basal ganglia

Question 1

4 basal ganglia

Answer 1

1. Caudate and putamen (collectively the striatum)
2. Globus pallidus
3. Substantia nigra
4. Subthalamic nucleus

Question 2

function of basal ganglia

Answer 2

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

Question 3

BG is NOT involved in

Answer 3

sensation or muscle strength

Question 4

input to BG

Answer 4

Input to the basal ganglia comes from the cerebral cortex. Input comes into the caudate and putamen and then flows to the globus pallidus.

Question 5

Output of BG

Answer 5

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.

Question 6

Parkinson disease characteristic signs

Answer 6

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

Question 7

Is the output of the basal ganglia inhibitory or excitatory?

Answer 7

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.

Question 8

Parkinson etiology

Answer 8

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.

Question 9

Substantia nigra pars compacta receives input from _____ and send output______

Answer 9

caudate and putamen

back to these ganglia via dopamine containing neurons.

Question 10

Substantia nigra pars reticulata receives input from ____ and sends outputs to the ____.

Answer 10

caudate and putamen

thalamus

Question 11

Subthalamic nucleus receives input from the_____ and sends output to the _____

Answer 11

external segment of the globus pallidus

internal and external segment of the globus pallidus.

Question 12

In the absence of cortical input, the globus pallidus

Answer 12

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.

Question 13

Huntington disease genetics

Answer 13

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).

Question 14

“Glutamate excitotoxicity” in Huntington’s patients leads to _____.

Answer 14

degradation of cholinergic and GABA-ergic striatal neurons.

As a result, the effects of the striatum on the globus pallidus are lost.

Question 15

Huntington patients choreic movements are more severe with _____.

Answer 15

either L-dopa or anti-cholinergic administration

Question 16

Why does a stroke in the subthalamic nucleus cause hemiballismus?

Answer 16

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.

Question 17

What type of stimulus (depolarizing or hyperpolarizing) would you predict would be used for the “deep stimulation” treatment of Parkinson patients?

Answer 17

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.