Brain Arousal Karius T#2 Flashcards
What two parts make up consciousness?
- Arousal (being awake)
- Awareness
What is a coma?
person is neither awake or aware with absence of sleep and wake cycles
What is a persistance vegetative state?
- physiologically identifiable sleep wake cycles-you see REM
- NO evidence of awareness
What is a minimally conscious state?
- sleep wake cycles
- reproducible evidence of awareness-can respond to simple commands
- limited or absent communication
In a persistance vegetative state damage to what section of the brain is more common?
small lesions in:
- brainstem
- midbrain
- hypothalamus
also shown that cortical neurons are up to 30 mV below threshold—very hyperpolarized
Describe the EAA, what does it mean by saying this is the most basic?
It works on the Reticular activating system and the parabrachial nuclei in the pons.
Has to be present and functional to move from comatose to persistant vegetitave state
What is the cholinergic arousal system?
Pedunculopontine tegmental and laterodorsal nuclei, basic (EAA) needed
What is the significance of the noradrenergic, serotonergic and dopaminergic arousal systems?
They lead to greater levels of consciousness
- noradrenergic: Locus ceruleus
- Serotonergic: raphae nuclei
- Dopaminergic: ventral tegmental area
Where is the EAA located>
Mid ventral portion of the medulla and midbrain, it is a loose collection of neurons and fiber tracts
What is the does the EAA recieve?
Recieves ALL ascending sensory tracts also recieves trigeminal, ,auditory, and visual information
Whta does it mean in the RAS for modal specificity to be lost?
All info convertges on the same neurons so the brain only knows that something happened, but it doesn’t recognize the difference between the visual, auditory trigeminal or sensory tracts.
How does information get from the RAS to the cortex?
- Dorsal pathway: RAS sends axon to non specific nuclei of the thalamus using excitatotry aa which then sends an axon to cortex
- Ventral pathway:RAS sends axon straight to cortex, bypassing thalamus, using excitatory aa
How do you get from comatose to a persistant vegetattive state?
By having an acitive EAA therefore RAS and pararbrachial nuclei
Where is wthe parabrachial nuclei located and what system is it a part of?
- Located in the pons
- Part of EAA
- Recieves almost all of the same sensory inputs that the RAS receives
Outputs from the parabrachial nuclei?
Exclusively ventral pathway, so it bypasses the thalamus and sends axons dierectly to the cortex and uses excitatory aa such as glutamate
What two parts make up the cholinergic arousal system, what is the NT, what paths?
- Pedunculopontine tegmental and laterodorsal nuclei, which recieve so much input same as EAA that they lose modal input. They only know that something happend.
- uses dorsal and ventral outputs, but uses Ach!
How do you move from persistant vegetative state to awareness
- Needs EAA and Cholinergic to be vegetative
- To move to awareness you need noradrenergic also
Activity in cholinergic inputs from the pons is associated with ____ and ___.
Where is the Noradrenergic system located?
- Locus Cereuleus which recieves sensory from a lot of places
- However, it is processed information, not like EAA/Chol.:
- Paragigantocellularis
- Periaqueductal grey
- Higher centers including the cortex
How do outputs from the locus cereuleus send info to cortex?
- dorsal path
- ventral path
What are the functions of the LC NA system?
- Startle and alerting responses on the EEG
- sleep-wake
- produce behavioural vigilance
Where does the serotonergic input come from?
Raphe Nuclei located at the midline
What are the inputs from the serotonergic system?
- Sensory from spinal cord- very specific information
What are the outputs for the serotonergic system?
- Dorsal and ventral pathways
- Other outputs related to function
What function does serotonin give?
- Quiet awareness
- Mood and affect modulation of pain are non RAS activities
To move from general awareness to actual alertness what is needed
Dopaminergic system from the ventral tegmental area
The ventral tegmental area provides dopaminergic input that is important for?
- Cognitive functions
- motor activity
- emotion
What are the neurons from the thalamus to cortex called?
Thalamocortical neurons, these are present in the dorsal pathway
Where do the synapses occur in the dorsal pathway?
- Non-specific nuclei of the thalamus
What do the thalamocortical neurons with EAA input synapse on in the cortex?
GABAergic neurons which cause alternating waves of excitation due to the EAA and inhibition due to the GABA realeased. This leads to waves being recorded on the EEG showing sleep wake cycles
In a persistant vegetative state what happens to rostral regions of pons idbrain and thalamus show?
In alzheimer’s disease what system is hit hard?
The cholinergic systems. Mental processses slow dramatically and memory formation is imparied in absence of excitation
The noraderenergic and serotonergic systems move from awake to generally aware of information.
What does an alerting response in an EEG indicate?
That the cortex is looking for sensory input
How do thalamocortical neurons show action potentials?
During sleep the neurons are hyperpolarized, which cuts the cotrtex off from the excitatory influence during deepest levels of sleep
