brain arousal Flashcards
what are the two characteristics of persistent vegetative state
sleep/wake cycles
no evidence of awareness
what are the characteristics of a minimally conscious state
sleep/wake cycles
ability to respond to simple commands
limited/absent communication
what kind of injury most commonly causes disruption of conciousness
small lesions to the brainstem, midbrain or hypothalamus
will a patient in a coma or persistent vegetative state has eye/head motions?
YES, reflexes
what system releases excitatory amino acids?
reticular activating system
how does the dorsal pathway of the reticular activating system excite the cortex
via nuclei of the thalamus (INTRALAMINAR NUCLEUS OF THE THALAMUS) => diffuse pathway to higher levels
how does the ventral pathway of the reticular activating system excite the cortex
via basal forebrain and hypothalamus
what do the parabrachial nuclei do and why
release EAAs for arousal
do the parabrachial nuclei excite the cortex via the dorsal or ventral pathway?
ventral pathway only
do the peduncopontine tegmental and laterodorsal (PPT/LDT) nuclei excite the cortex via the dorsal or ventral pathway?
BOTH
what is the major NT of the PPT/LDT nuclei
ACh
does damage to the PPT/LDT nuclei cause coma
no, it causes severe cognitive deficits and slowing of cortical processes
how would a patient with RAS, PPT/LDT and parabrachial nuclei functioning be characterized
persistent vegetative state (awake, but not alert or aware)
what are the two inputs to the locus coereulus?
paragigantocellularis n
periaqueductal grey
what do the ascending fibers from the locus coereulus become?
the dorsal noradrenergic bundle
does the locus coereulus excite the cortex via the dorsal or ventral pathway?
BOTH
what is the main function of the locus coereulus system
startling and alerting- pt aware of specific event
what is the source of serotonergic input to the cortex?
raphe nuclei
what is the source of noradrenergic input to the cortex?
locus coereulus
what is the source of cholinergic input to the cortex?
PPT/LDT nuclei
what is the function of serotonergic activation of the cortex?
quiet awareness
what structure facilitates quiet awareness?
raphe nuclei
does the raphe nuclei excite the cortex via the dorsal or ventral pathway?
BOTH
if the noradrenergic and serotonergic pathways are functioning in a patient, how are they characterized?
awake and aware, NOT alert
what kind of input facilitates alertness
dopaminergic
what structure provides dopaminergic input to the cortex
ventral tegmental area (VTA)
what input to the cortex facilitates cognitive function, motor activity and emotion
dopaminergic
what is the route of axons on the dorsal pathway to the cortex
arousal center => thalamus (synapse) => cortex
what is the route of axons on the ventral pathway to the cortex
arousal center => cortex => synapse on cortical neurons
what creates the oscillations on EEG
intracortical neurons which interact with thalamic projections and release GABA
in a persistent vegetative state, are cortical neurons hypo- or hyper polarized?
hyperpolarized 10-20 mV
what causes memory impairment and slowing of mental processes in alzheimer’s dz
destruction to cholinergic systems
during REM sleep, what physiologic changes cuts the cortex off from excitation?
hyperpolarization of the thalamocortical neurons
