L30 Motor Control And Disease Pt2 Flashcards
(24 cards)
Which structures influence movement indirectly by regulating the function of upper motor neurons?
Basal ganglia and cerebellum
What are the key components in the basal ganglia?
Forebrain:
- Motor cortex
- Basal Ganglia
- Ventral lateral nucleus of thalamus
Midbrain:
- Substantial nigra
What is the motor loop?
Explain the direct pathway of the motor loop
1) With no initiating cortical input, the Globus pallid is internal segment (GPi) topically inhibits the VLo
2) Input from many cortical regions converges on the striatum
3) When activated by this input, the striatum inhibits the inhibitory activity of the GPi, releasing the VLo to activate Area 6 and initiate movement
Explain the indirect pathway of the motor loop within the Basal Ganglia
1) The direct pathway is modulated by a complex indirect pathway involves the substantial nigra (SN) and GP external segment (GPe)
2) The substantia nigra acts via the striatum (CP) to maintain the balance between inhibition and activation of the BLo.
3) So the SN is balancing or ‘tuning’ the activation of the VLo
Explain how the substantia nigra maintains the balance between inhibition and activation of the VLo
- Excitatory input from the SN stimulates VLo activation, by activating the inhibition of the GPi through the direct pathway
- In the indirect pathway, the GPe inhibits the GPi
- But the GPe is inhibited by the CP -> VLo inhibition
- However, inhibitory input from the SN decreases CP inhibition of the GPe, -> GPi inhibition, thus allowing activation of the VLo
What is Parkinson’s disease?
Parkinson’s disease (PD) is the 2nd most common progressive neurodegenerative disorder that primarily affects the central nervous system, impacting both motor and non-motor functions
Is Parkinson’s disease mainly a sporadic or a familial case?
Sporadic cases (85-90%)Familial cases (10-15%) caused by genetic mutations
What are the symptoms for Parkinson’s disease?
- Hypokinesia - paucity/insufficiency of movement
- Bradykinesia - very slow movements
- Akinesia - no movements
- Increased muscle tone - rigidity
- Resting Tremor - @4-5Hz- ‘pill rolling’
- Shuffling gait and flexed posture, impaired balance
- Mask-like expression
What is Parkinson’s disease caused by?
dopamine loss due to reduction of dopaminergic neurons in the substantia nigra
What % of the brain’s dopamine is found in the basal ganglia?
80% of the brain’s dopamine is found in the basal ganglia, specifically the substantia nigra (SN)
Lewy bodies
What did Oleh Horyenkiewicz find?
He found that L-DOPA (a dopamine precursor) provided a dramatic though brief reversal of symptoms in PD patients.
Later, Cotzias showed that gradual increases in oral L-DOPA provided a significant and longer benefits
What is L-DOPA a temporary therapy?
What does reduced dopaminergic input from substantia nigra to striatum do to the direct and indirect pathways?
Explain the mechanism behind the reduced dopaminergic input that affects the pathways
What is Huntington’s disease?
What are the symptoms of Huntington’s disease?
- Early: hyperkinesia or dyskinesia, ‘chorea’ (involuntary jerking or twitching movements)
- Late: akinesia and dystonia (muscle spasms), dementia, personality disorder (psychosis)
What is the cause of Huntington’s disease?
- Autosomal dominant genetic disease resulting in neuronal degeneration:
- initially in the indirect pathway components of the striatum,
- subsequently in the direct pathway components & in the GPe
What happens early on in the basal ganglia in Huntington’s?
What happens in the later basal ganglia in Huntington’s?
What are the genetical differences between PD and HD?
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