Mechanisms of Arousal: Brain arousal systems

Question 1

When an individual is in a Coma: what are they considered

Answer 1

neither awake nor aware

has some eye motions

Question 2

What are the characteristic of an individual in a persistant vegetative state

Answer 2

physiologically identifiable sleep/wake cycles appear

no evidence of awareness

Question 3

What are the characteristics of an individual who is minimally conscious

Answer 3

Eye/head motions
sleep/wake cycle
inconsistant awareness
inconsistent verbal responses

Question 4

What are the characteristics of an individual who is aware and alert

Answer 4

eye/head motions
sleep/wake cycle
awareness
verbal responses

Question 5

What is the hierchy of consciousness

Answer 5

coma to
Arousal/wakefulness to
awarness to
alertness

Question 6

where does injuries happen in the brain that disrupts consciousness?

Answer 6

much smaller lesions in the brainstem, midbrain or hypothalamus

Question 7

what is significant about the threshold for cortical neurons under a vegetative state?

Answer 7

the cortical neurons are up to 30mV velow threshold than under a normal conditions: this makes it very hard to depolarize the cell

(the cell is very hyperpolarized)

Question 8

What does the hierchy of consciousness suggest about the physiological basis of consciousness?

Answer 8

Different levels of consciousness/awareness are the result of different levels of cortical excitment

Question 9

What does the cortex need to become activated

Answer 9

both arousal and awareness require multiple sub cortical structures function to activate the cortex

Question 10

where does the production of EAA occur

Answer 10

Reticular Activating system

Parabrachial nuclei

Question 11

Where does the production of Cholinergic neurotransmitters occur

Answer 11

Pedunculopontine tegmental and laterodorsal nuclei

Question 12

Where does the production of noradrenergic occur

Answer 12

Locus ceruleus

Question 13

Where does the production of Serotonergic occur

Answer 13

Raphe nuclei

Question 14

Where does the production of the dopaminergic arousal system occur

Answer 14

ventral tegmental area

Question 15

Function, location, component and pathway of Reticular activating system

Answer 15

Occupies the mid-ventral portion of medulla and midbrain

loose collection of neurons and fiber tracts

receives all ascending sensory tracts, vision, and auditory, however the modal specificity of input converging here is lost, there fore the information all synapses on the same neuron, so the brain knows something happened but not what happened

Dorsal pathway and ventral pathway

Uses EAA/Glutamate

but has some interneurons releasing GABA and Aceytylcholine

Question 16

What is the dorsal pathway

Answer 16

info via non specific nuclei of the thalamus including the intralaminar nucleus of the thalamus

and then the info will move from there to higher levels of cortex

Arousal systems synapse on thalamus and then thalamocortical neurons travel to the cortical neurons

Question 17

What is the ventral pathway

Answer 17

Bypasses the thalamus

via the basal forebrain and hypothalamus

from there the info will diffuse to all higher levels of cortex

Travel straight from the arousal systems and synapse directly on cortical neurons

Question 18

Function, location, component and pathway of parabrachial nuclei

Answer 18

located in the pons (there is a medial, intermediate, and lateral nucleus)

crucial for arousal activation
similar sensory to RAS: receives all ascending sensory tracts, vision, and auditory

Output is just the ventral pathway with very extensive, very diffuse innervation of the entire cortex

uses EAA/Glutamate

Question 19

Function, location, component and pathway of Pedunculopontine tegmental and laterodorsal nuclei

Answer 19

Receive much input from all over that loses its modality specific information

output via the dorsal and ventral pathways

Pons

Acetylcholine

damage here can cause generalized slowing of cortical processes

Question 20

What arousal transmitters are important for achieving Arousal and wakefulness

Answer 20

EAA and Aceytlcholine (hyperpolarization and memory)

Question 21

Function, location, component and pathway of locus Ceruleus

Answer 21

Found in the pons

inputs: Paragignatocellularis nerve - sensory
Periaqueductal grey
higher centers including the cortex

Outputs: info releated to consciousness ascend to the cortex via both the dorsal and ventral pathways

also unrelated output to the spinal cord

help with startle and alerting responses
sleep wake
behavioral vigilance

Norepinephrine

Question 22

Function, location, component and pathway of Raphe nuclei

Answer 22

Inputs: Sensory from spinal cord (fine proprioception) trigeminal n

found in pons

Output: dorsal and ventral pathways
quiet awareness (arousal)
mood andaffect
modulation of pain

serotonin: 5HT

Question 23

What do we need to move from Arousal/wakefulness to Awareness

Answer 23

Norepinephrine and serotonin (startle/awareness)

Question 24

Function, location, component and pathway of Ventral tegmental area

Answer 24

Midbrain

Dopaminergic that is important for cognitive functions, motor activity and emotion

Question 25

What gets us from awareness to alertness

Answer 25

Dopamine (focus, attention)

Question 26

what do the non specific thalamocortical neurons release as neurotransmitters

Answer 26

EAA

also they will synapse on intracortical neurons that will release GABA on other cortical neurons

Question 27

What leads to the waves on the EEG

Answer 27

the alternating waves of excitation from EAA and GABA

Question 28

What is the RAS/Parabrachial EAA system crucial for

Answer 28

increasing general excitabillity of cortical neurons

Question 29

What does the cholinergic system add and what happens in alzheimer paitients with the cholinergic system

Answer 29

adds to that general excitation

in alzheimers the cholinergic systems are hit

mental processes slow dramatically and memory formation is profoundly impaired in the absence of excitation

Question 30

What does the noradrenergic and serotonergic systems do and how do these relate to an EEG

Answer 30

move us from being awake to being more generally aware of the incoming info

the alerting response in the EEG is an early indicator that the cortex is looking for sensory input

Question 31

What does the dopaminergic system add and what is the significance of Levodopa

Answer 31

adds focused awareness associated with novel stimuli

individuals in the persistent vegetative state can get treated with levodopa and produce dramatic increases in cognitive function

Question 32

During sleep what happens to thalamocortical neurons

Answer 32

they are hyperpolarized but will show slow occasional short bursts of action potentials

this hyperpolarization cuts the cortex off from the excitatory influence during the deepest levels of sleep