BS545 Basal Ganglia
Terms
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Fill in the Direct Basal Ganglia circuit: names of structures, excitatory or inhibitory synapse, increasing or decreasing activity, and where dopamine is used. -
See the picture. -
Fill in the Indirect Basal Ganglia circuit: names of structures, excitatory or inhibitory synapse, increasing or decreasing activity, and where dopamine is used. -
See picture. Dopamine is released by SNc. - What is the Nucleus Accumbens?
- The area where the head of the caudate appears to be continuous with the anterior part of the putamen.
- What three structures are contained within the Striatum?
- caudate nucleus, nucleus accumbens, putamen.
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What are the two parts of the Substantia nigra?
What is the histological difference between the two? -
compact part (SNc) and reticular part (SNr).
SNc - lots of cell bodies
SNr - more fibers - What is the general functional circuit within the Basal Ganglia? Indicate which output(s) are excitatory and which are inhibitory.
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Input to striatum (excitatory)
Output from Globus Pallidus (inhibitory) ==> thalamus which influences the cortex (excitatory). - What neurotransmitter is released by the SNc? How does it have an excitatory influence in one case and inhibitory in another?
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Dopamine.
Different receptors: D1 and D2 -
Give examples of two hypokinetic (negative) signs associated with basal ganglia disorders.
Are these voluntary or involuntary movements? -
Hypokinesia - decreased movements
Bradykinesia - slower movements
Voluntary movements. -
Give five examples of hyperkinetic (gain of function) signs associated with basal ganglia disorders.
Are these voluntary or involuntary? -
Dyskinesia - fragmented, incomplete movement.
Tremor - Repetitive, oscillatory
Athetosis - Slow, writhing movement (sort of rolling wrist, head, tongue, etc)
Chorea - dance like (looks like normal dance)
Ballism - violent, flinging (usually unilateral). Person might fall.
Involuntary movements. -
What is the cellular result of Parkinson's disease?
As a result, what neurotransmitter is reduced? -
Degeneration of Substantia Nigra Compacta (SNc).
Dopamine. - What is usually visible within the neurons of Parkinson's patients?
- Lewy bodies
- How are the negative signs produced in Parkinson's disease? Relate to the Direct and Indirect circuits.
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Loss of dopamine ==> shutdown direct loop ==> shutdown cortex ==> less cortical activity.
Loss of dopamin ==> loose constraint of indirect loop ==> less cortical activity. - Explain how tremor (at rest) may occur for people with Parkinson's. Theory by Guehl et al. - 1993.
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As a result of loss of dopamine, the ventral intermediate nucleus of the thalamus becomes overactive. Studies have shown that the tremor matches the frequency of firing of the VI thalamus.
Correlation between neurons in the pallidonigral circuit increases with Parkinson. "Rhythmic bursts occur in both the pallidonigral and cerebellar thalamus. Tremor may therefore occur when correlated activities turn into synchronized oscillations that spread over the cerebellular thalamus." -
Speculate what could cause rigidity in Parkinson's disease.
Theory by Pessiglione et al. 2005. - Specificity is lost in the Palldonigral circuit in PD. This loss of segregation could lead to "coselection of antagonist motor programs, resulting in muscular rigidity."
- What are four treatments (one of them experimental) for Parkinson's disease?
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L-dopa (brain converts to dopamine).
Fetal and/or stem cell transplants near the target, not in the SNc.
Leisons: GPi, part thalamus, subthalmic nucleus
Deep brain stimulation. - What is the cause of Huntington's disease?
- CAG repeats on short arm of chromosome 4.
- What are the signs of Huntington's disease?
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Hyperkinesis: chorea/athetosis.
Dementia and cognitive changes. - For Huntington's disease, what primary structure is damaged and what is the result?
- The caudate nucleus has cognitive inputs so damage to it will result in cognitive changes.
- What is hemiballismus?
- It is a condition that usually is acute and results from a stroke. The subthalamus is damaged. It results in contralateral ballistic movements.
- What is the treatment for hemiballismus?
- Little treatment. Sometimes anti-seizure meds can help.
- What is the treatment for Huntington's disease?
- Little treatment. Leisons possible. Experimentally looking at short RNA to block the bad gene.
- Because of caudate nucleus damage, what ends up being inhibited in Huntington's disease? In what loop does this occur?
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Subthalamic nucleus
Indirect loop - Name three symptoms seen with damage to the basal ganglia
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.Chorea
2.Athetosis
3.Bradykinesia
4.Rigidity
5.Resting tremor - What is athetosis and in what disease is it found?
- The symptomatic writhing motion, most often seen in HD patients.
- The caudate nucleus receives its inputs primarily from what area of the cortex? What function is affected?
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Input from Association areas.
Cognitive functions. - The putamen receives its inputs mainly from what area of the cortex?
- Motor and somatosensory.