diagram? (exclude 5 and 6)
Is there a sleep-wake cycle in the following:
(a) coma
(b) vegetative state
(c) minimally conscious state
(d) locked-in syndrome
(a) No
(b) yes
(c) yes
(d) yes
What is locked in syndrome?
Usually occurs after a brain-stem stroke, where patients are unable to move to sense anything with their bodies. Can sometimes move eyes
What are 3 factors of the sleep wake cycle?
Circadian rhythm
Homeostasis
Cognitive pressure
What is the circadian rhythm?
Spontaneous 24 hr cycles that govern many things.
In line with melatonin (peak during day), cortisol (peak in the morning) and body temperature patterns throughout the day
Also influenced by light
What nucleus gets input from the retina about light levels and affects the circadian rhythm?
Suprachiasmatic nucleus
What is the ‘c process’ and ‘s process’ of sleep wake cycle?
Circadian rhythm= c
Homeostasis= s
What does the circadian rhythm regulate?
It regulates the body’s internal biological processes and alertness levels. This is what controls the timing of sleep and it coordinates the light-dark cycle of day and night. Your circadian rhythm is what regulates your body’s sleep patterns, feeding patterns, core body temperature, brain wave activity, and hormone production
What hormones rise and fall during the circadian rhythm?
Melatonin peaks during the day
Cortisol peaks in the morning
What is homeostasis (related to sleep wake cycle)?
the accumulation of sleep-inducing substances in the brain. It’s an internal biochemical system that operates like a timer, generating homeostatic sleep drive or the need to sleep after a certain amount of time awake
What do the graphs of process c and process s look like?
What did Constantin Van Economy find with hypothalamus damage?
Patients with frontal damage= insomnia state
Patients with posterior damage= zombie like, awake but not fully conscious
How are we sent off to sleep?
The ventrolateral pre-optic area (VLPO) sends out inhibitory GABAergic neurotransmitters that project to a number of conscious controlling centres
How do we wake up?
The tubberomammilary nucleus switches on histamine -> wakes up the cortex.
Then the posterior lateral hypothalamus secretes orexin/hypocretin -> activates the reticular activating system -> releases dopamine and AhC.
What is narcoplexy?
Low levels of CSF orexin, causes patient to fall asleep at inappropriate times
What are the 4 stages of sleep?
Awake, light, deep and REM
How long does a sleep cycle last?
Around 90 mins
What happens to the proportion of REM sleep as we sleep longer?
REM sleep (dream state) increases in proportion
What does the graph of sleep stages look like throughout the night?
What are some non-REM sleep disorders?
Sleep walking, confusional arousals and night terrors. Occurs in deeper stages of sleep
What is REM sleep behaviour disorder?
When patients act out their dreams. A failure of inhibition of movement during sleep
What is REM sleep behaviour disorder strongly predictive of?
alpha-synucleinopathies (abnormal accumulation of insoluble α-synuclein), such as Parkinson’s disease or dementia with Lewy bodies
What is isolated sleep paralysis?
Inhibition may not disengage when patients wake up and patients may be temporarily paralysed
What is the Glasgow coma scale?
A measure of how conscious someone is, but should be thought of a as more of a holistic measurement of brain function.
What are the different aspects of the GCS?
Eye opening response- 4 points
Best verbal response- 5 points
Best motor response- 6 points
Out of 15 points
How is eye opening response scored in the GCS?
How is best verbal response scored in the GCS?
How is best motor response scored in the GCS?
What is the criticism of the GCS?
It does not directly measure consciousness- e.g. someone with locked in syndrome will score very low on GCS but are still conscious
Damage to what brain structures can cause problems with arousal?
Diencephalon
Brainstem
Bilateral thalamus
Global cortex
Why can damage to the diencephalon cause problems with arousal?
Contains the posterolateral hypothalamus, which is the ‘wake up switch’
Why can damage to the brainstem cause problems with arousal?
Contains the reticular activating system which releases ACh and dopamine to wake brain up.
What are the main causes of a patient who has blacked out?
Brain without fuel- oxygen, glucose, low BP
Brain with a problem- raised ICP, electrical failure, stroke, acid base disturbance or inflammation
What is asphyxia?
Lack of oxygen
What are the 3 categorises of nervous system dysfunction?
Problem with the prerequisites needed (pathways and systems)
Reality modelling and predictive value problem (capacity to model objective reality, set goals and predict outcomes)
Problem with acting in the world (capacity to generate behaviour)
Why will disruption to the brainstem cause problems with arousal?
Contains the reticular activating system- projects AhC to thalamus and cortex that is picked up by nicotinic receptors= cause alertness
Also, pathways for dopamine from ventral tegmental area (also in brainstem)- switching pre-frontal cortex online
Where the spinohypothalamic fibres terminate?
In the hypothalamus- critical for autonomic response to pain.
What is the key pathway for carrying sensed pain?
Lateral spinothalamic tract
How are vibration, light touch, proprioception and pain tested in a clinical setting?
Vibration= tested by a tuning fork
Light touch= cotton wool
Proprioception= joint position sense
Pain= neurotips
Where do the majority of the fibres in the spinothalamic pathway terminate?
85% of the fibres in the spinothalamic pathway terminate in the brainstem, in the reticular activating system- they are known spinoreticular fibres
Where is the superior colliculi?
Two bumps on the back of the brainstem, in a area known the tectum
What is the function of fibres that arrive in the superior colliculi (and how does this relate to pain)?
Part of the orientating response- controls eye movement
In response to pain, there is an orientating reflex where we look at the pain location
What are fibres from the spinothalamic pathway that terminate in the superior colliculi called?
Spinotectal fibres
What does the feeling of pain reflect?
Inflammatory cascade mediators such as protanoids and arachidonic acid
What is the analgesic ladder that is used to treat pain?
Simple analgesics first such as paracetemol
NSAIDs and aspirin
Opioids
What is chronic pain?
Neurogenic (there is a problem with processing pain)
What are some of the drug options used to treat chronic pain?
Gabapentin, pregabalin and duloxetine
Then can consider more general neurone supressor drugs if the above do not work such as anticonvulsants.
What is the reticular activating system used in?
Arousal- 85% of spinothalamic fibres known as spinoreticular fibres terminate here.
What happens in the thalamus after pain stimuli is sensed?
Fibres connecting to the thalamus then connect to a structure called the insula and the anterior singulate cortex then into the pre-frontal cortex. Is a bi-directional loop.
PFC helps to model what is going on
What causes chest pain in heartbreak?
ACC and insula have a sort of somatotopic map of the viscera which can cause chest pain in heartbreak.
What is the reason pain is unpleasant?
Amygdala connections for negative emotion. The reason why pain is unpleasant . Gives us motivation to fix the pain.
What. is the peri-aqueduductal grey and how is it involved in pain?
area of grey matter that sits in the brainstem around the cerebral aqueduct. Important structure that is the ‘volume knob’. Is a tolerance control.
How is the peri-aqueductal grey involved in pain inhibition?
Cells of PAG release serotonin (5-hydroyxtrptamine). 5HT travels in CSF downwards and triggers endogenous opioid release in dorsal horn spinal cord interneuonres
Endogenous opioids reduce incoming pain pathway activity via opioid receptors
What two structures can adjust the periaqueductal grey?
The amygdala and pre-frontal cortex
What happens in pain?
The reticular activating system causes arousal
The superior colliculi moves eyes to look at pain site
There is a hypothalamus controlled autonomic response
There is then connections from the thalamus to insula to amygdala (controls negative emotions) and from the thalamus to ACC to PFC
