Basal Ganglia

Question 1

What structures make up the basal ganglia?

Answer 1

• Caudate nucleus
• Putamen
• Globus pallidus (internus and externus)
• Subthalamic nucleus
• Substantia nigra

Caudate + Putamen = Striatum
Putamen + GP = Lentiform

Question 2

What structures make up the Lentiform nucleus?

Answer 2

• Putamen
• Globus Pallidus (internus + externus)

Question 3

What structures make up the striatum?

Answer 3

Putamen (motor) + Caudate (cognitive)

Question 4

What neurons are excitatory and what are inhibitory in the basal ganglia?

Answer 4

• Glutamate: Excitatory
• GABA: Inhibitory

Question 5

What pathway initiates movement?

Answer 5

Direct pathway (disinhibiting thalamic control of motor planning)

Question 6

What pathway terminates movement?

Answer 6

Indirect

Question 7

What does the substantia nigra do?

Answer 7

Inhibits the thalamus (inhibiting movement)

Question 8

How does dopamine affect the direct pathway?

Answer 8

D1 receptors
- Excites neurons
- Increases movement

Question 9

How does dopamine affect the indirect pathway?

Answer 9

D2 receptors
- Inhibits the neurons
- Decreases activity of indirect pathway
- Decreases termination of movement
- Initiates movement

Question 10

What structure in the BG inhibits the thalamus and thus inhibits movement?

Answer 10

Substantia Nigra

Question 11

What structure inhibits the substantia nigra? (meaning it does not inhibit the thalamus = More MOVEMENT) (direct pathway)

Answer 11

Striatum

Question 12

What structure excites the substantia nigra? (meaning the SN inhibits the thalamus to a greater degree = LESS movement) (Indirect pathway)

Answer 12

Subthalamic nucleus

Question 13

What is the subthalamic nucleus influenced by? (indirect pathway)

Answer 13

Inhibited by the Globus Pallidus Externis which is in turn inhibited by the Striatum
- Overall the Subthalamic nucleus EXCITES the Substantia nigra

Question 14

How is the substantia nigra influenced in the direct pathway?
- Is the SN inhibited or stimulated?
- What structure does this stimulating/inhibiting?

Answer 14

Inhibited by the striatum therefore it cannot inhibit the thalamus =>
- Thalamus is more powerful and abke toi initiate movement

Question 15

In what pathway is the substantia nigra inhibited?

Answer 15

Direct (this will mean it cannot inhibit the thalamus so the thalamus is excited = More Movement)

Question 16

In what pathway is the substantia nigra excited?

Answer 16

Indirect
- This will inhibit the thalamus thus inhibiting movement

Question 17

What is the effect of dopamine on movement?

Answer 17

Increases movement

Question 18

What inhibits the substantia nigra (direct pathway)?

Answer 18

Striatum

Question 19

What stimulates the substantia nigra (indirect pathway)?

Answer 19

Subthalamic nucleus

Question 20

What is the subthalamic nucleus inhibited by? (indirect pathway)

Answer 20

Globus pallidus externus (inhibted by striatum, so overall it is stimulated to stimulate the substantia nigra)

Question 21

What structures are invloved in the indirect pathway but not the direct?

Answer 21

• Globus pallidus externa
• Subthalamic nucleus

Question 22

What does the striatum release?

Answer 22

GABA (inhibits)
- both GPi/SN (direct) and GPe (indirect)

Question 23

Outside of the motor cortex which stimulates the striatum (caudate nucleus + Putamen) what other basal ganglia structure releases glutamte (stimulates)?

Answer 23

Subthalamic nucleus (stimulates SN)