The Reticular Formation & Consciousness Flashcards
Introduce the reticular activating nuclei of the brain stem in relation to states of arousal including sleep
Formed by projections of RF
Raise level of consciousness
Inhibited by hypothalamic sleep centres, alcohol, drugs
List some brainstem neurotransmitters and relate these to the neuropharmacology of some disorders
Noradrenaline, serotonin - depression
ACh - Alzheimer’s
Dopamine - Parkinson’s, schizophrenia
Describe the origin and evaluation of the EEG in the wakeful state and in sleep
EEG - algebraic sum of the electrical activity of neurones
Beta waves - awake, eyes open
Alpha waves - awake, quiet, eyes shut
Theta waves - children, concentrating/meditating adults
Delta waves - deep sleep, serious brain conditions
Define the terms ‘arousal’, ‘consciousness’ and ‘coma’
Arousal - the emotional state associated with some kind of goal or avoidance of something noxious
Consciousness - requires adequate function of both the cerebral cortex and reticular activating system (awareness of external world and internal state)
E.g. Locked-in syndrome = intact cortex, PVS = intact brainstem, brain dead = no activity in cortex or brainstem
Coma - state of unconsciousness from which the person cannot be roused using pain, sound, light. Patient does not initiate any voluntary movement
Describe some functions of the reticular formation
Sleep regulation Motor control Cardio/resp control Autonomic functions Motivation, reward
Contrast non-REM and REM sleep states
Non-REM - slow wave, active body, inactive brain, sleepwalking
REM - active brain, inactive body, dreaming, difficult to disturb (strongly inhibited thalamus)
Name some sleep disorders
Insomnia - anxiety –> overacting cortex –> increased activation of RS
Parasomnia - sleepwalking, paralysis
Narcolepsy - decreased orexinergic neurones/mutation in gene –> decreased activation of RS (spontaneous sleep)
Sleep apnoea - increased fat around neck –> compresses airway –> sensory stimulus (hypoxia)
Outline ‘AVPU’ scale of assessment of consciousness
Alert
Verbal
Painful
Unconscious
Outline the ‘Glasgow Coma Scale’ of assessment of consciousness
Highest score = 15 Lowest score = 3 Eye opening (/4) - spontaneously, to speech, to pain, none Verbal response (/5) - orientated, confused, inappropriate words, incomprehensible, none Motor response (/6) - obeys commands, localise pain, flexion to pain, flexion/withdrawal, extension to pain, none
Describe the initial assessment of level of consciousness
Airway - jaw thrust, suction, nasopharyngeal airway, high flow oxygen
Breathing - mask misting, chest movement, indicator mask, intubation (endotrachial tube)
Circulation - capillary return, palpable pulse, movement, breathing effort
Disability - AVPU, GCS
Name the immediate treatment for hypoxia, hypoglycaemia, seizures and opiate overdose
Hypoxia - high flow oxygen
Hypoglycaemia - IV glucose
Seizures - IV lorazepam
Opiate OD - IV+IM naloxone
Give three mechanisms of altered consciousness
Affecting cortical function e.g. metabolic disturbance
Pressure effect on brainstem inhibiting RAS e.g. high ICP causing herniation
Direct lesion within brainstem damaging RAS e.g. brainstem infarction
List different types of brain herniation
Subfalcine - cingulate gyrus –> falx cerebri
Central
Uncal transtentorial - temporal lobe, oculomotor palsy
Tonsillar - cerebellum –> foramen magnum
*coning = hypotensive, bradycardia
Describe structures involved in the reticular activating system
Sensory –> RF –> thalamus (glutamate)/hypothalamus (histamine)/basal forebrain nucleus (ACh)
*+ve feedback loop between RF and cortex ensures constant consciousness
Describe how the RAS enables sleep
Decreased +ve stimulus and cortical activation = sleep
Stay still - inhibits sensory system
Eyes closed - interneurone stimulates orexin neurone
Slow mind - inhibits activity from cortex
*REM sleep = stimulate thalamus, strongly in deep sleep
