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Med School Yr 2 > 7 - Basal Ganglia > Flashcards

7 - Basal Ganglia Flashcards

1
Q

hypokinetic movement disorder?

A

too little movementq

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2
Q

hyperkinetic movement disorder?

A

too much movement, and often abnormal involuntary movements

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3
Q

what is the input region of the basal ganglia?

A

striatum

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4
Q

what neurons are found within the striatum?

A

medium spiny neurones
interneurones

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5
Q

what type of neurones are medium spiny neurones?

A

GABAergic
neuropeptides

inhibitory

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6
Q

where do medium spiny neurones project to and from?

A

project from basal ganglia to other regions

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6
Q

where do interneurons project?

A

w/i the basal ganglia

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7
Q

what type of neurons are interneurons?

A

GABAergic
cholinergic

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8
Q

what are the two pathways that input into the striatum?

A
  • corticostriatal - main input
  • nigrostriatal - fine tunes excitation
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9
Q

what type of pathway is the corticostriatal pathway?

A

glutamatergic

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10
Q

where does the corticostriatal pathway receive input from?

A

whole cerebral cortex

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11
Q

what type of pathway is the nigrostriatal pathway?

A

dopaminergic

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12
Q

where does the nigrostriatal pathway receive input from?

A

substansia nigra pars compacta

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13
Q

when dopamine and glutamate interact, what do they do?

A

modulate synaptic strength

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14
Q

which dopamine pathway is direct?

A

D1

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15
Q

which dopamine pathway is indirect?

A

D2

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16
Q

what neuropeptide is associated with the D2 pathway?

A

enkephalin

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17
Q

what neuropeptide is associated with the D1 pathway?

A

dynorphin

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18
Q

what is the basal ganglia responsible for?

A

fine tuning the initiation, control and termination of movements

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19
Q

what are the different components of the basal ganglia?

6

A
  • putamen
  • caudate
  • globus pallidus internus
  • globus pallidus externus
  • substantia nigra
  • subthalmic nucleus
20
Q

the striatum refers specifically to what two components?

A

caudate and putamen

21
Q

what are hte two pathways involving dopamine in the basal ganglia?

A

indirect pathway
direct pathway

22
Q
A
23
Q

how does the indirect pathway affect movement>

A

negative modulator of movement

24
Q

how does the direct pathway affect movement?

A

positive modulator of movement

25
Q

how does dopamine affect the direct and indirect pathways within the basal ganglia?

A

increased movements by activating direct pathways and inhibiting indirect pathway

26
Q

outline how the direct pathway initiates movement?

A
  • motor cortex sends excitatory signals to the striatum via glutamate
  • striatum sends inhibitory signals to the GPi and SNr via GABA
  • stops their resting function which is to inhibit the thalamus
  • thalamus is now dis-inhibited
  • thalamus sends excitatory signals to motor cortex via glutamate
  • motor cortex allows movement to occur
27
Q

what role does dopamine play in the direct pathway w/i the basal ganglia?

A
  • activates stiatum by interacting with D1 receptors (excitatory)
  • increases striatum’s inhibitory effect
  • increases propensity towards movement
28
Q

outline how the indirect pathway regulatesmovement:

A
  • motor cortex sends excitatory signals to the striatum via glutamate
  • striatum sends inhibitory signals to the GPe via GABA
  • GPe sends reduced GABA signals to subthalmic nucleus
  • subthalmic nucleus is dis-inhibited = sends more glutamate to GPi
  • excites GPi = sends more inhibitory signals to the thalamus via GABA
  • thalamus is inhibited = sends less excitatory signals to motor cortex
  • no impules is sent down spinal cord = decreased movement
29
Q

what role does dopamine play in the indirect pathway w/i the basal ganglia?

A
  • binds to D2 receptors (inhibitory)
  • striatal neurons have reduced inhibition
  • supresses excitatory actions of subthalmic nucleus
  • GPi has less inhibition on the thalamus
  • increases motor cortec excitation
30
Q

what type of receptor are the D1 and D2 receptors?

A

G coupled protein receptors

31
Q

D1 and D2 are both G coupled receptors - what is their overall effect?

A
  • activates the conversion of ATP to cAMP
  • causes phosphorylation/activation of intracellular substrates
31
Q

what are levels of dopamine during resting conditions?

A

low synaptic and extrasynaptic levels

32
Q

what are dopamine levels in active movement?

A

phasic dopamine release

33
Q

which dopamine receptors are preferential in resting conditions?

A

D2

34
Q

which dopamine receptors are preferential in active movement/learning?

A

D1

35
Q

how are the dopamine pathways different in parkinsons?

A
  • relative overactivity of indirect pathways
  • relative underactivity of direct pathways
36
Q

what are 3 behavioural impairments in PD?

A
  • cognitive disturbances - later dementia related to Lewy body pathology
  • impulse behaviour
  • depression, anxiety
37
Q

impulse behaviours in PD are linked to what?

A

severe dopaminergic deficit in ventral striatal areas

38
Q

depression and anxiety in PD are linked to what?

A

monoamine cell loss in brainstem

39
Q

what are 4 hyperkinetic movement disorders?

A
  • chorea
  • dystonia
  • myoclonus
  • tic disorders
40
Q

what are three hallmarks of chorea?

A
  • rapid, random irregular movements
  • flitting between various muscle groups and body parts
  • motor impersistence - can’t maintain voluntary movements
41
Q

what is the pathophysiology of chorea?

A
  • relative overactivity of direct pathways - excessive movement
  • underactivity of indirect pathways - no suppression of unwanted movements
42
Q

what is the pathophysiology of Huntington’s disease?

A
  • selective loss of D2 receptor-bearing indirect pathway neurones = involuntary movements
  • later loss of direct pathway neurones = hypokinetic movement disorders
  • loss of encephalin in indirect pathways
43
Q

what DNA sequence is altered in Huntington’s disease?

A

expanded CAG repeats

44
Q

what are the two hallmarks of Tourette’s syndrome?

A
  • rapid, repetitive movements or vocalisations
  • comorbid neuropsychiatric illness - OCD or ADHD
45
Q

what is the pathophysiology of Tourette’s?

A
  • loss of cholinergic and GABAergic striatal interneuones = reduced basal ganglia inhibition
  • increased dopamine D2 receptor binding
46
Q
A

Med School Yr 2 (96 decks)

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