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Brain and Behavior Exam 3 > Lec 33 Basal Ganglia > Flashcards

Lec 33 Basal Ganglia Flashcards

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1
Q

What are main functions of basal ganglia?

A
  • refine motor plan
  • regulate action selection
  • facilitate habit learning
  • reward seeking
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2
Q

What comprises the striatum?

A 
dorsal = caudate nucleus and putamen
caudate = medial; putamen = lateral
ventral = nucleus accumbens septi [NAS]
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3
Q

What separates caudate and putamen?

A

anterior limb of internal capsule

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4
Q

What are the major components of the basal ganglia system?

A 
neo-striatum [dorsal and ventral]
pallidum [external, internal, ventral]
substantia nigra [compacta, reticulata]
ventral tegmental area [VTA]
subthalamic nuclei
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5
Q

What comprises the lenticular nucleus?

A

putamen and globus pallidus

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6
Q

What are the striatal cell bridges?

A

cells that cross the internal capsule to link the caudate to the putamen

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7
Q

What 2 structs does the posterior limb of internal capsule separate?

A

thalamus [medial]

lenticular nucleus [lateral]

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8
Q

What are medium spiny neurons [MSNs]? function?

A

striatal projection neurons

    • cell bodies medium, dendrites have spines
    • receive major input to BG system and are major output cells of striatum
    • GABAergic
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9
Q

What are two types of medium spiny neurons?

A
  • those that co-localize substance P and have D1-like DA receptors = stimulate cAMP –> mediate post-synaptic excitation
  • those that co-localize enkephalin and have D2-like DA receptors = inhibit cAMP and post-synaptic activity
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10
Q

Where do MSNs project?

A

from striatum to globus pallidus and substantia nigra

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11
Q

What is nucleus accumbens septi?

A

major structure of ventral striatum

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12
Q

Where do major inputs to BG system arise from?

A 
cerebral cortex = but especially frontal lobe!
thalamus
midbrain
raphe nuclei
locus coeruleus
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13
Q

For each of the 5 major inputs of BG system, which type of NT?

  1. cerebral cortex
  2. thalamus
  3. midbrain
  4. raphe nuclei
  5. locus coeruleus
A
  1. cerebral cortex == glutamate
  2. thalamus == glutamate
  3. midbrain == DA
  4. raphe nuclei == 5HT
  5. locus coeruleus = NE
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14
Q

What is globus pallidus?

A

lateral to internal capsule and medial to putamen

3 parts: external, internal, ventral

dorsal pallidum = external + internal

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15
Q

What structures make up the dorsal pallidum?

A

external and internal globus pallidus together = dorsal pallidum

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16
Q

Where is ventral pallidum located?

A

ventral to anterior commissure?

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17
Q

What type of output cells of GP?

A

all GABAergic = inhibitor

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18
Q

What is the subthalamic nucleus [STN]? type of output?

A

rostral/lateral to substantia nigra

output = glutamatergic [excitatory]

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19
Q

What is substantia nigra pars compacta?

A

GABAergic
often considered part of GPi
mainly same projections
source of DA neurons to striatum MSNs

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20
Q

What is unique projection of substantia nigra pars compacta?

A

superior colliculus = coordination eye, head, neck movement

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21
Q

Where do VTA DA neurons go?

A

to ventral striatum and limbic structures and frontal lobes

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22
Q

What are VTA DA neuron dysfunction associated with?

A

schizophrenia
psychoses
drug addiction

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23
Q

Which thalamic nuclei give input directly to striatum?

A
  • ventral group [VA/VM; VL with Vop and Vim
  • intralaminar nuclei [CM]
  • medial dorsal nucleus [MD]
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24
Q

What is function of medial part of VPM?

