Karius Brain Arousal Flashcards
Definition of arousal
Being awake
Definition of awareness
Conscious processing of inputs
Coma description
Neither awake nor aware. Don’t see reproducible sleep and wake cycles
Persistent vegetative state characteristics
Has sleep/wake cycles but no evidence of awareness
have reflexes ex. If they hear a sound they will move head of if you put something in their hand they will grasp it but that’s just survival mechanism not awareness
Minimally conscious state definition
Clear periods of sleep/wake cycles, reproducible awareness (ability to respond to command), but are limited or absent in communication
Timeline of Consciousness
Coma –>Arousal/Wakefulness–> Awareness–> Alertness
Misconception about comatose state
That it results from cerebral cortices damage (which is true) but the damage must be massive
How does disruption of consciousness occur
Small lesions in the brain from brainstem, midbrain, hypothalamus (central area)
What happens if there is damage of the very lower brainstem
Disrupt breathing and cardiac systems
*not viable living condition
Role of brainstem and cortex in consciousness
Brainstem regions are critical for arousing the cortex
Can the cortex initiate arousal on it’s own?
No, it needs input from the brainstem for activation
What are the 5 arousal systems needed for full consciousness
EAA, Cholinergic, Noradrenergic, Serotonergic, Dopaminergic
Components of the EAA arousal system?
Reticular activating syste and parabrachial nuclei
Where is the EAA arousal system located
“Mid-ventral portion”- Pons and upper medulla
What is the RAS system
Loose collection of neurons and fibers in the EAA
Inputs to RAS
All ascending sensory tracts, trigeminal, auditory, visual
Where do all sensory inputs converge in RAS
On post-synaptic cell of RAS
What happens if there is sufficient synaptic convergence on the RAS
Modal specificity is lost
Modal Specificity Loss
Refers to different senses but not being able to identify those sense
Ex. Knowing that something landed on you but don’t know what
Two pathways of the RAS system
Dorsal pathway and ventral pathway
How is the dorsal pathway sent out (location)
Via non-specific nuclei of thalamus including intra laminar nucleus of the thalamus
Where does the dorsal pathway diffuse to?
All higher pathway levels (all over the cortex)
How is the ventral pathway sent out?
Via basal forebrain and hypothalamus
Where does the ventral pathway diffuse to?
All higher levels BUT bypasses the thalamus
