Consciousness Flashcards
What is the definition of consciousness?
Processes that enable us to experience the world around us
What is the distinction between levels and contents of consciousness?
Levels- alertness
Contents- subjective experience
What does alertness involve?
Reticular formation- regulates many vital functions
What does the reticular formation project to and what does this allow?
It projects to the thalamus and the cortex, allowing it to control whether or not sensory signals reach cortical sites of conscious awareness such as posterior parietal cortex
What is the reticular formation?
Polysynaptic network in the core of the midbrain, pons and upper medulla that contains noradrenaline and cholinergic neurones which project to receptors in cortex and boost level of activity in cerebral cortex via the thalamus- vital to maintaining alertness
What are the other functions of the RF apart from control of alertness?
Centres which regulate body systems such as cardiovascular, respiratory, bladder and motor patterns
Where does the RF receive information from?
All sensory pathways: Touch and pain from ascending tracts Vestibular from medial vestibular nucleus Auditory from inferior colliculus Visual from superior colliculus Olfactory via medial forebrain bundle
Via what systems and projections does the RF modulate cerebral activity?
The nucleus coeruleus consists of norepinephrinergic neurones which project directly to cerebral cortex
Ventral tegmental nucleus consists of dopaminergic neurones which project directly to cortex
Cholinergic neurones which project to the thalamus
Raphe nuclei in midline which are main source of serotonergic projections to brain and spinal cord
Which type of neurones are most important for regulating level of arousal?
Cholinergic- they increase level of activity in cerebral cortex via thalamus
By what 3 mechanisms do cholinergic neurones increase activity in cerebral cortex via the thalamus?
Excitation of individual thalamic relay nuclei leading to activation of cortex
Projections to intralaminar nuclei which in turn project to all areas of cortex
Projections to reticular nucleus which regulates flow of info from other thalamic nuclei to cortex
How is level of arousal monitored?
EEG rhythms (electrical activity of neurones to assess alertness and cognitive functions):
Delta waves (<4Hz)- during sleep
Theta (4-8Hz)- drowsiness
Alpha (8-13Hz)- Subject relaxed with closed eyes
Beta (12-30Hz)- Mental activity and attention
What is a contusion?
Bruise that leads to localised bleeding within the brain
What is concussion?
Diffuse, widespread, homogenous impairment of brain tissue due to brain trauma
What are the three criteria that the Glasgow Coma Scale is based on?
Eye opening + Verbal + Motor
What do total GCS score indicate?
GCS < 5: 80% die or remain vegetative
GCS>11: 90% complete recovery
