12) Reticular Formation and Consciousness Flashcards
What is arousal?
Emotional state associated with some kind of goal or avoidance of something noxious
What is consciousness?
Awareness of both external world and internal states
What is the reticular formation?
Diffuse population of specialised interneurones in brainstem
What are the outputs of the reticular formation?
Thalamus
Hypothalamus
Basal forebrain nuclei
Spinal cord
What are the components of the Glasgow Coma Scale?
Eye opening (1-4) Motor response (1-6) Verbal response (1-5)
What does an EEG measure?
Combined activity of neurones in a given part of the cortex, high temporal resolution
What are the 6 stages of sleep?
Awake
Stages 1-4
R.E.M. sleep
Describe an awake EEG:
Irregular, beta waves, 50Hz
Describe a drowsy EEG:
Alpha waves, 10Hz, amplitude increasing
Describe a stage 1 sleep EEG:
Background of alpha waves with slow waves (theta waves, 5Hz)
Describe a stage 2/3 sleep EEG:
Background of theta waves with occasional bursts of activity and big waves (K complexes)
Describe a stage 4 sleep EEG:
Delta waves, 1Hz, cortex acting independently of RF
Describe a REM sleep EEG:
Sawtooth waves (like beta waves)
What is the mechanism behind sleep?
Deactivating the reticular activating system and inhibiting the thalamus - decreased cortical activity
What initiates REM sleep?
Group of neurones in the pons
Why is muscle tone in most of the body lost during REM sleep?
Descending inhibition of LMNs by glycinergic fibres arising from reticular formation and running down reticulospinal tracts
What are some autonomic effects of REM sleep?
Penile erection
Loss of thermo-regulation
What are the functions of sleep?
Bodily repair
Memory consolidation
Clearance of extra-cellular debris
What are some disorders of sleep?
Insomnia
Narcolepsy: excessive sleepiness triggered by extreme emotion
Sleep apnoea
What is brain death and how does it appear on EEG?
Widespread cortical and brainstem damage, flat EEG
What is a coma and how does it appear on EEG?
Widespread brainstem and cortical damage with various EEG patterns detectable, unarousable and unresponsive to stimuli
What is a persistent vegetive state and how does it appear on EEG?
Widespread cortical damage with various EEG patterns Spontaneous eye opening and can localise to stimuli by brainstem reflex
What is locked in syndrome?
Basilar/pontine artery occlusion
Eye movements preserved but all other somatic functions lost from pons down
What are sleep spindles (stage 2/3 sleep)?
Thalamic activity to wake the cortex
