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NEUR 2000 > Lecture 12: Movement II - Basal Ganglia > Flashcards

Lecture 12: Movement II - Basal Ganglia Flashcards

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1
Q

What is hyperalgesia, and what is an example?

A
  • Peripheral sensitization to pain after damage

- Increased sensitivity to temperature after sunburn

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2
Q

What does the ciliary body do?

A
  • Produces fluid to fill the front of the eye
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3
Q

What are the functions (2) of the retinal pigment epithelium?

A
  • Phagocytosis of shed outer segments

- Regeneration of the photoreceptor pigments

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4
Q

What does the lateral corticospinal innervate?

A
  • Alpha motor neurons that are important for writing
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5
Q

What is the monocular portion of the visual field represented by on the retina?

A
  • Nasal portion
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6
Q

Axons of upper motor neurons that supply lower motor neurons for skilled movements can be found in…

A
  • Lateral white matter
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7
Q

What are the horns made up of?

A
  • Grey matter/cell bodies
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8
Q

What is the white matter?

A
  • Tracts

- Lots of myelin

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9
Q

Applying a drug that increases cGMP levels in photoreceptors would cause __________ in response to photon of light.

A
  • Attenuated hyperpolarization
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10
Q

What is the basal ganglia responsible for, in general?

A
  • Initiation of intended movement and suppression of unwanted movement
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11
Q

What is the basic function of the basal ganglia?

A
  • To influence movement by regulating activity of UMNs (no direct action on LMNs)
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12
Q

When does the basal ganglia modulate UMN activity?

A
  • In anticipation of and during movement
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13
Q

What/where is the basal ganglia?

A
  • Diverse set of nuclei deep in cerebral hemispheres
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14
Q

What structures does the basal ganglia include?

A
  • Caudate nucleus (striatum)
  • Putamen (striatum)
  • Globus Pallidus (internal and external capsules)
  • Subthalamic nucleus
  • Substantia nigra
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15
Q

What are the major components that receive and process movement-related signals?

A
  • Striatum (caudate nucleus and putamen) and pallidum (globus pallidus and substantia nigra pars reticulata)
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16
Q

Where does the substantia nigra pars compacta send signals to?

A
  • Striatum
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17
Q

Where does the subthalamic nucleus send inputs to?

A
  • Pallidum
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18
Q

What do subcortical loops link?

A
  • Link most areas of cerebral cortex with UMNs in premotor and primary motor cortices via thalamus
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19
Q

What does the SNc have a strong connection with?

A
  • Dorsal striatum
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20
Q

What is the nucleus accumbens responsible for?

A
  • Reward and reinforcement
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21
Q

Describe the body movement loop?

A

Motor/premotor/somatosensory cortices -> Putamen -> Lateral globus pallidus/internal segment -> Ventral lateral and ventral anterior nuclei of thalamus -> primary motor/premotor/supplementary motor cortex

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22
Q

Describe the oculomotor loop?

A

Posterior parietal/prefrontal cortex -> Caudate (body) -> Globus pallidus/internal segment, SNr -> Mediodorsal and ventral anterior nuclei -> Frontal eye field/supplementary eye field

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23
Q

What are the 2 main input nuclei of basal ganglia?

A
  • Caudate

- Putamen

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24
Q

Where do the caudate and putamen receive projections from?

A
  • Nigrostriatal (SNc)

- Corticostriatal (parietal, frontal, temporal, occipital lobes of cortex)

