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Neuroscience > Brain Arousal Systems > Flashcards

Brain Arousal Systems Flashcards

1
Q

Being awake

A

Arousal

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2
Q

Conscious processing of inputs

A

Awareness

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3
Q

Neither awake or aware

A

Coma

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4
Q
  • physiologically identifiable sleep/wake cycles appear

* no evidence of awareness

A

Persistent vegetative state

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5
Q
  • sleep/wake cycles
  • reproducible evidence of awareness – ability to respond to simple commands.
  • limited or absent communication
A

Minimally conscious state

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6
Q

Order of consciousness

A

Coma –> Arousal/Wakefulness –> Awareness–> Alertness

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7
Q

It is a common misperception that the comatose state results from damage to the cerebral cortices. But really?

A

More often, disruptions of consciousness result from much smaller lesions in the brainstem, midbrain, or hypothalamus

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8
Q

What does this “hierarchy“ of consciousness suggest about the physiologic basis of consciousness?
(first stage)

A
  1. Different levels of consciousness/awareness are the result of different levels of cortical excitation.
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9
Q

Arousal Systems
EAA:
- ?
- ?

A
  • Reticular Activating System (RAS)

* Parabrachial nuclei

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10
Q 
Arousal Systems 
• Cholinergic : ?
• Noradrenergic:  ?
• Serotonergic:  ?
• Dopaminergic: ?
A
  • Pedunculopontine tegmental and Laterodorsal
    nuclei (PPT/LDT)
  • Locus Ceruleus
  • Raphe nuclei
  • ventral tegmental area
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11
Q

Reticular Activating System Location

A

Occupies “mid-ventral portion” of medulla & midbrain

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12
Q

All ascending sensory tracts send information to the RAS

- Also send info to RAS: ?

A

As do:
• Trigeminal
• Auditory
• Visual

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13
Q

RAS:

All inputs synapse on the same post synaptic cell

A

convergence

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14
Q

There is sufficient synaptic convergence of input to the neurons of the RAS that ? is lost

A

modal specificity

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15
Q

2 pathways for RAS

  • ?
  • ?
A

Dorsal and Ventral Pathway

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16
Q

Dorsal Pathway
•Via the non-specific nuclei of the thalamus, including the ?

•From there, diffuse pathway to all higher levels

A

intralaminar nucleus of the thalamus

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17
Q

Ventral Pathway
•Via ? and ?

•From there, diffuse pathway to all higher levels

A

Via basal forebrain and hypothalamus

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18
Q

Goal of the Reticular System

A

To excite the cortex

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19
Q

Parabrachial Nuclei

- Location and Function?

A

Located in the pons, the parabrachial nuclei (medial, intermediate, and lateral) are crucial for arousal/activation.

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20
Q

What is the one big difference between the Parabrachial Nuclei and RAS?

A

The outputs for the Parabrachial Nuclei are likely exclusively via the Ventral pathway
- With extensive, very
diffuse innervation
of the entire cortex.

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21
Q

The major neurotransmitter utilized by both the

parabrachial and the RAS neurons is?

A

EAA/Glutamate
(That is true for both dorsal and
ventral pathways)

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22
Q

Regardless of path (dorsal or ventral), the ? system appears to provide a baseline excitation that is crucial to cortical activity.

A

EAA

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23
Q

Cholinergic: Pedunculopontine tegmental (PPT) and Laterodorsal nuclei (LDT)
- Like the RAS, the PPT/LDT nuclei receive so much input that all modality-specific information is lost.

  • Outputs are via the ? and ? pathways used by the RAS
A
  • Dorsal

- Ventral

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24
Q

Major neurotransmitter of PPT/LDT?

A

ACETYLCHOLINE!

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25
Q
  • The ? pathway skips the thalamus

- The ? pathway goes through the thalamus

A
  • Ventral

- Dorsal

26
Q

Regardless of path (dorsal or ventral), the ? system ALSO appears to provide a baseline excitation that is crucial to cortical activity.

A

Cholinergic

27
Q

Activity in the ? inputs from the pons is ALSO associated with arousal and awareness.

Damage specifically to the ? doesn’t necessarily cause coma, but does produce severe cognitive deficits that are associated with a generalized slowing of cortical processes.

A
  • cholinergic

- PPN/DLT

28
Q

So from coma –> arousal/wakefulness; what is above the arrow?

A

EAA/Ach

29
Q

What does this “hierarchy“ of consciousness suggest about the physiologic basis of consciousness?
(second stage)

A
  1. Moving from arousal/wakefulness

to awareness takes additional excitation.

30
Q

Noradrenergic: Locus Ceruleus

  • Releases?
  • Location ?
A
  • Releases NE

- Location is Brainstem area

31
Q

Inputs to the L.C.:

?

