Basal Ganglia

Question 0

What are the structural components of the basal ganglia?

Answer 0

Caudate nucleus 
Putamen
Globus pallidus
Subthalamic nucleus
Substantia nigra

(Amygdala and nucleus accumbens)

Question 1

What are the main functions of basal ganglia?

Answer 1

Provides a feedback mechanism to cerebral cortext for initiation and control of motor responses - program sequence of movement
Augment or diminish cortical stimulation relayed by thalamus
Facilitates wanted movements and inhibits unwanted movements

Question 2

What structures combine to form the neostriatum?

Answer 2

Caudate nucleus and Putamen

Question 3

The globus pallidus is divided into two parts, what are they?

Answer 3

Globus pallidus par interna

Globus pallidus par externa

Question 4

The substantia nigra is divided into 2 parts, what are they?

Answer 4

Substantia nigra pars reticulata

Substantia nigra pars compacta

Question 5

What does the substantia nigra pars compacta contain?

Answer 5

Dopaminergic neurons

Neuromelanin - dark stain

Question 6

What does the substantia nigra pars reticulata contain?

Answer 6

Multipolar GABAergic neurons (inhibitory)

Question 7

What are the arteries that supply the basal ganglia?

Answer 7

Medial/lateral lenticulo-striate arteries
Anterior choroid artery
Penetrating branches of posterior cerebral artery

Question 8

Describe the direct pathway of initiation of movement from the cortext to the cortical motor areas.

Answer 8

Cortex stimulates the neostriatum by releasing glutamate
Stimulation allows the neostriatum to inhibit the globus pallidus interna and substantia nigra reticulata by the release of GABA, dynorphin and substance P
GPi/SNr are unable to inhibit the thalamus
Disinhibition if the thalamus allows the thalamus to stimulate the cortical motor areas to initiate movement

Question 9

Describe the indirect pathway that results in inhibition of movement.

Answer 9

Cortex stimulates the neostriatum by releasing glutamate
Stimulation allows the neostriatum to inhibit the globus pallidus externa by the release of GABA and enkephalin (Enk)
GPe is unable to inhibit the subthalamic nucleus (by GABA)
Disinhibition of the STN allows stimulation of the globus pallidus interna by the release of glutamate
Stimulation of the GPi allows for inhibition of the thalamus (GABA released)
Thalamus cannot stimulate the cortical motor areas to initiate movement

Question 10

What is the role of the substantia nigra?

Answer 10

Release of dopamine from dopaminergic neurons from the SNc has an excitatory effect on direct pathway and inhibitory effect on indirect pathway