Mechanisms of Arousal

Question 0

arousal =

Answer 0

being awake

Question 1

Consciousness is recognized by having two parts

Answer 1

1. arousal

2. awareness

Question 2

awareness=

Answer 2

conscious processing of inputs

Question 3

Coma

Answer 3

neither awake (arousal absent) nor aware

Question 4

Persistent vegetative state

Answer 4

physiologically identifiable sleep/wake cycles appear (arousal)
no evidence of awareness

Question 5

minimally conscious state

Answer 5

sleep wake cycles (arousal)
reproducible evidence of awareness - ability to respond to simple commands
limited or absent communication

Question 6

Misconception with comatose state

Answer 6

primarily from damage to cerebral corticies
(this can be true, but damage must be massive)

Led to the hypothesis that BRAINSTEM regions are critical for arousing the cortex

Question 7

Both arousal and awareness require the activation of the _____
what is the caveat to this
how do we resolve it

Answer 7

cortex
the cortex has no intrinsic mechanism for activation
there are multiple subcortical structures that function to provide the activation required for the cortex to function

Question 8

What are the 5 types of arousal systems

Answer 8

EAA
cholinergic
noradrenergic
seratonergic
dopaminergic

Question 9

What are the EAA activating regions

Answer 9

Reticular activating system (RAS)

parabrachial nuclei

Question 10

What are the Cholinergic activating regions of the brain

Answer 10

pedunculopontine tegmental and laterodorsal nuclei

PPT and LDT

Question 11

What is the Noradrenergic activating region of the brain

Answer 11

locus ceruleus

Question 12

what is the seratonergic activating region

Answer 12

raphe nuclei

Question 13

What is the dopaminergic activating region

Answer 13

ventral tegmental area

Question 14

EAA: inputs to the RAAS

Answer 14

all ascending sensory tracts send information to the RAS, as well as
trigeminal
auditory
visual

Question 15

EAA: inputs to the RAS

describe how the RAS responds to multiple sensory modalities

Answer 15

there is sufficient synaptic convergence of input to the neurons of the RAS that MODAL SPECIFICITY IS LOST.

the neurons of the RAS respond equally well to multiple sensory modalities.

Question 16

EAA: Outputs from the RAS - waht are the two pathways

Answer 16

1. dorsal pathway

2. ventral pathway

Question 17

Dorsal pathway

Answer 17

via non specific nuclei of the thalamus, including the intralaminar nucleus of the thalamus
from there, diffuse pathway to all higher levels

Question 18

Ventral pathway

Answer 18

via basal forebrain and hypothalamus,

from there diffuse pathway to all higher levels.

Question 19

EAA: RAS where is it found

Answer 19

occupies midventral portion of medulla and midbrain

Question 20

EAA parabrachial nuclei - where are they located

Answer 20

located in the pons, (medial, intermediate and lateral parabrachial nuclei)

Question 21

EAA - parabrachial nuclei inputs

Answer 21

sensory inputs are similar to those seen in RAS, all/most of the sensory inputs in the body

Question 22

EAA parabrachial nuclei - outputs

Answer 22

exclusively via the ventral pathway, with extensive very diffuse innervation of the entire cortex

Question 23

EAA RAS and Para brachial nuclei - major NT used

Answer 23

EAA, glutamate - for both dorsal and ventral pathways

Question 24

Things to be aware of with EAA arousal systems

Answer 24

within RAS, there is a substantial number of interneurons that release GABA RAS also has a neuronal population that releases Ach

Question 25

EAA - its role in arousal

Answer 25

regardless of path (dorsal or ventral) the EAA system appears to provide a baseline excitation that is crucial to cortical activity AROUSAL

Question 26

Cholinergic arousal system inputs

Answer 26

like the RAS, the PPT/LDT nuclei receive so much input that all modality specific information is lost

Question 27

cholinergic arousal system output and major NT

Answer 27

output - dorsal and ventral pathways used by the RAS | major NT - Acetylcholine

Question 28

Cholinergic - its role in arousal

Answer 28

regardless of path (dorsal of ventral) the cholinergic system appears to provide a baseline excitation that is crucial to cortical activity (arousal)

Question 29

Cholinergic - Role in arousal/awareness

Answer 29

activity in the cholinergic inputs from the pons is also associated with arousal and awareness damage specifically to the PPT and DLT doesn't necessarily cause coma, but does produce severe cognitive deficits that are associated with a generalized slowing of cortical processes.

Question 30

Noradrenergic - outputs from LC

Answer 30

both ascending and descending ascending= dorsal AND ventral with the RAS the ascending fibers from this group of cells become the dorsal noradrenergic bundle

Question 31

Noradrenergic functions in arousal/awareness

Answer 31

startle and alerting responses to the EEG sleep wake behavioral vigilance (takes us to awareness)

Question 32

Serotonergic inputs

Answer 32

multiple, difficult to decide which ones relate to arousal systems.

Question 33

Serotonergic outputs

Answer 33

for arousal both dorsal and ventral paths are used

Question 34

Serotonergic functions

Answer 34

quite awareness other non RAS activities include mood and affect, modulation of pain

Question 35

Dopaminergic - Ventral tegmental area provides a dopaminergic input that is important to many functions including

Answer 35

cognitive functions motor activity emotion (dopamine is our icing on the cake)

Question 36

Thalamic arousal systems

Answer 36

Dorsal pathways synapses in the non specific nuclei of the thalamus from thalamus, there is a diffuse projection to the entire cortex utilising eaa as the NT these neurons interact with a series of intracortical neurons that releas GABA, to create oscillations seen in the EEG

Question 37

Thalamic arousal systems | from the thalamus, the diffuse projections release what NT?

Answer 37

EAA

Question 38

The RAS/ parabrachial _____ system is crucial for increasing________. in a persistent vegitative state, the rostral regions of the pons/midbrain/thalamus show neuronal loss that ____ that of cortex. Cortical neurons are _______ relative to their threshold

Answer 38

EAA general excitability of cortical neurons. exceeds hyperpolarized

Question 39

The cholinergic system does what

Answer 39

adds to general excitation

Question 40

In alzheiers, metnal processes slow dramatically and memory formation is impaird profoundly. what system is damaged

Answer 40

cholinergic system

Question 41

The noradrenergic and seroterneric systems do what

Answer 41

move us from being awake to being more generally aware of incoming information. the alerting response in the EEG is an early indicator that the cortex is 'looking for' or 'expecting' sensory input

Question 42

The dopaminergic system does what

Answer 42

adds to awareness, but its role is not as well defined.

Question 43

Thalamic arousal systems the activity of the thalmocortical neurons does or does not change with state explain

Answer 43

does during sleep these neurons are hyperpolarized and show occasional bursts (spindle- like discharges) this hyperpolarization essentially cuts the cortez off from the excitatory influence during the deepest levels of sleep.