7. Brain Arousal Systems

Question 1

Consciousness is recognized as having two parts, what are they and what do they mean?

Answer 1

arousal (being awake)

awareness (conscious processing of inputs)

Question 2

Coma means one is neither awake nor aware (conscious) which a persistent vegetative state means?

Answer 2

physiologically identifiable sleep/wake cycles appear

no evidence of awareness

Question 3

What is classified as having sleep/wake cycles, ability to respond to simple commands, and limited/absent communication?

Answer 3

minimally conscious state

Question 4

What is the tree from least to most conscious? 4

Answer 4

coma to arousal/wakefulness to awareness to alertness

Question 5

What kind of damage must occur in order for someone to be in a comatose state due to a cortical issue?

Answer 5

massive and bilateral cerebral cortex damage

Question 6

More often, disruptions of consciousness result from smaller lesions in which locations? as compared to the cortex

Answer 6

Brainstem
midbrain
hypothalamus

Question 7

Arousal and awareness require activation of the cortex but the cortex has no intrinsic mechanism for activation. so what provides the activation?

Answer 7

sub-cortical structures

Question 8

Which of the following can be seen with a Coma?
Eye/head movement
Sleep/wake cycle
awareness
verbal response

Answer 8

Eye/head movement: Sometimes
Sleep/wake cycle: no
awareness: no
verbal response: no

Question 9

What can be seen with Persistent vegetative state?
Eye/head movement:
Sleep/wake cycle:
awareness:
verbal response:

Answer 9

Eye/head movement: yes
Sleep/wake cycle: yes
awareness: no
verbal response: no

Question 10

What can be seen with minimally conscious state?
Eye/head movement:
Sleep/wake cycle:
awareness:
verbal response:

Answer 10

Eye/head movement: yes
Sleep/wake cycle: yes
awareness: maybe
verbal response: maybe

Question 11

What can be seen with aware/alert state?
Eye/head movement:
Sleep/wake cycle:
awareness:
verbal response:

Answer 11

Eye/head movement: yes
Sleep/wake cycle: yes
awareness: yes
verbal response: yes

Question 12

EAA arousal system has a reticular activating system (RAS), which are loose connections ofneurons and fiber tracts which occupy what region of the brain?

Answer 12

midventral portion of medulla and midbrain

Question 13

The RAS takes input from all ascending sensory tracts as well as what three?

Answer 13

trigeminal
auditory
visual

Question 14

There are so many synaptic convergence of input to the RAS that what is lost?

Answer 14

modal specificity is lost

Question 15

Modal specificity can be best described as?

Answer 15

the brain ONLY knows something happened, not exactly WHAT happened

Question 16

The output of information from the EAA RAS has two pathways, one is the dorsal pathway via the non-specific nuclei of the thalamus, including?

Answer 16

intralaminar nucleus of the thalamus, which diffuses to all high levels

Question 17

The second pathway for output of info from the RAS in the midventral portion of medulla and midbrain is the ventral pathway via?

Answer 17

basal forebrain and hypothalamus

Question 18

The parabrachial nuclei (medial lateral and intermediate) is located in the pons and are crucial for arousal /activation. What is the one BIG difference between parabrachial nuclei and RAS?

Answer 18

outputs are exclusively via ventral pathway through basal forebrain and hypothalamus

Question 19

What is the major NT utilized by both the parabrachial and RAS neurons?

Answer 19

EAA/Glutamate (dorsal and ventral pathways)

Question 20

EAA provides baseline excitation crucial to cortical activity (via dorsal and ventral pathways). The next arousal system is the cholinergic system which consists of which nuclei?

Answer 20

pedunculopontine tegmental and laterodorsal nuceli (PPT/LDT)

Question 21

Like RAS, PPT/LDT receives alot of info so modality is lost and outputs are via dorsal/ventral pathways but what is different?

Answer 21

NT is acetylcholine

Question 22

Damage to the PPN/LDT doesnt cause a coma but does produce what?

Answer 22

severe cognitive deficits which slow cortical processes (in pons)

Question 23

What will get you from coma to arousal/wakefulness?

Answer 23

EAA (RAS/parabrachial) and Cholinergic Systems

Question 24

To move from arousal/wakefulness to awareness you need more input via the noradrenergic system located?

Answer 24

locus ceruleus

Question 25

The noradrenergic system receives inputs from paragigantocellularis N (sensory info), periaqueductal grey (PAG) and what else?

Answer 25

higher centers / cortex

Question 26

Outputs from the locus ceruleus (noradrenergic) are both ascending and descending. Ascending paths go via?

Answer 26

become dorsal noradrenergic bundle and run with RAS in dorsal and ventral pathways

Question 27

What are the very important functions of the locus ceruleus noradrenergic system? (3)

Answer 27

startle and alerting (on EEG)
Sleep-wake
behavioral vigilance

(AWARENESS)

Question 28

The next arousal system is known as the serotonergic system located at the raphe nuclei. Receiving inputs from? (3)

Answer 28

sensory from SC, trigeminal, PAG

Question 29

What paths does the serotonergic system use for output for arousal?

Answer 29

VENTRAL and some dorsal pathways

Question 30

What are the main functions of the serotnergic system?

Answer 30

Quiet awareness

Question 31

What two things together gets you from arousal/wakefulness to awareness?

Answer 31

Noradrenergic and serotonergic systems

Question 32

The dopaminergic system is located at the ventral tegmental area and provides dopaminergic input that is important in? (3)

Answer 32

cognitive functions, motor activity, and emotion

Question 33

What system will get you from awareness to alertness?

Answer 33

Dopaminergic system

Question 34

Reminder: what is the dorsal pathway?

Answer 34

send axons to thalamus, synapse and axons sent to cortex

Question 35

Reminder: what is the ventral pathway?

Answer 35

axons to cortex, bypassing thalamus and synapse in cortical neurons

Question 36

From the thalamus, there is diffuse projection into the entire cortex using EAA at the NT. The neurons with EAA then do what?

Answer 36

interact with a series of intracortical neurons that release GABA to creat oscillations that are seen on the EEG

Question 37

The RAS and parabrachial EAA system are crucial for increasing general what?

Answer 37

excittability of cortical neurons (cholinergic adds to this)

Question 38

in a persistent vegetative state the rostral regions of pons/midbrain/thalamus shows neuronal loss that exceeds that of the cortex. Cortical neurons are 10-30 mV what?

Answer 38

hyperpolarized to their threshold

Question 39

Which system is hit hardest with a disease like alzheimers, which leads to slowe mental processing and impaired memory formation?

Answer 39

Cholinergic system

Question 40

The noradrenergic/serotonergic systems move us from awake to being aware of information. Alerting response in EEG is early indicator of?

Answer 40

cortex ‘looking’ / expecting sensory input

Question 41

The dopaminergic systems adds to the awareness. In a limited number of people in persisten vege state, treatment with what has produced a dramatic increase in cognitive function?

Answer 41

levaDOPA

Question 42

During sleep, the thalamocortical neurons are hyperpolarized and show occasional bursts. What does this hyperpolarization do?

Answer 42

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