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Flashcards in basal ganglia Deck (17)
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1
Q
4 basal ganglia
A
1. Caudate and putamen (collectively the striatum)
2. Globus pallidus
3. Substantia nigra
4. Subthalamic nucleus
2
Q
function of basal ganglia
A
1. play a role in modulation of movement (along with the cerebellum).
2. serve as a feedback look to the ipsilateral motor and association cortices.
3. lots of NT synthesis in brain
3
Q
BG is NOT involved in
A
sensation or muscle strength
4
Q
input to BG
A
Input to the basal ganglia comes from the cerebral cortex. Input comes into the caudate and putamen and then flows to the globus pallidus.

5
Q
Output of BG
A
Information flows out from the basal ganglia through the globus pallidus.
This output from the basal ganglia is also to the cerebral cortex via the thalamus.
There are no direct connections between the basal ganglia and the sensory system or the spinal motor apparatus.
6
Q
Parkinson disease characteristic signs
A
1. Resting tremor (3-6 Hz) lost during intended movement
2. Increased muscle tone
3. Difficulty with movement initiation
4. Bradykinesis
5. Shaking movements of head
6. Tremulous speech
7. Little change in facial expression
8. Difficulty making “predictive” movements
7
Q
Is the output of the basal ganglia inhibitory or excitatory?
A
The spontaneous output from the globus pallidus of the basal ganglia is inhibitory. Excitation of the caudate or putamen by the cerebral cortex can remove this inhibition.
8
Q
Parkinson etiology
A
1. loss of dopamine neurons in the substantia nigra.
2. excitation of the striatum disinhibits the motor cortex.
3. Parkinson’s patients have reduced disinhibition due to low dopamine levels, making movement initiation more difficult.
9
Q
Substantia nigra pars compacta receives input from _____ and send output______
A
caudate and putamen

back to these ganglia via dopamine containing neurons.
10
Q
Substantia nigra pars reticulata receives input from ____ and sends outputs to the ____.
A
caudate and putamen

thalamus
11
Q
Subthalamic nucleus receives input from the_____ and sends output to the _____
A
external segment of the globus pallidus

internal and external segment of the globus pallidus.

12
Q
In the absence of cortical input, the globus pallidus
A
fires spontaneously, inhibiting the thalamus.

With cortical excitation of the caudate and putamen, this inhibition is inhibited and the cortex becomes disinhibited to allow for movement.
13
Q
Huntington disease genetics
A
autosomal dominant mutation of the short arm of chr. 4 in the Huntington gene.

The mutation involves an excess of CAG triplet-repeats (40+ versus the normal 17-34 repeats).
14
Q
“Glutamate excitotoxicity” in Huntington’s patients leads to _____.
A
degradation of cholinergic and GABA-ergic striatal neurons.

As a result, the effects of the striatum on the globus pallidus are lost.
15
Q
Huntington patients choreic movements are more severe with _____.
A
either L-dopa or anti-cholinergic administration
16
Q
Why does a stroke in the subthalamic nucleus cause hemiballismus?
A
1. The internal segment of the globus pallidus is normally excited by the subthalamic nucleus.
2. Loss of excitation by the subthalamic nucleus results in reduced inhibitory outflow from the globus pallidus.
3. Reduced inhibitory outflow leads to inappropriate excitation of the motor cortex through the thalamus and flailing movements result.
17
Q
What type of stimulus (depolarizing or hyperpolarizing) would you predict would be used for the “deep stimulation” treatment of Parkinson patients?
A
Hyperpolarizing

Inhibition of the subthalamic nucleus leads to decreased excitation of the globus pallidus and decreased inhibition of the cortex.

Deep brain stimulation of the globus pallidus would need to be hyperpolarizing as well in order to inhibit the inhibition of the cortex.