7. Brain Arousal Systems Flashcards
(42 cards)
Consciousness is recognized as having two parts, what are they and what do they mean?
arousal (being awake)
awareness (conscious processing of inputs)
Coma means one is neither awake nor aware (conscious) which a persistent vegetative state means?
physiologically identifiable sleep/wake cycles appear
no evidence of awareness
What is classified as having sleep/wake cycles, ability to respond to simple commands, and limited/absent communication?
minimally conscious state
What is the tree from least to most conscious? 4
coma to arousal/wakefulness to awareness to alertness
What kind of damage must occur in order for someone to be in a comatose state due to a cortical issue?
massive and bilateral cerebral cortex damage
More often, disruptions of consciousness result from smaller lesions in which locations? as compared to the cortex
Brainstem
midbrain
hypothalamus
Arousal and awareness require activation of the cortex but the cortex has no intrinsic mechanism for activation. so what provides the activation?
sub-cortical structures
Which of the following can be seen with a Coma? Eye/head movement Sleep/wake cycle awareness verbal response
Eye/head movement: Sometimes
Sleep/wake cycle: no
awareness: no
verbal response: no
What can be seen with Persistent vegetative state? Eye/head movement: Sleep/wake cycle: awareness: verbal response:
Eye/head movement: yes
Sleep/wake cycle: yes
awareness: no
verbal response: no
What can be seen with minimally conscious state? Eye/head movement: Sleep/wake cycle: awareness: verbal response:
Eye/head movement: yes
Sleep/wake cycle: yes
awareness: maybe
verbal response: maybe
What can be seen with aware/alert state? Eye/head movement: Sleep/wake cycle: awareness: verbal response:
Eye/head movement: yes
Sleep/wake cycle: yes
awareness: yes
verbal response: yes
EAA arousal system has a reticular activating system (RAS), which are loose connections ofneurons and fiber tracts which occupy what region of the brain?
midventral portion of medulla and midbrain
The RAS takes input from all ascending sensory tracts as well as what three?
trigeminal
auditory
visual
There are so many synaptic convergence of input to the RAS that what is lost?
modal specificity is lost
Modal specificity can be best described as?
the brain ONLY knows something happened, not exactly WHAT happened
The output of information from the EAA RAS has two pathways, one is the dorsal pathway via the non-specific nuclei of the thalamus, including?
intralaminar nucleus of the thalamus, which diffuses to all high levels
The second pathway for output of info from the RAS in the midventral portion of medulla and midbrain is the ventral pathway via?
basal forebrain and hypothalamus
The parabrachial nuclei (medial lateral and intermediate) is located in the pons and are crucial for arousal /activation. What is the one BIG difference between parabrachial nuclei and RAS?
outputs are exclusively via ventral pathway through basal forebrain and hypothalamus
What is the major NT utilized by both the parabrachial and RAS neurons?
EAA/Glutamate (dorsal and ventral pathways)
EAA provides baseline excitation crucial to cortical activity (via dorsal and ventral pathways). The next arousal system is the cholinergic system which consists of which nuclei?
pedunculopontine tegmental and laterodorsal nuceli (PPT/LDT)
Like RAS, PPT/LDT receives alot of info so modality is lost and outputs are via dorsal/ventral pathways but what is different?
NT is acetylcholine
Damage to the PPN/LDT doesnt cause a coma but does produce what?
severe cognitive deficits which slow cortical processes (in pons)
What will get you from coma to arousal/wakefulness?
EAA (RAS/parabrachial) and Cholinergic Systems
To move from arousal/wakefulness to awareness you need more input via the noradrenergic system located?
locus ceruleus
