1. Medical: the state of being aware and responsive to one's surroundings.
2. A person's awareness or perception of something.
- Involves perception, cognition, action.
What are the levels of consciousness?
How would you define disorders of consciousness, with reference to locked-in syndrome, minimally conscious state, unresponsive wakefulnes syndrome, chronic coma and brain death.
How would levels of concsiousness be identifiable in an PET scan?
What is the most serious common loss of consciousness worldwide?
In the UK, what medical conditions can result in a loss of consciousness?
- Stroke (Haemorrhage, Thrombosis, Embolus)
- Drug Induced (alcohol/other poison/overdose)
- Head Injury
- Raised Intracranial Pressure (tumour/abscess)
- Uraemia, Liver Disease (other metabolic disorders).
Summarise the glasgow coma scale.
In the glasgow coma scale, what is under the category 'Best Eye Resonse'
4. Spontaneous eye opening.
3. Eye opening in response any speech (or shout, not necessarily request to open eyes).
2. Opening in response to pain (to limbs).
1. No response.
In the glasgow coma scale, what is subcategorised as 'Best Verbal Response'
5. Orientated: Patient know who he is, where he is and why, the year, season and month. (Infant: Smiles, orientated to sounds, follow objects, interacts).
4. Confused conversation: Patient responds to questions in a conversational manner but some disorientation and confusion (Infant: Cries but consolable, inappropriate interactions).
3. Inappropriate speech: Random or exclamatory articulated speech, but no conversational exchange. (Infant: Inconsistently inconsolable, moaning).
2. Incomprehensible speech: Moaning but no words. (Infant: Inconsolable, agitated).
1. No verbal response.
In the glasgow coma scale, how would you categorise: 'Best Motor Response'
6. Obeying Command: Patient does simple things you ask. (Infant: moves spontaneously and purposefully).
5. Localising response to pain: Pinch earlobe, put pressure on the patient's finger nail bed with a pencil, supraorbital and sternal pressure. Purposeful movements towards changing painful stimuli is a 'localising' response. (Infant: withdraws from touch).
4. Withdraws to pain: Pulls limb away from painful stimulus. (Infant: withdraws from pain).
3. Abnormal flexor response to pain: Painful stimulus causes abnormal flexion of limbs (decorticate).
2. Extensor posturing to pain: Painful stimulus causes limb extension (adduction, internal rotation of the shoulder, pronation of forearm) (decerebrate).
1. No response to pain.
Summarise the glasgow coma scale.
What are the different thresholds in the glasgow coma scale?
E + V + M = 3 to 15
- 90% less than or equal to 8 are in a coma.
- Greater than 9 = not in a coma.
- 9-11 = moderate severity.
- 12+ = minor injury.
8 is the critical score. More than 50% of those at 8 die after 6 hours.
In summary, if a patient is in a coma:
E = not opening eyes.
V = not uttering understandable words
M = not obeying commands.
How would you diagnose and confirm a death?
- Irreversible loss of the capacity for consciousness combined with irreversible loss of the capacity to breathe.
- The irreversible cessation fo brain stem function equates with the death of the individual.
Define Brain stem death.
NHS Definition: For a diagnosis of a brain stem death to be made:
- A person must be unconscious and fail to respond to outside stimulation.
- A person's heartbeat and breathing can only be maintained using a vertilator.
- There must be clear evidence that serious brain damage has occured and it can't be cured.
What is the criteria for brain stem death?
- Aetiology of irreversible brain damage.
- Patient is deeply comatose, unresponsive, requiring artifical ventilation.
- Not caused by depressant drugs
- Not caused by primary hypothermia
- Not caused by potentially reversible circulatory, metabolic and endocrine disturbances.
- Not caused by potentially reversible causes of apnoea (dependence on the ventilator) such as muscle relaxants and cervical cord injury.
What brain-stem reflexes do you test for in brain death?
- Pupil responses - Shine torch in eyes.
- Corneal reflex - Gently stroke cornea (transparent outer layer of the eye) with tissue or piece of cotton wool.
- Vestibulo-Ocular reflex (VOR) - Insert ice-cold water into each ear, which would usually cause the eyes to move.
- Cranial nerve motor responses - Apply supraorbital pressure to elicit motor response.
- Cough/Gag reflex - Insert catheter down treachea/stimulate posterior pharynx with spatula.
- Respiratory effort - when ventilator is disconnected - 5 mins.
Most of the cues that control the level of activity in the thalamus, neocortex etc. originate in the brainstem.
- This is called the reticular activating system (RAS).
