Brain Arousal Systems Flashcards
What are the 2 parts to consciousness?
Arousal and awareness
Neither awake or aware and no sleep cycles
Coma
No evidence of awareness and physiologically sensed sleep cycles
Persistent vegetative state
Ability to respond to simple commands and has wake and sleep cycles
Minimally conscious state
What is the order of things from coma to alertness?
Coma
Arousal
Awareness
Alertness
What region of the brain is critical for arousing and activating the cortex?
Brainstem
Can patients in a coma have eye/head movements?
Occasionally
What are the arousal systems?
EAA, cholinergic, noradrenergic, serotonergic, dopaminergic
What are the 2 parts to the EAA arousal system?
Reticular Activating System (RAS) and Parabrachial nuclei
What arousal systems MUST be present to move from a coma to a persistent vegetative state?
EAA - Reticular Activating System and Parabrachial nuclei
What can aid the EAA in moving a pt from a coma to the persistent vegetative state but cannot excite the cortex enough on its own?
Cholinergic arousal system
Once the EAA and even the Cholinergic arousal systems are active, what arousal systems move you more and more towards consciousness?
Noradrenergic, Serotonergic, and Dopaminergic
If all arousal systems are active and functioning correctly what is the result?
Fully functional human
Describe the Dorsal pathway?
Neurons synapse at the thalamus first
Then Neurons from there are sent to the cortex to synapse
What are the neurons that travel from the thalamus to the cortex called?
Thalamo-cortical neurons
What do thalamo-cortical neurons release, regardless of what synapsed at them?
EAA
Describe the Ventral pathway?
Neurons go straight to the cortex to synapse
What do neurons that travel using the ventral pathway release at the synapse?
Whatever they were carrying - (i.e. EAA, Ach, NE, 5HT..)
Where is the Reticular Activating system (RAS) located?
Midbrain and medulla
What does the RAS system receive?
ALL ascending sensory tracts, trigeminal, auditory and visual
What pathways does the RAS system use?
Dorsal and ventral
What does the RAS system release the the synapses?
EAA
Where is the Parabrachial nuclei located?
Pons
What does the parabrachial nuclei receive?
ALL sensory inputs from body
What pathways does the parabrachial nuclei use?
ONLY the Ventral pathway
What does the parabrachial nuclei release at the synapse?
EAA
Where is the cholinergic arousal system located?
Pons
What are the 2 nuclei within the cholinergic system?
Pedunculopontine tegmental (PPT) and Laterodorsal (LDT)
What pathways does the cholinergic system use?
BOTH the dorsal and ventral pathways
What NT is released from the cholinergic system synapses?
ACETYLCHOLINE
What does damage to the cholinergic system produce?
Will NOT result in a coma; but will result in progressively decreasing cortical processes and severe cognitive deficits
Where is norepinephrine located?
Locus Ceruleus (in pons)
What does the norepinephrine arousal system receive?
Sensory information that has already underdone some neural processing = more specific info
What pathways for output does the norepinephrine system use?
BOTH dorsal and ventral pathways
What does the norepinephrine system do?
Responsible for producing the startle/alertness response on an EEG
Where is the serotonergic arousal system located?
Raphe nuclei
What does the serotonergic system receive?
Sensory inputs from fine proprioception and trigeminal
What pathways does the serotonergic system use?
BOTH dorsal and ventral pathways
What does the serotonergic pathway do?
Contributes to a quiet awareness
Where is the dopaminergic arousal system located?
Ventral tegmental area
Describe how the EEG waves arise using the dorsal pathway?
- Thalamo-cortical neurons can synapse on to -intracortical neurons
- Intracortical neurons release GABA
- GABA is an inhibitory AA
- -First: excitation; Next: inhibtion = AP then no AP!
What is the non-specific nuclei of the thalamus where dorsal pathway neurons can synapse called?
Intralaminar
During sleep, what happens to thalamo-cortical neurons?
They are hyperpolarized which cuts cortex off from excitatory influence during sleep!
What is needed to move from a coma to an arousal/wakeful state?
EAA / Ach - but mostly EAA
What is needed to move from an arousal/wakeful state to a state of awareness?
NE and 5HT
What is needed to move from a state of awareness to a state of alertness?
Dopamine
Is the information that is relayed to the RAS, parabrachial nuclei or cholinergic systems specific?
NO; just know that something is happening
