Basal Ganglia

Question 1

What are the major divisions of the basal ganglia:

Answer 1

Striatum (caudate, putamen and nucleus accumbens)
Globus Pallidus (external and internal segments)
Subthalamic Nucleus
Substantia Nigra (compact and reticular parts)

Lenticular/Lentiform Nucleus refers to the globus pallid us and putamen

Question 2

Function of the striatum:

Answer 2

Receive input from the cortex (always excitatory), relays it to the globus pallidus.

Question 3

What part of the basal ganglia communicates with the thalamus?

Answer 3

Only the globus pallidus internal communicates with the thalamus. It has a tonic inhibitory effect.
Direct pathway: normall inhibits the GPi, decreasing the inhibition on the thalamus
Indirect pathway: normally and eventually will excite the GPi, which will then inhibit the thalamus.

Question 4

What is the components and role of the Substantia Nigra?

Answer 4

Made up of the compact part and the reticular part.

The compact part will secrete dopamine.
The reticular part has a function similar to the globus pallidus internal

located in the midbrain

Dopamine will excite the direct pathway through D1 Receptors, and inhibit the indirect pathway through D2 receptors.

Question 5

What sensory input does not go through the thalamus?

Answer 5

Smell, has its own pathway

Question 6

Explain the divisions of the globus pallidus:

Answer 6

GPi, communicates with the thalamus, through two main fiber bundles- lenticular fasciculus and ansa lenticularis, which bundle up again to enter the thalamus.

GPe, communicates to the subthalamic nucleus, normally inhibiting its function. (STN goes back and communicates with CPI)

Question 7

Explain the divisions of the substantia nigra nucleus:

Answer 7

Two divisions: compacta and reticular.

The compacta releases dopamine that will excite/inhibit the striatum, depending if it is internal/external.

The reticular has a function similar to the GPi; releases dopamine that will inhibit the thalamus.

Question 8

What is the principle neurotransmitter used between from the cortex to the striatum?

Answer 8

excitatory through glutamate

Question 9

What is the principle neurotransmitter used between the BG and thalamus?

Answer 9

GABA, through the GPi and SNr