Phys - Brain Arousal Systems Flashcards
describe coma
neither awake or aware
- no sleep/wake cycles
- EEG waves normally abnormal
describe persistent vegetative state
physiologically identifiable sleep/wake cycles
- no evidence of awareness
- EEG may or may not be abnormal
(the “arousal/wakefulness” level of consciousness)
describe minimally conscious state
pt has sleep/wake cycles
- reproducible evidence of awareness; ability to respond to simple commands
- limited or absent communication
are disruptions of consciousness usually from damage to cerebral cortex?
it can be, but the damage would have to be massive and bilateral
- more often from smaller lesions in brainstem, midbrain, or hypothalamus
what is the reticular activation system (RAS)?
- what tracts use it?
a type of arousal system that uses EAA
- all ascending sensory tracts send info to the RAS
where is the RAS located
mid-ventral portion of medulla and midbrain
why does the RAS system lose modal specificity?
there is sufficient synaptic convergence of input to the neurons of RAS that it loses specificity
compare the two pathways of the RAS
dorsal: synapses in intralaminar nucleus of thalamus
ventral: goes through basal forebrain and hypothalamus but NOT the thalamus
where are the parabrachial nuclei located
in the pons
what inputs go to the parabrachial nuclei?
similar to RAS; all/most of the sensory inputs in the body
what pathway do the parabrachial nuclei use
ventral pathway (bypass the thalamus)
where in the cortex do the parabrachial nuclei innervate?
diffuse innervation of the entire cortex
what is the major NT utilized by both parabrachial nuclei and RAS
EAA/glutamate
what other NTs does the RAS release?
GABA
Ach
why do the PPT/LDT nuclei lose modal specificity?
they receive so much input that specificity is lost
