Lecture 16: Brain Arousal Systems Flashcards
(33 cards)
What is the difference between, coma, persistent vegetative state and minimally conscious state
Coma = neither awake nor aware
Persistent vegetative state = physiologically identifiable sleep/wake cycle appear, no evidence of awareness
Minimally conscious state = sleep/wake cycles, reproducible evidence of awareness - ability to respond to simple commands (need to respond verbally, not just turn head toward voice), limited or absent communication
What are the levels of consciousness?
Coma -> arousal/wakefulness-> awareness -> alertness
List the basic arousal systems
Excitatory AAs Cholinergic Noradrenergic Serotonergic Dopaminergic
Where does the noradrenergic system arise from?
Locus ceruleus
Where does the serotonergic arousal system arise from?
Raphe nuclei
Where does the dopaminergic arousal system arise from?
Ventral tegmental area
Where does the cholinergic arousal system arise from?
Pedunclopontine tegmental and laterodorsal nuclei
Where does the excitatory AA arousal system arise from?
Reticular activating system and parabrachial nuclei -> both in cerebellum and pons
Where is the reticular activating system?
Located in medulla and midbrain
What does the reticular activating system receive information from?
All ascending sensory tracts
There is sufficient synaptic convergence of input to the neurons of the RAS that modal specificity is lost. What does that mean?
All incoming sensory info converges on the same neurons so the brain only knows something happened but not what happened
**This means the neurons of the RAS respond equally well to multiple sensory modalities
Explain the dorsal pathway of outputs from the reticular activating system
Via the non-specific nuclei of the thalamus, including the intralaminar nucleus of the thalamus -> from there diffuse pathways to all higher brain levels
Explain the ventral pathway of outputs fromthereticular activating system
Bypasses the thalamus via basal forebrainand hypothalamus -> from there, diffuse pathway to all higher levels
Where are the parabrachial nuclei located?
The pons
**The parabrachial nuclei are crucial for arousal/activation
What is the difference between outputs from the reticular activating system and outputs from the parabrachial nuclei?
The outputs are likely exclusively via the ventral pathway
**This is a survival mechanism bc if you lose one system you have the other that does essentially the same thing
What types of inputs are received from the parabrachial nuclei?
Sensory inputs similar to those seen in the reticular activating system -> all/most of the sensory inputs to the body
What is the major NT utilized by both the parabrachial and the RAS neurons?
Glutamate -> for both dorsal and ventral pathways
What is the major NT for the pedunculopontine tegmental and laterodorsal nuclei?
Ach
What pathways do the outputs of the pedunculopontine tegmental and laterodorsal nuclei utilize?
Dorsal and ventral pathways used by the RAS
Outputs from the locus coereuleus are both ascending and descending. THe ascending Pathways use the dorsal and ventral pathways with the RAS. The ascending fibers from this group of cells become the ___________________ bundle
Dorsal noradrenergic bundle
What are the functions of the locus coereuleus noradrenergic system?
Startle and alerting* responses on the EEG
Sleep-wake
Behaviora vigilance*
What are the inputs to the locus coereuleus noradrenergic system?
Paragigantocellularis n (in rostral medulla) -> sensory info
PAG
Higher centers, including cortex
**This info has undergone more neural processing than the sensory inputs received by the EAA/Ach systems
What are the outputs for the serotonergic arousal system?
For arousal, both the dorsal and ventral** paths are used -> there are other outputs related to other functions of the raphe
**Ventral pathway is the predominant pathway here (bypasses thalamus)
What are the functions of the serotonergic arousal system?
Quiet awareness
