Mechanisms of Arousal: Brain Arousal Systems Flashcards
What are the two parts of consciousness
arousal and awareness
Coma
neither awake nor aware
persistent vegetative state
physiologically identificable sleep/wake cycles, no awareness
minimally conscious state
sleep/wake cycles, reproducible evidence of awareness, limited/absent communication
Comatose state results from damage to the cerebral cortex in what circumstance
damage must be large and bilateral
What is a common cause of consciousness
smaller lesion in brainstem, mid brain or hypothalamus
What is required for both arousal and awareness
activation of the cortex
what is present in a coma
eye/head motions, that are intermittent
what is present in a persistent vegetative state
eye/head movements, sleep/wake cycles
What is present in minimally conscious individual
eye/head motions; sleep/wake cycle; awareness and verbal responses are intermittent
aware/alert individual has
eye/head motions; sleep/wake cycles; awareness and verbal responses
What are the arousal systems/compounds
EAA cholinergic noradrenergic serotonergic dopaminergic
Where are EAA arousal systems located
reticular activating system and parabrachial nuclei
Where are cholinergic arousal systems located
pedunculopontine tegmental and laterodorsal nuclei (PPT/LDT)
Where are noradrenergic arousal system located
locus ceruleus
Where are serotonergic arousal systems located
raphe nuclei
where are dopaminergic arousal systems located
ventral tegmental area
What are the two pathways of the RAS pathway
Dorsal and ventral
What is the path of the dorsal pathway
nonspecific nuclei of thalamus, including intralaminar nucleus. Goes from there to diffuse pathway to higher levels.
What is the path of the ventral pathway
Basal forebrain and hypothalamus, diffuse pathway to all higher levels after that.
Where are the parabrachial nuclei located
In the pons
Function of parabrachial nuclei
crucial for arousal/activation
What is the path the parachial nuclei take
Exclusively ventral pathway with extensive diffuse innervation of the entire cortex
What are the neurotransmitters used by both parabrachial and RAS neurons
EAA/Glu (dorsal and ventral pathways)
What other products are released by interneurons and neuronal population in the RAS?
Interneurons=GABA
Neuronal population= ACh
What does EAA system provide
Baseline excitation crucial for cortical activity
What path does PPT/LDT take
both dorsal and ventral
What does cholinergic system provide for cortical activity
baseline excitation crucial to cortical activity
What is cholinergic inputs from pons associated with
arousal and awareness
Does PPN/DLT cause coma
not necessarily, does cause severe cognitive deficits from slowing cortical processes
What neurotransmitters lead to arousal/wakefulness
EAA/Ach
What are the outputs from teh Locus coereuleus
ascending and descending
What pathways does the ascending output of the locus coereuleus follow
dorsal and ventral with RAS
What do the ascending fibers in the L.C. become
dorsal noradrenergic bundle
Function of LC. NA system
startle and alerting responses on EEG
sleep/wake
behavioral vigilance
What are the inputs of the raphe nuclei
sensory from SC (fine proprioception, trigeminal and PAG)
What are the outputs for arousal of the raphe nuclei
dorsal and ventral paths
Function of serotonergic
quiet awareness, mood and affect, modulation of pain
What neurotransmitters lead to awareness
NE/5HT
What provides a dopaminergic input
VTA along with substantia nigra
Functions of VTA
cognitive functions, motor activity, emotion
What neurotransmitters lead to alertness
DA
What is the pathway for the dorsal pathway
arousal systems send axons to thalamus, then synapse and axons from thalamus then go to cortex. Synapse on cortical neurons.
Where does the dorsal pathway neurons synapse
non-specific nuclei of the thalamus. Difuse projection to the entire cortex, use EAA as neurotransmitter
What do the Thalamic arousal system neurons interact with
with EAA and neurons, interact with a series of intracortical neurons release GABA.
What parts of the brain show neuron loss in a persistent vegetative state
rostral regions of pons, midbrain, thalamus
In Alzheimer’s disease, what is hurt?
cholinergic systems, memory formation is profoundly impaired.
What systems move us from being awake to more generally aware
noradrenergic and serotonergic
What medicine has helped people in a persistent vegetative state
levodopa
What does dopaminergic system do
adds to awareness, focused on novel stimuli
What happens during sleep in the thalamic arousal system?
thalamocortical neurons are hyperpolarized, show occasional burst, cuts cortex off from excitatory influence during the deepest levels of sleep
