The Reticular Formation Flashcards
Define consciousness
Something to do with awareness of both external world and internal states
Define arousal
Emotional state associated with some kind of goal or avoidance of something noxious
What do we need for consciousness?
Functioning cerebral cortex
Functioning reticular formation
What is the reticular formation?
Population of specialised interneurones in the brainstem
Numerous inputs - regulate the levels of arousal = somatosensory system and cortex
Multiple outputs – thalamus, hypothalamus, basal forebrain nuclei, spinal cord
Outline the maintenance of consciousness
RF inputs = descending excitatory cortex stimulation, sensory inputs
RF outputs = 1) ACh to thalamus – gutamate to cortex, 2) ACh to hypothalamus – histamine to cortex, 3) ACh to basal forebrain nuclei – Ach to cortex
What is the role of the basal forebrain nuclei?
Receive cholinergic inputs from the reticular formation
What is GCS?
Glasgow coma score
Assess eye opening, motor response, verbal response
Lower the score the more severe the damage
What is an EEG – electroencephalogram?
Measures the combined activity of thousands of neurones in a given part of the cortex to a very high temporal resolution
Sleep includes what stages?
REM – rapid eye movements
Stage 1
Stage 2
Stage 3
Stage 4
Outline an EEG when awake with eyes open
Beta waves
50 Hz
Irregular = processing complex input
Outline an EEG when awake with eyes closed
Alpha waves
10Hz
Synchronised = if you deprive the brain of input it will tend to go into synchrony
Outline the features of Stage 1 sleep
Background of alpha waves with occasional theta waves
5 Hz
What are the characteristics of stages 2/3 sleep?
Background of theta waves with occasional sleep spindles and K-complex
What do sleep spindles represent?
Last attempt of the thalamus trying to wave you up
What is a K-complex?
Taken away all the inputs to the cortex and we start to see its intrinsic rate
Describe how stage 4 sleep appears on an EEG
Dominated by intrinsic rate of the cortex = delta waves
1 Hz
Synchronous
Describe REM sleep and how it appears on EEG
Beta waves
Dream state
Its as if you are awake as the cortex is suppling visual info
Initiated by groups of neurones in the pons
Very diff to awake someone from REM sleep = strong inhibition of the thalamus
Paralysed due to LMN inhibition by glycine
Outline the neural mechanism of sleep?
Removing as many inputs into the reticular formation as possible = deactivating
What are the functions of sleep?
Enigmatic
Energy conservation and bodily repair
Memory consolidation
Clearance of extracellular debris
What is narcolepsy?
Rare
Problems in neurotransmission = problem maintaining wakefulness
Outline sleep apnoea
Compression of airway by soft tissue = constantly being woken by hypoxia
Name some disorders of consciousness
Brain death = widespread cortical and brainstem damage
Coma = widespread brainstem and cortical damage, EEG patterns detectable, unarousable, unresponsive, no sleep-wake cycle
PVS = widespread cortical damage, EEG patterns detectable, spontaneous eye opening, sleep-wake cycle detectable
Locked in syndrome = basilar/pontine A occlusion, eye movements, somatic functions from pons down lost
