Phys - Brain Arousal Systems

Question 1

describe coma

Answer 1

neither awake or aware

• no sleep/wake cycles
• EEG waves normally abnormal

Question 2

describe persistent vegetative state

Answer 2

physiologically identifiable sleep/wake cycles
- no evidence of awareness
- EEG may or may not be abnormal
(the “arousal/wakefulness” level of consciousness)

Question 3

describe minimally conscious state

Answer 3

pt has sleep/wake cycles

• reproducible evidence of awareness; ability to respond to simple commands
• limited or absent communication

Question 4

are disruptions of consciousness usually from damage to cerebral cortex?

Answer 4

it can be, but the damage would have to be massive and bilateral
- more often from smaller lesions in brainstem, midbrain, or hypothalamus

Question 5

what is the reticular activation system (RAS)?

- what tracts use it?

Answer 5

a type of arousal system that uses EAA

- all ascending sensory tracts send info to the RAS

Question 6

where is the RAS located

Answer 6

mid-ventral portion of medulla and midbrain

Question 7

why does the RAS system lose modal specificity?

Answer 7

there is sufficient synaptic convergence of input to the neurons of RAS that it loses specificity

Question 8

compare the two pathways of the RAS

Answer 8

dorsal: synapses in intralaminar nucleus of thalamus
ventral: goes through basal forebrain and hypothalamus but NOT the thalamus

Question 9

where are the parabrachial nuclei located

Answer 9

in the pons

Question 10

what inputs go to the parabrachial nuclei?

Answer 10

similar to RAS; all/most of the sensory inputs in the body

Question 11

what pathway do the parabrachial nuclei use

Answer 11

ventral pathway (bypass the thalamus)

Question 12

where in the cortex do the parabrachial nuclei innervate?

Answer 12

diffuse innervation of the entire cortex

Question 13

what is the major NT utilized by both parabrachial nuclei and RAS

Answer 13

EAA/glutamate

Question 14

what other NTs does the RAS release?

Answer 14

GABA

Ach

Question 15

why do the PPT/LDT nuclei lose modal specificity?

Answer 15

they receive so much input that specificity is lost

Question 16

major NT of the PPT/LDT?

Answer 16

Ach

Question 17

outputs from the PPT/LDT use what pathway?

Answer 17

the dorsal (through thalamus) and ventral (bypasses thalamus) pathways

Question 18

damage to the PPT/LDT causes what?

Answer 18

produces severe cognitive deficits that are associated with a generalized slowing of cortical processes
- not coma though

Question 19

transmission of EAA and Ach will get you to what level of the consciousness hierarchy?

Answer 19

from coma –> arousal/wakefulness (persistent vegetative state)

Question 20

what type of system is the locus ceruleus

Answer 20

noradrenergic (produces NE)

Question 21

input from the paragigantocellular nerve in the rostral medulla goes to what brain arousal system, and what kind of info is it

Answer 21

locus ceruleus

- sensory input from all ascending tracts

Question 22

input from the PAG goes to what brain arousal system

Answer 22

locus ceruleus

Question 23

compare incoming information in the locus ceruleus to that in the EAA/Ach systems

Answer 23

info going to the locus ceruleus has undergone more neural processing than the sensory inputs received by EAA/Ach systems

Question 24

describe the pathway of output information from the locus ceruleus

Answer 24

joins axons from RAS/parabrachial/PPT/LDT in the dorsal and ventral pathways to become the dorsal noradrenergic bundle

Question 25

functions of the locus ceruleus noradrenergic system

Answer 25

startle and alerting responses on EEG - sleep/wake - behavioral vigilance

Question 26

what is the input information to the raphi nucleus

Answer 26

- sensory from spinal cord - trigeminal sensory nucleus - PAG (proprioception)

Question 27

what pathways does output information from raphi nucleus use

Answer 27

dorsal and ventral pathways | mostly ventral

Question 28

what is the function of the serotonergic (raphi nucleus) brain arousal system

Answer 28

quiet awareness - mood and affect - modulation of pain

Question 29

describe the pathway and NTs from coma to alertness

Answer 29

coma --(EAA/Ach)--> arousal/wakefulness --(NE/5HT)--> awareness --(dopaminergic)--> alertness

Question 30

what arousal system will get you from awareness to full alertness

Answer 30

dopaminergic (ventral tegmental area)

Question 31

where is the ventral tegmental area

Answer 31

midbrain

Question 32

function of dopaminergic input

Answer 32

cognitive function motor activity emotion

Question 33

what pathway does the dopaminergic pathway use

Answer 33

dorsal (goes through thalamus) and ventral (bypasses thalamus)

Question 34

what causes the oscillations on an EEG

Answer 34

from the thalamus there is a diffuse projection to the entire cortex using EAA as an NT --> EAA interacts with intracortical neurons that release GABA --> creates oscillations on EEG

Question 35

in a persistent vegetative state, what state are the cortical neurons in

Answer 35

10-30 mV hyperpolarized relative to their threshold

Question 36

what brain arousal systems are hit in Alzheimer's

Answer 36

cholinergic (PPT/LDT)

Question 37

what systems move us from being awake to more generally aware of incoming information

Answer 37

noradrenergic (locus ceruleus) and serotonergic (raphi nucleus)

Question 38

describe the thalamocortical neurons during sleep and the significance of this

Answer 38

the thalamocortical neurons are hyperpolarized and show occasional bursts (spindle-like discharges) --> this cuts the cortex off from excitatory influence during sleep