A 
• Paragigantocellularis n (in
rostral medulla) – sensory
information
•PAG – periaqueductal grey
•Higher centers, including
the cortex
32
Q

Note that this information has undergone more neural processing than the sensory inputs received by the EAA/Ach systems.
(which area are they talking about ?)

A

Locus Ceruleus

33
Q

Outputs from the L.C.:

?

A

•Both ascending & descending

•Ascending:
- dorsal & ventral with the RAS

34
Q

L.C. :

The ascending fibers from this group of cells become the ?

A

dorsal noradrenergic bundle

35
Q

Functions of the L.C. NA system: ?

A

•Startle & alerting
responses on the EEG **
•Sleep-wake
•behavioral vigilance

36
Q

Inputs of Raphe nuclei?

A

• Sensory – from spinal
cord (fine proprioception),
trigeminal, PAG

37
Q

Outputs of Raphe nuclei?

A

For Arousal, both the dorsal and ventral paths are used (there other outputs that relate to other functions of the raphe)

38
Q

Functions of Raphe nuclei?

A

•Quiet awareness
•Other (non-RAS activities) include:
- Mood and Affect
- Modulation of Pain

39
Q

Arousal/Wakefulness –> Awareness; what is above the arrow?

A

NE/5HT

40
Q

What does this “hierarchy“ of consciousness suggest about the physiologic basis of consciousness?
(third stage)

A
  1. Moving to full awareness takes another layer of excitation to achieve.
41
Q

Dopaminergic: ventral tegmental area (VTA)

  • strongly associated with?
A

Mood and affect

42
Q

The VTA (along with the Substantia Nigra) provides a dopaminergic input that is important to many functions, including: ?

A
  • Cognitive functions
  • Motor activity
  • Emotion
43
Q

? input is important for moving us into awareness

A

Dopaminergic

44
Q

Awareness –> Alertness; what is above the arrow?

A

DA

45
Q

Which Pathway?
• Arousal systems
send axons to
thalamus

• Synapse

• Axons from
thalamus to
cortex

A

Dorsal Pathway

goes through thalamus!!

46
Q

Which pathway?
• Arousal systems
send axons straight to
cortex

• Synapse directly onto
cortical neurons

A

Ventral Pathway

bypasses thalamus!!

47
Q

Thalamic Arousal System

• Dorsal pathway synapses in the ?

A
  • non-specific nuclei of the thalamus (e.g. intralaminar)

(Non-specific is a misnomer – it is in contrast to the sensory-specific nuclei of the thalamus and reflects an old belief that these thalamic nuclei did not have specific projections/functions)

48
Q

Thalamic Arousal System:

  • From the thalamus, there is a diffuse projection to the entire cortex, utilizing ? as the neurotransmitter.
A

EAA

49
Q

Thalamic Arousal System:

  • These neurons (with their EAA input) interact with a series of ? neurons that release ?, to create oscillations that are seen in the EEG.
A
  • intracortical

- GABA

50
Q

The Function of all Arousal Systems #1

A
  1. The RAS/Parabrachial EAA system is crucial for increasing general excitability of cortical neurons
51
Q

The Function of all Arousal Systems

  • In a persistent
    vegetative state, the rostral regions of the pons/midbrain/thalamus show neuronal loss that exceeds that of the cortex.
  • Cortical neurons are 10 – 30 millivolts ? relative to their threshold.
A

HYPERPOLARIZED

52
Q

The Function of all Arousal Systems #2

A
  1. The cholinergic system adds to that general excitation.
53
Q 
In ? disease, the
cholinergic systems
are particularly
hard hit.  Mental
processes slow
dramatically and memory formation is profoundly
impaired.
A

Alzheimer’s

54
Q

The Function of all Arousal Systems #3

A
  1. The noradrenergic and serotonergic systems move us from being awake to being more generally aware of incoming information.
55
Q

The ? response in the EEG is an early indicator
that the cortex is ‘expecting’ sensory
‘looking’ for or
input.

A

alerting

56
Q

The Function of all Arousal Systems #4

A
  1. The dopaminergic system adds to that awareness, particularly focused awareness associated with novel stimuli, but its role is not as well defined.
57
Q

In a limited number
of people in a
persistent vegetative state, treatment with ? has produced
dramatic increases in cognitive function.

A

levodopa

58
Q

Thalamic Arousal Systems
- During sleep, the ? are hyperpolarized and show occasional bursts (spindle-like discharges).

  • This hyperpolarization essentially cuts the cortex off from the excitatory influence during the deepest levels of sleep.
A
  • thalamocortical neurons
59
Q

Coma –> Arousal/Wakefulness

  • What is component and function is above the arrow?
A
  • EAA/Ach

- Hyperpolarization/memory

60
Q

Arousal/Wakefulness –> Awareness

  • What is component and function is above the arrow?
A
  • NE/5HT

- Startle/awareness

61
Q

Awareness –> Alertness

  • What is component and function is above the arrow?
A
  • DA

- Agonists improve cognitive function

Neuroscience (14 decks)

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