Give more facts about how this system controls concsiousness.
- Made up of complex system of nuclei and tracts - trying to work out what each bit does & how it interacts with it's neighbours is hard.
- There is also the reticuluar formation - A collection of nuclei found throughout the midbrain and extends into the hindbrain (pons & medulla) and the spinal cord.
- Diffuse area, no clear anatomical boundaries, not easily seen on brainstem sections.
- Also called the diffuse modulatory system.
Give the location of the four nuclei of the reticular activating system (RAS).
Give some facts about the locus coeruleus (blue spot)
- Located in pons.
- Sends information to nearly all the CNS.
- Active during arousal, novel stimuli, mediates sympathetic effects of stress.
- Disorders: anxiety, panic, PTSD.
- Hypoactivity associated with depression
- Neurotransmitter: Noradrenaline NA
Explain the Raphe Nuclei of the Reticular Activating System.
- Collection of nuclei in midline in midbrain, pons & medulla.
- Project to large areas of the CNS.
- Cells in rostral parts active during waking state.
- Projections help regulate circadian rhythm, enkephalin release (pain inhibition).
- Disorders: Depression, OCD.
Neurotransmitter: Serotonin (5-HT).
Explain the role of the Ventral Tegmental Area (VTA) or the reticular activating system (RAS).
- Ventral region of midbrain.
- Project mainly to frontal cortex and limbic system.
- Involved in reward circuity of the brain - reinforces pleasurable sensations, motivation & intense emotions.
- Disorders: drug addiction, schizophrenia, Parkinson's disease, attention deficit hyperactivity disorder (ADHD).
- Neurotransmitter: Dopamine (DA).
Explain the role of the Cholinergic nuelci in the reticular activating system.
Basal Forebrain Nuclei (purple)
- Projections to all cortical areas, especially frontal.
Dorsolateral Pontine Nuclei (green).
- Project to basal ganglia, thalamus, hypothalamus, brainstem, cerebellum.
- Active during states of arousal, induce wakefulness and REM sleep.
- Contribute to synaptic plasticity and involved in learning and memory.
- Disorders: Alzheimer's disease, amnesia, dementia.
What is associated with damage to the anterior hypothalamus - ventrolateral preoptic nucleus)?
- GABA mediated
- Associated with insomnia (shorter sleep)
- Damage to the anterior hypthalamus is not the major cause of insomnia).
What is associated with damage to the posterior hypothalamus? (tuberomammilary nucleus)
- Associated with sleeping sickness (longer sleep)
- Stimulation of this area releases Histamine
- Histamine is an arousing neuromodulator.
Give an overview of the role of neurotransmitters in the brain in relation to the RAS function.
How are the reward and wakefulness pathways interlinked?
What receptors are involved in cortical arousal?
Explain the role of the ascending reticular activating system
Awake: cholinergic fibres increase firing.
Alseep: cholinergic fibres decrease firing.
Explain the differences in the sleep-wake cycle.
How are Sleep and EEG oscillations generated?
They are generated by the interaction between three types of neurons.
- Thalamocortical (in thalamus).
- Reticular (in reticular nucleus).
- Corticothalamic (in cerebral cortex).
What are the sleep stages and characteristics of each stage?
What are the two main types of sleep?
1. Synchronised or NREM (Non-REM) sleep.
- EEG waves are slow and synchronised.
- Dominated by low frequency activity (e.g delta waves <4Hz)
2. Desynchronised or REM sleep
- REM = rapid eye movement.
- Every 90-120 minutes.
- High frequency activity in EEG (like waking state).
- Also called paradoxical sleep.
- Abolition of muscle tone
- Associated with dreams.
What are the common/rare disorders of sleep?
- Psychiatric conditions including anxiety
- Indicators of other conditions:
- Orthopnea (shortness of breath)
- Enuresis (bladder control)
- Epilepsy (neuronal siezures).
- Narcolepsy - spontaneous transition from wakefulness to REM sleep, caused by mutation of orexin receptor gene.
What are the consequences of sleep[ deprivation?
- Slower reflexes
- Memory disorders
- Muscle fatigue
- Mood Swings
- Aggressive Behaviour
Long Term (chronic)
- High Blood Pressure
Summarise the circadian rhythm.
- Neurons in the retina project to the Suprachiasmatic Nucleus (SCN) of the hypothalamus.
- SCN inntervates multiple nearby structures setting up a 'biological clock'
- SCN secretes neuropteptides vasopressin (to local brain areas only)
- Indirectly modules the pineal gland which secretes melatonin, a sleep promoting neurohormone.