Term
| What is the major DA input into the Basal Ganglia? |
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Definition
Substantia Nigra pars compacta (SNpc)
- Projects D1 (increase cAMP) and D2 (decrease cAMP) to striatum, which consists of Putamen, Caudate nucleus and Nucleus Accumbens. |
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Term
| What are the major output nuclei for the Basal Ganglia? |
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Definition
1) Substantia Nigra pars reticularis (SNpr)
2) Globus Pallidus internus (GPi)**
- Get inhibitory input (GABA) from the Striatum (direct path) and excitatory input (Glutamate) from the Subthalamic nuclus (indirect path)
- Send inhibitory input (GABA) into VL/VA motor thalamic nuclei, which send excitatory input (Glutamate) into Cortical Motor Areas. |
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Term
| What is the "limbic channel" of the basal ganglia? |
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Definition
Limbic regulation of emotions, memory, motivation ect.
1) Sources of input
- VTA (DA)
- Temporal CTX/Hippocampus/Amygdala
2) BG input nuclei
- Nucleus Accumbens **
- Ventral Caudate/Putamen
3) BG output nuclei
- Ventral pallidum**
- GPi/SNpr
4) Thalamus
- Mediodorsal**
-Ventral anterior
5) Cortex
- Anterior Cingulate
- Orbitofrontal
- Medial temporal cortex. |
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Term
| What is the "Prefrontal channel" of the basal ganglia? |
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Definition
Subserves Cognitive Processes
1) Sources of input
-Posterior parietal CX
-Premotor CX
2) BG (in)
- Caudate head
3) BG (out)
- GPi/SNpr
4) Thalamus
-Mediodorsal/VA
5) Cortex
- Prefrontal |
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Term
| What is the "Oculomotor channel" of the basal ganglia? |
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Definition
High oculumotor functions such as Smooth pursuits (Posterior parietal CX) and Saccades (Prefrontal CX)
1) Sources of input
- Posterior Parietal CX (smooth pursuit)
- Prefrontal CX (saccades)
2) BG (in)
- Caudate body
3) BG (out)
- GPi/SNpr (BG output)
4) Thalamus
- VA/MD
5) Cortex
- Frontal eye fields
- Supplementary Eye fields |
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Term
| What is the "Motor channel" of the basal ganglia? |
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Definition
Affects descending motor tracts without actually projecting to the periphery (hyperkinetic and hypokinetic movements)
1) Sources of Input
- S1/M1/Premotor (input)
2) BG (in)
- Putamen
3) BG (out)
-GPi/SNpr
4) Thalamus
- VL/VA
5) Cortex
-Premotor
-Supplementary motor |
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Term
| What are the major inputs to the BG? |
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Definition
1) Thalamus (internal medullary lamina)
2) Cerebral Cortex
3) SNpc
Received by caudate and putamen |
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Term
| What structures make up the "lentiform nucleus" and the "striatum"? |
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Definition
1) Lentiform nucleus= Putamen + Globus Pallidus
2) Striatum= Caudate nucleus + Putamen + Nucleus Accumbans |
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Term
| What are the 2 main GPi output pathways to the thalamus that occur in the 4 functional BG channels? |
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Definition
Both converge on Pre-rubral field and then enter Thalamic nuclei.
1) Ansa Lenticularis (Loops UNDER internal capsule)
2) Lenticular Fasciculus (Penetrates internal capsule) |
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Term
| What is the differential role of D1 and D2 dopamine receptors in the Striatum in terms of Basal Ganglia circuitry? |
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Definition
Both receptors are excited by DA input from SNpc and lead to Cortical excitation in the motor channel of the BG.
1) D1 leads to increase cAMP and activation of direct pathway
2) D2 leads to decreased cAMP and inhibition of indirect pathway |
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Term
| How might losing D1 and D2 stimulation in PD lead to hypokinetic movements like Bradykinesia? |
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Definition
1) D1 is direct pathway
- Lack of D1 excitation in Striatum means lack of inhibition of GPi/SNpr
- GPi/SNpr effectively inhibits Ventral thalamus, which cannot excite the cortex.
2) D2 is indirect pathway
- Lack of D2-mediated inhibition of Striatum means more GPe inhibition
- GPe cannot inhibit STN, which excites GPi/SNpr
- GPi/SNpr inhibits Ventral thalamus and prevents cortical activation. |
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Term
| What are the 3 primary types of Hypokinetic movements and how can they be distinguished? |
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Definition
Bradykinesia, Akinesia, Rigidity
1) Bradykinesia= slow movement with reduced amplitude
2) Akinesia= no movement
3) Rigidity= increased tone
- Spasticity (UMN abnormality)
- Cog-wheeling (Extrapyramidal BG issue)
- Lead-Pipe (Extrapyramidal BG issue) |
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Term
| Distinguish between the 3 types of muscle Rigidity. |
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Definition
Velocity dependence (Spasticity vs. Cog-wheel & Lead-pipe), Pyramidal involvement (Spasticity vs. Cog-wheel and Lead-pipe) and Weakness/Atrophy (Only Spasticity)
1) Spasticity
- Pyramidal, UMN issue
- Velocity-dependent, weakness of arm flexers and leg extensors with Atrophy due to denervation
2) Lead-Pipe
- Extrapyramidal, BG issue
- Velocity-independent activity of multiple muscles
- NO WEAKNESS OF ATROPHY
3) Cog-Wheeling
- Same as Lead-Pipe but with different motion, often at wrist. |
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