Arousal

Question 1

Coma?

Answer 1

Neither awake nor alert

Question 2

PVS?

Answer 2

Sleep/wake cycle present

No awareness

Question 3

Minimally conscious state?

Answer 3

Sleep/wake present
Some awareness (to simple commands)
Limited/absent communication

Question 4

What is the cause of most disruptions of consciousness?

Answer 4

Lesions of brainstem, midbrain and hypothalamus (not cortex)

Question 5

What role does brainstem play in arousal?

Answer 5

It needs to “wake up” the cortex, since the cortex has no intrinsic mechanism for activation

Question 6

List of arousal systems (in order of specificity)

Answer 6

EAA (RAS and PBN)
Cholinergic
Noradrenergic
Serotonergic 
Dopaminergic

Question 7

RAS

Answer 7

• @ midventral portion of medulla/midbrain
• all ascending sensory tracts send info to RAS
• descending tracts (trigeminal, auditory, visual) send info too

Question 8

Loss of modal specificity?

Answer 8

RAS knows something is happening, but can’t determine where input is coming from

Question 9

Dorsal pathway of RAS

Answer 9

• Goes through nonspecific thalamic nuclei (intralaminar nucleus of thalamus)
• Goes to higher brain centers from there

Question 10

Ventral pathway of RAS

Answer 10

• Bypasses thalamus, instead going through basal forebrain and hypothalamus
• Goes to high brain centers after

Question 11

Parabrachial Nuclei

Answer 11

• Pons
• Crucial for arousal/activation
• Similar sensory inputs as RAS

Question 12

What pathway do PBN exclusively use?

Answer 12

Ventral

Question 13

What NTs do RAS and PBN use?

Answer 13

EAA (glutamate)

RAS also releases Ach and GABA (via interneurons)

Question 14

Overall purpose of EAA system in arousal?

Answer 14

Provides a baseline level of excitement crucial to cortical activity

Question 15

Location of cholinergic system?

Answer 15

Pedunculopontine tegemental (PPT) and laterodorsal nuclei (LDT)

Question 16

Output pathways of PPT/LDT?

Answer 16

Dorsal and Ventral

Question 17

What level of specificity do PPT and LDT nuclei transmit?

Answer 17

Very basic (the modality-specific info is lost)

Question 18

Purpose of cholinergic system?

Answer 18

Baseline excitation (and arousal/awareness)
- Damage to PPT and LDT -- severe cognitive deficits (slowing of cortical processes) {Alzheimer's}

Question 19

Location of Noradrenergic system?

Answer 19

Locus Ceruleuns

Question 20

Inputs to Noradrenergic system?

Answer 20

• Paragigantocellularis (rostral medulla) for sensory info
• Periaqueductal grey
• Higher centers (cortex)

Question 21

Outputs of noradrenergic system?

Answer 21

• Ascending (dorsal and ventral)

- Descending (dorsal adrenergic bundle)

Question 22

Functions of noradrenergic system?

Answer 22

• Startling and alerting

- Behavior vigilance

Question 23

Serotonergic nuclei location?

Answer 23

Midline raphe nuclei

Question 24

Inputs to serotonergic system?

Answer 24

From spinal cord (proprioception, trigeminal, PAG)

Question 25

Output of serotonergic system?

Answer 25

Dorsal and Ventral

Question 26

Serotonergic system functions?

Answer 26

- Quiet awareness - Mood/affect - Modulation of pain

Question 27

Dopaminergic system location?

Answer 27

Ventral tegmental area (and substantia nigra)

Question 28

Function of dopaminergic system?

Answer 28

- Cognitive functions - Motor activity - Emotion

Question 29

Outputs of dopaminergic system?

Answer 29

Dorsal and Ventral

Question 30

Alzheimer's disease

Answer 30

- Cholinergic system is hit hard | - Mental processes slowed and memory formation impaired

Question 31

PVS and EAA?

Answer 31

- Rostral regions of brainstem show neuronal loss > that of cortex - Cortical neurons are 10-30 mV hyperpolarized vs. threshold

Question 32

What is the purpose of the alerting response from NE?

Answer 32

Early indicator that the cortex is expecting a sensory input

Question 33

What is happening with thalamocortical neurons during sleep?

Answer 33

They are hyperpolarized and have occasional bursts of activity - Cortex is cut off from excitatory influence during sleep