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Flashcards in Mechanisms of Arousal Deck (44):
0

Consciousness is recognized by having two parts

1. arousal
2. awareness

1

arousal =

being awake

2

awareness=

conscious processing of inputs

3

Coma

neither awake (arousal absent) nor aware

4

Persistent vegetative state

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

5

minimally conscious state

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

6

Misconception with comatose state

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

7

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

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

8

What are the 5 types of arousal systems

EAA
cholinergic
noradrenergic
seratonergic
dopaminergic

9

What are the EAA activating regions

Reticular activating system (RAS)
parabrachial nuclei

10

What are the Cholinergic activating regions of the brain

pedunculopontine tegmental and laterodorsal nuclei
(PPT and LDT)

11

What is the Noradrenergic activating region of the brain

locus ceruleus

12

what is the seratonergic activating region

raphe nuclei

13

What is the dopaminergic activating region

ventral tegmental area

14

EAA: inputs to the RAAS

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

15

EAA: inputs to the RAS
describe how the RAS responds to multiple sensory modalities

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.

16

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

1. dorsal pathway
2. ventral pathway

17

Dorsal pathway

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

18

Ventral pathway

via basal forebrain and hypothalamus,
from there diffuse pathway to all higher levels.

19

EAA: RAS where is it found

occupies midventral portion of medulla and midbrain

20

EAA parabrachial nuclei - where are they located

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

21

EAA - parabrachial nuclei inputs

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

22

EAA parabrachial nuclei - outputs

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

23

EAA RAS and Para brachial nuclei - major NT used

EAA, glutamate - for both dorsal and ventral pathways

24

Things to be aware of with EAA arousal systems

within RAS, there is a substantial number of interneurons that release GABA

RAS also has a neuronal population that releases Ach

25

EAA - its role in arousal

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

AROUSAL

26

Cholinergic arousal system inputs

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

27

cholinergic arousal system output and major NT

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

28

Cholinergic - its role in arousal

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

29

Cholinergic - Role in arousal/awareness

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.

30

Noradrenergic - outputs from LC

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

31

Noradrenergic functions in arousal/awareness

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

32

Serotonergic inputs

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

33

Serotonergic outputs

for arousal both dorsal and ventral paths are used

34

Serotonergic functions

quite awareness

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

35

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

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

36

Thalamic arousal systems

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

37

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

EAA

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

EAA
general excitability of cortical neurons.
exceeds
hyperpolarized

39

The cholinergic system does what

adds to general excitation

40

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

cholinergic system

41

The noradrenergic and seroterneric systems do what

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

42

The dopaminergic system does what

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

43

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

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.