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BB2 > Basal Ganglia > Flashcards

Basal Ganglia Flashcards

1
Q

What are basal ganglia?

A

Neural structures deep within cerebral hemispheres

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2
Q

What is the function of basal ganglia?

A

Regulate movement

Process info. relating to emotion, motivation and cognition

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3
Q

How do basal ganglia regulate movement?

A
  • regulate intensity of slow/stereotypes movements
  • inhibit antagonistic unnecessary movements
  • switch motor programs to stop or start movements
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4
Q

What are the neural structures within the basal ganglia?

A
  • caudate nucleus
  • putamen
  • globus pallidus
  • substantia nigra (motor)
  • subthalamic nucleus (motor)
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5
Q

What are the features of the caudate nucelus?

A

C shaped
in frontal lobe
head, body, tail
tail tapers ending in temporal lobe

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6
Q

What are the features of the putamen?

A

Large rounded
Forebrain
Connected to caudate at caudate head region

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7
Q

What are the features of the globus pallidus?

A 
Internal segment (GPi) sends output to thalamus
External segment (GPe) relays info between basal ganglia nuclei and globus pallidus
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8
Q

What are the features of internal capsule?

A

White matter structure

Separates lentiform nucleus and caudate nucleus

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9
Q

What is the blood supply to the caudate nucleus?

A

Middle cerebral artery

Anterior cerebral artery

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10
Q

What is the blood supply to the putamen?

A

Middle cerebral artery

Anterior cerebral artery

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11
Q

What is the blood supply to the globus pallidus?

A

Middle cerebral artery

Anterior choroidal

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12
Q

What is the blood supply to the internal capsule?

A

Middle cerebral artery
Anterior cerebral artery
Anterior choroidal

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13
Q

What is the input into the basal ganglia?

A 
Cerebral cortex (frontal and parietal)
Substantia nigra
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14
Q

How does the cerebral cortex project to the basal ganglia?

A

Project directly to caudate nucleus and putamen
From association areas in frontal and parietal cortex
Projections are corticostriatal pathway

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15
Q

How does the substantia nigra project to the basal ganglia?

A

In midbrain
Dopaminergic input to caudate nucleus and putamen
Nigrostriatal pathway

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16
Q

Where do the substantia nigra and cerebral cortex input into?

A

Input zone of basal ganglia

caudate nucleus and putamen = corpus striatum

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17
Q

What are the main neurons in the corpus striatum?

A

Medium spiny neurons

75%

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18
Q

What does corpus striatum convergence produce?

A 
dendritic trees of medium spiny neurons 
inputs converge = 
- cortical neurons (glutamatergic)
- substantia nigra neurons (dopaminergic)
- local circuit neurons (GABAergic)

these all converge on globus pallidus and substantia nigra reticulata

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19
Q

What is the order of the corpus striatum convergence?

A

Cortex -> corpus striatum -> globus pallidus external -> globus pallidus internal or substantia nigra reticulata

20
Q

What is the output of the basal ganglia?

A
  • subthalamic nucleus
  • VA/VL thalamic nuclear complex
  • superior colliculus (controls eye movement)
21
Q

What are the features of the subthalamic nucleus?

A

small paired nuclei
below thalamus
input from cerebral cortex and external globus pallidus
projects to internal globus pallidus and substantia nigra reticulata

22
Q

What are the features of the VA/VL thalamus complex?

A

Input from internal globus pallidus
Projects directly to motor cerebral cortex areas
Loop within cerebral cortex

23
Q

What is the input into the corpus striatum?

A

Cortical

Via excitatory glutamate neurons

24
Q

Where are there inhibitory neurons?

A

Corpus striatum and globus pallidus

GABAergic inhibitory neurons

25
Q

What is disinhibition?

A

Inhibition of inhibition
Produces excitation
Double inhibition
2 inhibitory neurons in sequence

26
Q

What is an example of a direct pathway?

A

Excitatory Glutamatergic axons -> caudate and putamen -> internal globus pallidus -> motor thalamus and back to motor cortex

27
Q

What is an example of an indirect pathway?

A

Caudate and putamen inhibit globus pallidus external which inhibits subthalamic nucleus which excites globus pallidus internal which inhibits motor thalamus so that motor thalamus remains fixed and so supplementary motor cortex output remains fixed

28
Q

When is the direct and indirect pathway active/inactive?

A

At rest/undergoing repetitive movement => direct inactive and indirect is active
Tonic inhibitory input to motor thalamus prevents change in movement
When you want a change in movement direct pathway becomes active

29
Q

What receptors are expressed by the corpus striatum neurons?

A

D1 or D2

30
Q

What is the role of the D1 receptor?

A
  • increases cAMP
  • increases sensitivity of corpus striatum neurons to glutamate
  • projects to internal globus pallidus directly
31
Q

What is the role of dopamine on pathways?

A

Increases action of direct pathway via D1 receptors to activate motor program change
Decreases action of indirect pathway via D2 receptors to block motor program change

32
Q

What is the role of dopamine?

A

Allows motor programs to change and stop and start

33
Q

What are hypokinetic movement disorders?

A

e. g. Parkinson’s
- if balance of inhibitory signals in direct and indirect pathways are altered
- can also get hyperkinetic movement disorders which is not PD

34
Q

What are the characteristics of Parkinson’s?

A

Resting tremor
Slowness of movement (bradykinesia)
Muscular rigidity
Minimal facial expressions

35
Q

What is the cause of motor function defects in Parkinson’s?

A
  • loss of dopaminergic neurons in substantia nigra compacta which project to caudate and putamen
36
Q

What are the 3 stages of Parkinson’s?

A
  • early: cardinal symptoms, no medication related complications
  • PD with motor and non-motor complications, medication side effects, unrelieved symptoms
  • advanced life limiting with significant disability
37
Q

How to manage early PD?

A

Levodopa
Dopamine agonists
MAO-B inhibitor

38
Q

How to manage 2nd stage PD?

A

COMT inhibitor
Apomorphine
Amantadine

39
Q

How to manage 3rd stage PD?

A

Deep brain stimulation

40
Q

What is an example of a hyperkinetic movement disorder?

A

Huntington’s

41
Q

How is Huntington’s inherited?

A
  • autosomal dominant
42
Q

What are the characteristics of Huntingtons?

A

Mood alterations
Personality alterations
Defects in memory and attention
Involuntary movements

43
Q

What causes Huntington’s?

A

Defects in motor function due to loss of GABAergic neurons in corpus striatum which project to globus pallidus

44
Q

What is chorea?

A

Rapid involuntary jerk type movements, non-purposeful, dance like, distal
Greek to dance

45
Q

What is athetosis?

A

Slow involuntary smooth writing type movements, non-purposeful, writhing, distal
Greek to throw

46
Q

What is ballismus?

A

Rapid involuntary wild flinging type movements, non-purposeful, wild flinging, proximal
greek for not fixed

BB2 (31 decks)

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