Lecture 6: Brain Arousal Systems

Question 1

Eye/head motions

Sleep/wake cycle

Awareness

Verbal responses

Which are active in Coma patients

Answer 1

None but eye/head motions due to spinal or cortical reflexes may be seen

Question 2

Eye/head motions

Sleep/wake cycle

Awareness

Verbal responses

Which are active in patient who is in a persistent vegetative state

Answer 2

Eye/ head motions

Sleep/wake cycles

Question 3

Eye/head motions

Sleep/wake cycle

Awareness

Verbal responses

Which are active in patient who has minimal consciousness

Answer 3

Eye/head motions

Sleep/wake cycle

Awareness - inconsistent or intermittent

Verbal responses - inconsistent or itermittent

Question 4

Eye/head motions

Sleep/wake cycle

Awareness

Verbal responses

Which are active in patient who is aware/alert

Answer 4

All of them

Question 5

What are the levels of cosciousness

Answer 5

1. Alertness
2. Awareness (minimal consciousness)
3. Arousal/Wakefulness (Persistent vegetative)
4. Coma

Question 6

What are the two parts of consciousness?

Answer 6

Arousal (being awake) Awareness (conscious processing of inputs)

Question 7

What parts of of consciousness is missing in a coma?

Answer 7

Arousal and Wakefulness (EEG shows nothing)

Awareness

Question 8

What parts of of consciousness is missing in a persistent vegetative state?

Answer 8

Awareness (Arousal is present on EEG)

Question 9

What has to be damaged in cerebral cortex to cause comatose state?

Answer 9

Bilateral and massive damage

Question 10

Injuries to what areas often cause disruptions to consciousness leading to a persistent vegative state?

Answer 10

Brainstem, Midbrain & Hypothalamus

Question 11

What is the status of cortical neurons in a persistent vegetative state?

Answer 11

Hyperpolarized (30 mv below threshold)

Question 12

State the Arousal System Heirachy

Answer 12

Question 13

What NTs take one from a coma to Arousal/Wakefulness?

Answer 13

EAA

Question 14

What supplies EAA

Answer 14

Reticular Activating System (RAS) - mid-ventral portion of medulla & midbrain

Parabrachial Nuclei - pons

Question 15

What supplies the Cholinergeric system

Answer 15

Pedunculopontine Tegmental (PPT) Laterodorsal Nuclei (LDT)

Question 16

Where supplies the Noradregenic (Norepinephrine) System

Answer 16

Locus Ceruleus

Question 17

Where are Dopaminergic inputs received from

Answer 17

Ventral Tegmental Area & Substantia Nigra

Question 18

What is the soruce of Seratonergic system?

Answer 18

Raphe Nucleus

Question 19

Why is Reticular Activating System not specific?

Answer 19

All sensory pathways converge at RAS and there is too much input - basically RAS is just an event detector

Question 20

How does RAS tell the cortex that something happened?

Answer 20

1. Dorsal pathway
2. Ventral pathway

Question 21

Where do the dorsal pathways go?

Answer 21

Arousal systems send axons to thalamus and synapse. Axons from thalamus then go to cortex to synapse.

Question 22

What are the axons from the thalamus to the cortex called in the dorsal pathway?

Answer 22

Thalamocortical neurons

Question 23

Ventral Pathway

Answer 23

Skips thalamus via basal forebrain and hypothalamus and send axons straight to cortex to synapse directly onto cortical neurons

Question 24

Difference between ventral and dorsal pathway

Answer 24

Ventral pathway

Release NTs produced by specific system

Dorsal pathway

1. first synapse in thalamus - releases the NTs produced by the specific pathway.
2. Second synapse in cortex - release NTs produced by specific system

Question 25

Differentiate between RAS & Parabrachial Nuclei

Answer 25

RAS located in midventral portion of medulla & midbrain / Parabrachial Nuclei located in pons RAS outputs utilizes dorsal & ventral pathways / Parabrachial Nuclei only uses ventral pathway Both are involved in general sensation Both release EAA

Question 26

Differentiate between RAS & PPT/LDT

Answer 26

1. Both RAS & PPT/LDT are involved general sensation and send their axons via the doral & ventral pathways. 2. RAS releases EAA (EAA system) 3. PPT/LDT releases Acethylcholine (Cholingeric system)

Question 27

What happens if there is damage to PPT/LDT?

Answer 27

Severe Cognitive Defects & Slowing of Cortical processes as seen in Alzheimer's

Question 28

What NTs take one from Arousal/Wakefulness (PVS) to Awareness (minimal consciousness)?

Answer 28

Norepinephrine & Serotonin

Question 29

What pathways are used to produce awareness

Answer 29

Both dorsal and ventral

Question 30

What does it mean for sensory inputs to the Locus Coereuleus to be processed? What does it release?

Answer 30

Sensory is no longer general as seen in RAS, PPT/LDT or parabrachial nuclei. Sensory receved in specific Norepinephrine

Question 31

What is the role of norepinephrine?

Answer 31

Startle and Alert (EEG Manifestation) Sleep - wake behavioral vigilance

Question 32

Where is serotonin released and what is the role of serotonin?

Answer 32

1. Raphe Nuclei 2. Quiet Awareness (general awareness) Mood & affect Modulation of pain

Question 33

What NT takes one from Awareness to Alertness and where is it produced?

Answer 33

Dopamine Ventral Tegmental Area (VTA)

Question 34

What does dopamine do?

Answer 34

Cognitive Function Motor Activity Emotion (pleasure)

Question 35

How are oscillations created on EEG?

Answer 35

Thalamocortical NTs release EAA (excitatory) and also bind to intracortical neurons to release GABA (inhibitory)

Question 36

What is affected in patients with Alzheimer's?

Answer 36

Cholinergic systems: slow mental processes and impaired memory formation

Question 37

What can treat some people in a persistent vegetative state

Answer 37

L - dopa (Levodopa)