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Neuroendocrine Exam 2 > Brain arousal systems > Flashcards

Brain arousal systems Flashcards

1
Q

Consciousness has 2 parts. What are they?

A

arousal and awareness

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2
Q

are there any sleep/wake cycles in the comatose state?

A

no

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3
Q

what is characteristic of the persistent vegetative state?

A

sleep/wake cycles but no evidence of awareness

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4
Q

what is characteristic of the minimally conscious/ awareness state?

A

there are sleep/wake cycles, the patient has reproducible evidence of awareness (ability to respond to simple commands) but limited or absent communication

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5
Q

Most often, disruptions of consciousness result from what?

A

small lesions in the brainstem, midbrain, or hypothalamus

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6
Q

patients in a persistent vegetative state have cortical neurons that are what?

A

30 mv below threshold than under normal conditions (they are incredibly hyperpolarized)

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7
Q

different levels of consciousness/ awareness are the result of what?

A

different levels of cortical excitation

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8
Q

What is critical for arousing the cortex?

A

brainstem regions

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9
Q

What does the cortex require for activation since it does not have an intrinsic mechanism for activation?

A

it requires input from the midbrain/hindbrain regions

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10
Q

What system must be present for a patient to move from a comatose state to at least a persistent vegetative state?

A

the EAA system

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11
Q

What contributes to the EAA system (reticular activating system (RAS)) but if the EAA system it cannot move the patient from the comatose state to the PVS on its own?

A

the cholinergic system

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12
Q

Where is the RAS located?

A

mid ventral portion of the medulla and midbrain

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13
Q

where is the cholinergic system located?

A

in the pons

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14
Q

Where is the noradrenergic system located?

A

the locus ceruleus

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15
Q

where is the serotonergic system located?

A

raphe nuclei

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16
Q

where is the dopaminergic system located?

A

the ventral tegmental area

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17
Q

What inputs does the RAS receive?

A

all the ascending sensory tracts and also the cranial nerves: trigeminal, auditory, and visual

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18
Q

What is the result of the sufficient synaptic convergence of input to the neurons of the RAS?

A

modal specificity is lost “ I just know something happened not what happened”

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19
Q

There are two pathways from the EAAs system to the cortex. What are they?

A

dorsal pathway and ventral pathway

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20
Q

What happens in the dorsal pathway?

A

a neuron in the RAS sends an axon to the thalamus and then from there it heads to the cortex

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21
Q

what happens in the ventral pathway?

A

an axon goes straight from the RAS to the cortex

22
Q

there is a second group of EAA neurons arising. From where?

A

from the pons in the parabrachial nuclei

23
Q

What are the output pathways from the parabrachial nuclei?

A

it is exclusively ventral–> so it bypasses the thalamus and goes straight to the cortex

24
Q

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

A

EAA/Glutatmate

25
Q

within the RAS there is a substantial number of interneurons (neurons intrinsic to the RAS) that release what?

A

GABA

26
Q

There are 2 nuclei in the pons that are associated with the cholinergic excitation of the cortex. What are they?

A

the pedunculopontine tegmental and laterodorsal nuclei (PPT/ LDT)

27
Q

What are the output options for the cholinergic system?

A

dorsal (goes to the thalamus) or ventral (bypasses the thalamus)

28
Q

What is the major neurotransmitter used by the cholinergic system?

A

acetylcholine (ACh)

29
Q

What is the main purpose of the cholinergic system?

A

provides a baseline excitation that is crucial to cortical activity

30
Q

What would damage to the PPT or LDT nuclei result in?

A

it doesn’t necessarily cause coma, but it does produce severe cognitive deficits that are associated with a generalized slowing of cortical processes

31
Q

Where is the locus ceruleus located?

A

in the pons

32
Q

Once i have moved from the comatose state to the aroused/wakeful state, what is the first NT needed to get closer to being fully aware?

A

noradrenaline

33
Q

What is different about the input into the locus ceruleus compared to the RAS?

A

the input to the LC has undergone more neuronal processing

34
Q

What are the pathways used for the outputs from the LC related to consciousness?

A

they ascend to the cortex using both the dorsal and ventral pathways

35
Q

the locus ceruleus system has a very specific function. What is it?

A

it is responsible for producing the startle and alerting responses on the EEG (waking you up)

36
Q

Where are the serotenergic nuclei located?

A

raphe nuclei (in the pons)

37
Q

What is the input into the raphe nuclei?

A

sensory input from the spinal cord (fine proprioception) and the trigeminal nerve input

38
Q

What are the output pathways of the raphe nuclei in regards to arousal?

A

both the dorsal and ventral pathways are used

39
Q

What is the function of serotonin in the arousal pathway?

A

quiet awareness “i’m aware of everything around me”/ general awareness

40
Q

How do we get to the final step of being really alert?

A

we have to add yet another level of excitation in–> dopaminergic systems

41
Q

the ventral tegmental area provides a dopaminergic input that is important to many functions including what?

A

cognitive functions, motor activity, and emotion

42
Q

Axons from the thalamus to the cortex are known as what?

A

thalamocortical neurons

43
Q

in the dorsal pathway, it does not matter what NT is released in the thalamus, the neuron that leaves the thalamus and synapses in the cortex will release what?

A

EAAs

44
Q

in the ventral pathway, what is the NT that is released once it synapses directly onto the cortical neurons?

A

the one that is specific to that system

45
Q

The thalamocortical neurons synapse on the cortical neurons and what else?

A

the intracortical neurons

46
Q

what do the intracortical neurons release on other cortical neurons?

A

GABA

47
Q

What is believed to lead to the waves recorded on the EEG?

A

the alternating waves of excitation (due to EAA being released) and inhibition (due to the GABA being released)

48
Q

In Alzheimer’s disease, which systems are particularly hit hard?

A

the cholinergic systems

49
Q

the noradrenergic and serotenergic systems move us from what to what?

A

from being awake to being more generally aware of incoming information

50
Q

the alerting response on the EEG is an early indicator of what?

A

that the cortex is looking for sensory input

Neuroendocrine Exam 2 (17 decks)

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