Basal Ganglia

Question 1

What are the 5 nuclei of the basal ganglia?

Answer 1

Caudate
Putamen
Globus Pallidus (internus/externus)
Subthalamic nuclei
Substantial nigra

Question 2

Describe the cortico-basal ganglia- thalamocortical loop and state the role of the thalamus and output nuclei

Answer 2

Cortex —> Caudate/Putamen —> Substantial Nigra/Globus Pallidus Internus —> Thalamus —>

Thalamus is excitatory to the cortex
The output nuclei inhibits the thalamus

Question 3

What are the differences between the two pathways that process signals through the basal ganglia?

Answer 3

Direct = excitation of the thalamus neurons
Indirect = inhibits the thalamus neurons (so they can’t excite cortex neurons)

Normal function involved a proper balance between these pathways

Question 4

What is too much/little inhibition of the basal ganglia called and give one example

Answer 4

Too much inhibition - Hypokinetic e.g. Parkinson’s

Too little inhibition - Hyperkinetic e.g. Huntington’s

Question 5

What is the second important basal ganglia motor circuit and what is it’s role?

Answer 5

Globus pallidus internus/ Substantia nigra —> Midbrain —> Reticulospinal/ Vestibulospinal tract

When the pathway is interrupted there is excessive contraction of postural muscles causing rigidity