A

taste VP-MMMMMM

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25
Sensory-motor areas of cortex send input to which parts of striatum?
putamen
26
limbic-related input from cortex goes to which part of striatum?
ventromedial part
27
Where do GABA/substance P MSNs from striatum project?
to GPi and SNr
28
Where do GABA/enkephalin MSNs from striatum project?
to GPe
29
What is the basic cortex-striatal circuit?
cortex --> BG --> internal processing --> thalamus --> back to cortex
30
What happens to SN pars compacta and VTA in parkinsons?
pars compacta DA neurons degenerate | VTA does not
31
Where does ventral striatum receive inputs from? where does it project to?
input: cortex also: amygdala, hippocampal formation, most of 5HT input to striatum output: ventral pallidum
32
What is path of ventral striatum input/output?
cortex/amygdala/hippocampus/5HT --> ventral striatum --> ventral pallidum --> STN --> thalamus
33
What is the "nigrostriatal pathway"? importance?
DA projection from substantia nigra pars compacta to striatum circuit of motor functions - degenerates in parkinsons disease
34
Where do dopaminergic projects from VTA go? function?
to ventral striatum circuit of emotions/motivation = mesolimbic reward path
35
Where does GPe primarily project?
to subthalamic nucleus
36
What is function of STN? inputs/outputs?
- receives GABAergic input from GPe and ventral pallidum - receives glutamate input from cerebral cortex - receives DA from SNpc - projects glutamate to pallidum and substantia nigra - target for deep brain stimulation
37
What are the instrinsic processing structures of basal ganglia?
- subthalamic nucleus [STN] - SNpc - VTA - GPe
38
What separates the ventral striatum from the olfactory tubercle?
anterior commissure
39
What are the cell types that exist in striatum?
projection neurons = medium spiny neurons 2 kinds --> substance P [excitatory] and enkephalin localizing [inhibitory]; both GABA interneurons = aspiny - mostly GABAergic
40
Where does dorsal striatum project to?
globus pallidus [ext and in] | substantia nigra [reticulata and compacta]
41
Where does ventral striatum project to?
ventral pallidum | ventral tegmental area [VTA]
42
What is best way to localize GPe and Gpi on picture?
start at putamen = wide part of funnel | then travel medial; next structure = external; after that all other segments are part of internal
43
What are the 3 output structures of basal ganglia? their NT?
globus pallidus substantia nigra pars reticulata ventral pallidum all GABAergic = inhibitor
44
What is function of each of the 3 BG outputs?
SNpr output = motor control of eye, head, neck GPi output = motor control of rest of body Ventral pallidum = limbic
45
Where do major outputs from BG system project?
Thalamus [VLa, VA, VM, MD, ILN] Epithelamaus/midbrain/pons - superior colliculus; pontine tegmentum
46
Via what routes do GPi/SNr output axons travel?
mainly = pyramidal motor system = lateral, fine motor control - ansal lenticularis = loops around internal capsule - lenticular fasciculus = goes through internal capsule the 2 fiber bundles join together rostral to red nucleus to form fiber bundle called "thalamic fasiculus" also = extrapyramidal = medial, postural control - some GPi/SNr output goes to prontine + medullary reticular formation to influence reticulospinal tract - SNpr projects to superior colliculus and influences tectospinal tract
47
Where do fibers in thalamic fasiculus come from?
- BG output via ansa lenticularis and lenticular fasciculus | - fibers from dentate nucleus of cerebellum
48
How does basal ganglia coordinate higher level behavioral planning
receives info from 5 parallel functional loops of cortical info that process different types of info - relay info back to thalamus and send to modulate motor planning and execution - info also looped back from thalamus to basal ganglia for further refinement
49
What type of NT in striatal, pallidal, and SNpr projections?
GABA = inhibitors
50
What type of NT in input [cortex, thalamic] to BG system?
excitatory = glutamate
51
What is direct pathway in BG system?
cerebral cortex --> excitatory MSNs with GABA/substanceP/D1 DA receptors --> inhibit GPi --> thus thalamus is disinhibited --> cortical excitation DA activates this path by acting on D1 receptors
52
What is indirect pathway in BG system?
cerebral cortex glutamate --> inhibitor MSNs with GABA/enkephalin/D2 Da receptors --> inhibit GPe --> disinhibit STN --> increases glutamatergic excitation GPi --> thalamic inhibition --> decreased cortical excitation to suppress movement DA inhibits this path by acting on D2 receptors
53
How does the STN coordinate activity of the direct/indirect BG paths?
"center-surround" system = direct path promotes desired motor programs = indirect suppresses all alternative plans one might pursue
54
How does dopamine affect balance of direct/indirect paths?
dopamine excites direct path and inhibits indirect path thus net excitatory effect on thalamus
55
How does parkinson's disease affect BG paths?
parkinsons = loss of dopamine in nigrostriatal path so less DA input to direct/indirect paths --> less excitement of direct + less inhibition of indirect --> net inhibition of thalamus
56
What is the hyperdirect path? function?
function = fast inhibitory surround cortex --> excites MSNs in striatum --> project to GPe and SNpc --> as SNpc synalse on DA projection neurons and INHIBIT them
57
What are major symptoms of PD?
- tremor - rigidity - bradykinesia
58
what is pathology of PD along direct and indirect paths?
due to degeneration of substantia nigra pars compacta DA neurons - -> loss of DAergic D1 --> disinhibition GPi --> excess inhibition thalamus - -> loss of DAergic D2 inhibition --> overactivity GABA/Enk --> inhibition GPe --> disinhibition STN-GPi --> excess inhibition thalamus
59
What is pathology of huntingtons along direct and indirect path?
atrophy of dorsal striatum = loss of striatal MSNs direct: decreased activity of GABA/subP neurons --> less disinhibition of thalamus indirect: decreased activity of GAPA/Enk neurons --> less inhibition of thalamus indirect is more affected than direct --> so balance swings toward more direct path = too much movement/excitation
60
What are main symptoms of huntingtons?
initial fidgetiness, restlessness | abrupt jerky abnormal movements

Brain and Behavior Exam 3 (32 decks)

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