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Block 3 > Basal Ganglia > Flashcards

Basal Ganglia Flashcards

1
Q

Describe the general circuit of basal ganglia activity.

A

Primary motor cortex activity excites the basal ganglia

BUT Basal ganglia activity (can be upregulated/downregulated) INHIBITS the thalamus which would then inhibit supplementary/pre-motor cortexes + the primary motor cortex reducing muscle activity via CST/CBT

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2
Q

What are the functions of the supplementary and pre-motor cortexes?

A

Aid in planning motor activity

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3
Q

What symptoms would thalamic damage cause? Why?

A

Deficits in motor initiation, control and learning as usually activity of it would excite the supplementary/pre-motor cortexes which would excite the primary motor cortex which would send output to muscles via CST/CBT

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4
Q

What are the main component parts of basal ganglia?

A 
Caudate nucleus
Putamen
Globus pallidus internus (GPI) (medius) 
Globus pallidus externus (GPE) (lateralis)
Thalamus (part of)
Subthalamic nucleus (STN)
Substantia Nigra Pars Reticulata (SNPR)
Substantia Nigra Pars Compacta (SNPC)
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5
Q

Where does the basilar artery sit?

A

Medial and in front of the pons

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6
Q

Where do basal ganglia nuclei sit?

A

Deep in the cerebral hemispheres and midbrain

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7
Q

What does the word pallidus mean?

A

‘Pale’ so in comparison to structure next to it which is the putamen nucleus

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8
Q

What does the word putamen mean?

A

Translates to prune so looks dark brown and wrinkly

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9
Q

How can deep brain nuclei of basal ganglia be identified on medical images?

A

Position

Different signal intensity (due to darkness/brightness of structure)

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10
Q

Where is the caudate nucleus?

A

The pair of nuclei are large in size connecting anteriorly with the putamen and following the curve of the lateral ventricle

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11
Q

What structures make up the lentiform nucleus?

A

Putamen + globus pallidus (internus + externus)

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12
Q

Where is the substance nigra (SN)?

A

Midbrain region - on L and R (paired nuclei)

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13
Q

What structures make up the striatum?

A

Caudate nucleus + putamen

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14
Q

What structure makes up the pallidum?

A

Globus pallidus internus (medius) + globus pallidus externus (lateralis) + SN pars reticula (SNPR)

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15
Q

What is the thalamus?

A

2 paired thalami (L + R hemisphere) representing an organized dense collection of deep brain nuclei of sensory, visual, auditory, limbic + motor-associated functions sitting medial to the 3rd ventricle with the IC sitting immediately lateral

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16
Q

What is the function of the ventral posterior nucleus of the thalamus?

A

Relay nucleus for multiple sensory modalities (touch, pain, temperature + taste) getting input from spinothalamic tract, medial lemniscus + trigeminothalamic tracts

Lateral: body
Medial: Face - CNV

17
Q

What is the function of the ventral lateral nucleus of the thalamus?

A

Connects cerebellum to primary motor cortex

18
Q

What is the function of the ventral anterior nucleus of the thalamus?

A

Connects basal ganglia to premotor cortex

19
Q

What is the function of the lateral geniculate body of the thalamus?

A

Relay for optic tract fibres

20
Q

What is the function of the medial geniculate body of the thalamus?

A

Relay for auditory pathway fibres

21
Q

What is the function of the pulvinar of the thalamus?

A

Connects lateral geniculate body to visual association regions

22
Q

What is the function of the medial nucleus of the thalamus?

A

Connects to frontal cortex (emotion, drive, motivation + instinctive drives)

23
Q

What is the function of the anterior nucleus of the thalamus?

A

Connects to mammillary bodies of limbic system (mood, emotion + memory)

24
Q

What does the basal ganglia and cerebellum to do the motor cortex?

A

Modulate its activity and ‘fine tune’ its output via the thalamus through the CST and to lower motor neuron cell bodies allowing us to have wanted movement and get rid of unwanted movement

25
Q

What is the current hypothesis relating to basal ganglia functioning?

A

Normal basal ganglia output is maintained by balanced activity in the direct and indirect pathways (parallel eachother)

26
Q

What is the difference between the direct and indirect basal ganglia pathways?

A

Direct: promote movement (excitatory)

Indirect: inhibit movement (inhibitory)

27
Q

What causes Parkinson’s Disease (PD)?

A

Loss of dopaminergic neurons from SNPC so there is loss of striatum activation via D1 receptor supressing the direct pathway causing decreased movement (hypokinesis)

28
Q

What is disinhibition?

A

When an inhibitor inhibits an inhibitor so activation occurs instead (if activator is present)

29
Q

Describe the steps of direct pathway.

A
  1. Motor cortex activity excites striatum
  2. SNPC can also activate striatum via DA acting on D1 receptors
  3. Striatum activity inhibits GPI + SNPR
  4. Activity inhibits thalamus ventral anterior/lateral nucleus
  5. Activity excites motor cortex via pre/supplemental motor cortex
  6. Motor cortex promotes movement in muscles via CST/CBT
30
Q

Give an overview explanation of the direct pathway.

A

Inhibition of the inhibitory globus pallidus internus (GPI) allows the thalamus to activate the cortex

31
Q

What causes Huntingtons Disease (HD)?

A

Degeneration of striatal input to GPE via degeneration of GABAergic connection, overexciting the thalamus promoting movement (hyperkinesis)

32
Q

Give an overview explanation of the indirect pathway.

A

Inhibiting the inhibitory GPE enables the STN to activate the GPI which in turn inhibits the thalamus resulting in less cortical activation

33
Q

Describe the steps of the indirect pathway.

A
  1. Cortex activity excites striatum
  2. Striatum activity inhibits GPE
  3. GPE activity inhibits STN
  4. STN activity excites GPI + SNPR
  5. GPI/SNPR activity inhibits thalamus ventral anterior/lateral nucleus
  6. This activity excites cortex via pre/supplemental motor cortex
  7. Cortex reduces movement of muscles vis CST/CBT
34
Q

Generally what characterizes hyperkinetic and hypokinetic disorders?

A

Hyperkinetic: underactivity of GPI

Hypokinetic: overactivity of GPI

35
Q

What surgical technique can be used in Parkinson’s Disease (PD)?

A

Removal of GP

36
Q

What can cause the indirect pathway to promote movement?

A

SNPC can inhibit the striatum via DA acting on D2 receptors

Block 3 (40 decks)

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