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25
Where, specifically, does the caudate receive cortical projections from?
- Primarily from multimodal association cortices | - Frontal mediated eye movements (where you orient attention)
26
Where, specifically, does the putamen receive cortical projections from?
- SI, SII somatosensory cortices - Primary motor cortex - Higher order visual cortices - Auditory association cortices
27
What are medium spiny neurons?
- Have large dendrites - A lot of dendritic branching - Good example of convergence - Part of striatal internal circuitry
28
Where do medium spiny neurons receive convergent input from?
- Cortical neurons - Dopaminergic projections from SNc - Modulation via local circuit neurons
29
Where do medium spiny neurons project to?
- Other basal ganglia regions - Segregated outputs - Primarily globus pallidus and SNr
30
Where does the putamen project to?
- Internal Globus Pallidus (GPi) | - External Globus Pallidus (GPe)
31
Where does the caudate project to?
- Internal Globus Pallidus (GPi) | - Substantia nigra pars reticulata (SNr)
32
What is medium spiny neuron firing related to?
- Impending movement - Intention to move - Also related to termination/suppression of unwanted movements - Could also be related to initiation of new movement
33
What are the primary output nuclei for MSNs of striatum?
- GP and SNr
34
What type of neurons are MSNs?
- Inhibitory (GABAergic)
35
Where does the GPi project to?
- Ventral anterior and ventral lateral thalamus (VA/VL complex)
36
Where does the VA/VL complex project to?
- Upper motor neurons in motor cortex and brainstem
37
Where does the SNr project to?
- Superior colliculus - Command head/eye movements - Bypassing the thalamus
38
What type of pathways do MSNs project onto?
- Pathways with high spontaneous activity to tonically inhibit (continually suppressing) cells in the superior colliculus of thalamus - Increases inhibitory output from striatum suppresses tonic inhibition, releasing activity in superior colliculus and thalamus and allowing activation of UMNs
39
What happens when the striatum is at rest?
- Globus pallidus is tonically active - VA/VL complex of thalamus is inhibited - There is no excitation of motor cortex
40
What happens when the striatum is transiently excited?
- Globus pallidus is transiently inhibited - VA/VL complex of thalamus is disinhibited so other inputs can excite it - Leads to excitation of motor cortex
41
What is the direct pathway?
- Release of thalamocortical circuits from tonic inhibition | - Works to decrease inhibitory output from GPi to VA/VL (disinhibition)
42
What is the indirect pathway?
- Antagonizes activity of direct pathway via GPe and the subthalamic nucleus - Increases level of tonic inhibition provided by GPi - Works to increase inhibitory output from GPi to VA/VL
43
What kind of path is the D1 receptor part of?
- Direct path | - Excitatory
44
What type of path is the D2 receptor a part of?
- Indirect path | - Inhibitory
45
How do disorders of movement occur?
- Elements of basal ganglia loops are dysregulated - Motor systems cannot switch smoothly b/n initiation and termination - Movements can be a consequence of maladaptive UMN activity
46
What is the main inhibitory neurotransmitter in the adult brain?
GABA
47
Dopaminergic neurons that synapse on MSNs originate in which brain region?
Substantia nigra pars compacta
48
What is the transmitter for the medium spiny neurons of the striatum?
GABA
49
Where do SNr axons project to that globus pallidus axons do not?
Superior colliculus
50
What is Parkinson's Disease?
- Specific degeneration of dopamine projection neurons from the SNc
51
Under standard circumstances, what does release of dopamine into the striatum do?
- Increase responsiveness of direct pathway to cortical input (via D1 activation) - Decreases responsiveness of indirect pathway (via D2 activation) - Need to be able to signal MSNs
52
How does Parkinson's disease affect the direct pathway?
- Less excitation of C/P inhibition on GPi -> greater tonic inhibitory activity of GPi -> More inhibition of VA/VL -> Less activation of motor cortices
53
How does Parkinson's disease affect the indirect pathway?
- Less inhibition of C/P inhibition of GPe -> Less inhibition on STN -> Greater excitation of GPi -> More inhibition of VA/VL -> Less activation of motor cortices
54
Once behaviour has been initiated, what might UMNs be able to do?
- Maintain behaviour without input from basal ganglia
55
What is the effect of cycling in some Parkinson's patients?
- Improvement in motor function that lasts for weeks | - Perhaps strengthening circuitry between UMNs and LMNs
56
What is Huntingdon's disease?
- Initially specific degeneration of striatal MSNs that project to the GPe that gradually atrophies the entire caudate and putamen
57
What is the effect of Huntingdon's disease in the basal ganglia?
- Loss of inhibitory C/P MSN projections to GPe -> Greater inhibition on STN -> Less excitation on to GPi and increased direct inhibition from GPe -> Less inhibition of VA/VL -> More activation of motor cortices - UMNs can be activated by inappropriate signals without influence of basal ganglia
58
What is hyperkinesis?
- Too much unwanted movement
59
Which cortices send input to basal ganglia?
- Motor - Association - Sensory
60
Afferents that go to putamen come from where?
- Motor and sensory cortices
61
What pathway are movements facilitated through?
- Direct pathway
62
Which pathway are competing movements inhibited through?
- Indirect pathway
63
Where is the caudate nucleus located?
- Floor of anterior horn of lateral ventricle
64
Where is the substantia nigra located?
- Cerebral peduncles of midbrain
65
Where do dopaminergic neurons project to?
- Caudate/putamen | - Influence motor output
66
What does the subthalamic nucleus act as?
- Pacemaker for basal ganglia circuitry through inhibitory influences

NEUR 2000 (10 decks)

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