Basal Ganglia

Question 1

What is the general function of the cerebral cortex?

Answer 1

Performs “higher functions” and it also has control over motor systems

Question 2

What is the general function of the basal ganglia?

Answer 2

Basal ganglia allows movement to happen

while also prevents any unwanted movement

Question 3

What is the general function of the cerebellum?

Answer 3

Cerebellum monitors movements and makes

sure that movement is as what you want it to do

Question 4

What are the parts of the striatum?

Answer 4

Putamen
Caudate Nucleus

Nucleus Accumbens - where the caudate and putamen meet

Question 5

What are the parts of the globus pallidus?

Answer 5

Internal Segment (GPi)
External Segment (GPe)

Question 6

Why does cortex not communicate directly with the thalamus?

Answer 6

Going through the striatum and globus pallidus allow for more precise control nd communication via excitation and inhibition

Question 7

Where does the GPi communicate to?

Answer 7

Thalamus

Question 8

Where does the GPe communicate to?

Answer 8

Subthalamic Nucleus. Which projects to the GPi

Question 9

Does the basal ganglia have any inputs to the LMNs?

Answer 9

No. But the BG controls the LMN via the cerebral cortex

Question 10

What NT does the cortex use to give the striatum input? What type of input is it?

Answer 10

Glutamate.

Excitatory Input.

Question 11

What NT is generally excitatory and which is inhibitory?

Answer 11

Excite - Glutamate

Inhibit - GABA

Question 12

What is the output from the BG done through? Where does it go and what NT does it use?

Answer 12

The output is to the thalamus via the GPi and SNr (substantia nigra reticular part).

GABA

Question 13

Describe the inputs on the striatum in the direct pathway.

Answer 13

Association Cortex activates the Striatum with Glutamate.

The Substantia Nigra Compact Part releases Dopamine which activates the Striatum on the D1 receptors, but inhibits it on the D2 receptors.

Question 14

Describe the direct pathway.

Answer 14

Association Cortex activates -> Striatum inhibits -> Globus Pallidus Internal inhibits -> VA/VL Complex of Thalamus activates -> Premotor Cortex

Question 15

How is the motor cortex inhibited through the direct pathway?

Answer 15

If the inhibition of the striatum on the GPi is minimal, the GPi will have high inhibition activity on the VA/VL complex of the thalamus. This will decrease the activity of the thalamus and inhibit the premotor cortex.

Question 16

How is the motor cortex activated through the direct pathway?

Answer 16

If the activity of the striatum is maximal, meaning it is highly active via the association cortex and the SNc, it will inhibit the GPi heavily. This means, GPi’s inhibition of the VA/VL complex is minimal and the thalamus is active, activating the premotor cortex as a result.

Question 17

Describe the inputs on the striatum in the indirect pathway.

Answer 17

Association Cortex activates the Striatum with Glutamate.

The SNc releases Dopamine, which has an excitatory effect on D1 receptors and an inhibitory effect on D2 receptors on the striatum.

Question 18

Describe the indirect pathway.

Answer 18

Association Cortex activates -> Striatum (SNc sends dopamine to activate/inhibit on D1/D2 receptors) inhibits -> Globus Pallidus External inhibits -> Subthalamic Nucleus activates -> Globus Pallidus Internal inhibits -> VA/VL Complex of Thalamus activates -> Premotor Cortex

Question 19

How is the motor cortex inhibited through the indirect pathway?

Answer 19

The D2 receptors are activated and dopamine from the SNc inhibits the activity of the striatum. This inhibition allows for increased GPi activity which inhibits the VA/VL of the thalamus and inhibits the premotor cortex, preventing any unwanted movements while voluntary movement occurs.

Question 20

How is the motor cortex activated through the indirect pathway?

Answer 20

The D2 The D2 receptors are activated and dopamine from the SNc inhibits the activity of the striatum. This increases the GPe activity and the sub thalamic nucleus is inhibited and the activity of the GPi decreases. The VA/VL of the thalamus is disinhibited and the motor cortex can then be activated.

Question 21

What changes in the direct and indirect pathway occur as a result of Parkinson’s Disease?

Answer 21

The dopamine D1 and D2 receptors are degenerated which leads to diminished inhibition of the GPi from the direct pathway and an increased inhibition of the GPe.

This leads to more active sub thalamic nucleus which activates the GPi which then inhibits the VA/VL of the thalamus and inhibits movement, causing the loss of movement observed in Parkinson’s.

Question 22

What changes in the direct and indirect pathway occur as a result of Huntington’s Disease?

Answer 22

The inhibition of the GPe by the striatum is diminished which results in the GPe being very active and it inhibits both the GPi and the STN, preventing any inhibition of the VA/VL of the thalamus, leading to increased movements, often involuntary, involved in Huntington’s.

Question 23

What is the general effect of the direct pathway WITHOUT dopamine?

Answer 23

Increases motor activity

Question 24

What is the general effect of the indirect pathway WITHOUT dopamine?

Answer 24

Decreases motor activity

Question 25

What is the general effect of the direct pathway WITH dopamine?

Answer 25

Dopamine will excite the direct pathway increasing the motor activity further

Question 26

What is the general effect of the indirect pathway WITH dopamine?

Answer 26

Dopamine will inhibit the indirect pathway, which increases motor activity