week 6 lectures (basil ganglia) Flashcards

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1
Q

where does the basil ganglia recieve its input from?

A

the cortex

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2
Q

what is the name of the loop that goes cortex-basil ganglia- thalamus- cortex?

A

the re-entrant loop

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3
Q

what are 4 sections of the basal ganglia? visualise where they are

A
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4
Q

visualise where the internal capsule is in a horizontal view

A
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5
Q

what is the striatum composed of?

A

the caudate nucleus

the putamen

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6
Q

what is the putamen + globus pallidus called?

A

the lentiform nucleus

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7
Q

where does information from the cortex land in the basal ganglia?

A

the striatum

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8
Q

where in the basal ganglia does information go to the thalamus from

A

the globus pallidus

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9
Q

is the basal ganglia output continuous or discreet?

A

there is a continuos inhibitory output that can either be increased or decreased

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10
Q

what are the two pathways running from the striatum to the globus pallidus

A

the indirect and the direct pathway

INDIRECT- striatum to globus pallidus internal segment to globus pallidus external segment

DIRECT - striatum to globus pallidus external segment

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11
Q

do the direct and indirect pathway do the same thing?

A
  • they work against each other
  • this is called balanced opposition
  • direct pathway inhibits
  • indirect pathway excites
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12
Q
A
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13
Q

how does the direct pathway make the thalamus more responsive

A
  • it inhibits the basal ganglia which is inhibitive
  • therefore it inhibits the inhabition leading to an excitatory change overall
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14
Q

how does the indirect pathway make the thalamus less responsive

A

striatum to Gpe cells inhibit the inhibitory output of GPe

this increases the activity in GPI

this means there is greater inhibtory output from the gpi

so the thalamus is less respnoive

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15
Q

does increased output from the basal ganglia lead to the thalamus being more or less responsive

A

more responsive, as basal ganglia output is inhibitory

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16
Q

where do dopaminergenic axons come from?

A

the substantia nigra (midbrain)

17
Q

what is the effect of increaased dopamine on the thalamus?

A
  • when dopamine levels increase the inhibition on the thalamus drops
18
Q

how does dopamine decrease the inhibition on the thalamus?

A
  • there are dopamine receptors on the direct (D1) and indirect (D2) neurons in the globus pallidus
  • D1 receptors are excitatory- so increases the direct pathways
  • D2 receptors are inhibitory- so decrease the indirect pathway
  • this makes the thalamus more responsive
19
Q

are the neurons of the striatum and globus pallidus spontaneously active

A

striatum no- only activated when stimulated by cortex

globus pallidus yes

20
Q

how is dopamine related to parkinsons

A
  • parkinsons disease is associated with a loss of dopamine
  • this means the thalamic activity is less
  • this meansthreshold for activity is raised
  • it is difficult to iniate movement
  • this loss of dopamine is due to the loss of the substantia nigra
21
Q

what is the cause of huntingtons disease?

A
  • a loss of striatal neurons in the indirect pathway
  • as a result the balance switches to favour the direct pathway
  • this means the thalamus is over responsive
  • this can result in exaggerated movements
22
Q

what are 4 other circuits influenced by the basal ganglia?

A

other motor circuits

dorsolateral prefrontal circuit

lateral orbitofrontal circuit

anterior cingulate circuit

23
Q

what does the dorsolateral prefrontal circuit do?

A

cognition and problem solving

24
Q

what does the lateral orbitofrontal circuit do?

A

empathy, social controls

25
Q

what does the anterior cingulate circuit do?

A

motivational responses

procedural learning