Brain Arousal Systems

Question 1

What is the difference between arousal and awareness?

Answer 1

Arousal = being awake
Awareness = conscious processing

Question 2

What is a persistent vegetative state?

Answer 2

Physiologically identifiable sleep/wake cycles with no evidence of awareness

Question 3

What is a minimally conscious state?

Answer 3

Sleep/wake cycles, some evidence of awareness, ability to respond to simple commands, may have limited communication (yes/no)

Question 4

What are the most common causes of disruptions to consciousness?

Answer 4

Lesions in the brainstem, midbrain, or hypothalamus (rather than bilateral injury to cerebrum)

Question 5

Where do the EAAs arise?

Answer 5

Reticular activating system (RAS) and parabrachial nuclei

Question 6

Where is the RAS located?

Answer 6

Mid-ventral portion of medulla and midbrain

Question 7

What is the RAS?

Answer 7

A loose collection of neurons and fiber tracts

Question 8

Where does the RAS receive sensory input information from?

Answer 8

All ascending sensory tracts as well as trigeminal, auditory, and visual (but no specificity)

Question 9

What happens after RAS receives input?

Answer 9

Dorsal pathway: neurons ascend to the thalamus and release EAAs activating neurons that go all over the brain
Ventral pathway: bypasses thalamus, instead synapses occur in hypothalamus and basal forebrain

Question 10

What is the parabrachial nuclei?

Answer 10

Located in pons, crucial for arousal/activation via EAAs. Receives all sensory inputs to the body

Question 11

What happens after parabrachial nuclei receives input?

Answer 11

Only uses ventral pathway

Question 12

What are the pedunculopontine tegmental and laterodorsal nuclei?

Answer 12

Also receive sensory input that is non-specific like RAS. Major NT is Ach rather than EAA

Question 13

What systems must be in place to move from coma to arousal/wakefulness?

Answer 13

EAA/Ach (parabrachial nuclei and PNT/LDT)

Question 14

What systems must be in place to move from arousal/wakefulness to awareness?

Answer 14

Locus ceruleus (norepi) and raphe nuclei (serotonin/5HT)

Question 15

What is the locus ceruleus?

Answer 15

Area in same level of pons as parabrachial nuclei, processes sensory information in more specific way though. Uses both dorsal and ventral pathway to send information to the cortex. Important in startle/alerting responses (norepinephrine)

Question 16

What is the raphe nuclei?

Answer 16

Receives sensory input from spinal cord, uses both dorsal and ventral pathway to pass information along to cortex. Important in “quiet awareness” via serotinin. (Recognition of things going on but not focused on them)

Question 17

What systems must be in place to move from awareness to alertness?

Answer 17

Dopaminergic (ventral tegmental area)

Question 18

What is the ventral tegmental area (VTA)?

Answer 18

Provides dopaminergic input important in cognitive functions, motor activity, emotion

Question 19

What are the neurons in the dorsal pathway called?

Answer 19

Thalamocortical neurons (go from thalamus to cortex) and intercortical neurons (stay in cortex)

Question 20

What pathway is disrupted in Alzheimer’s patients?

Answer 20

Ventral pathway

Question 21

What do thalamocortical neurons and intercortical neurons release?

Answer 21

Thalamocortical neurons release EAA, intercortical neurons release GABA