Friday 2 - Ruff - Basal Ganglia

Question 1

general function of basal ganglia

Answer 1

selecting between mutually exclusive actions

default is that the basal ganglia is doing nothing.

when basal ganglia does something, it is inhibition.

Question 2

parts of basal ganglia

corpus striatum

Answer 2

made of

Caudate nucleus
Putamen

contains GABA/enk (D2) - inhibited by DA - inhibits GPe
and GABA/sP (D1) - activated by DA - inhibits SNr and GPi

gets a lot of input from external sources

Question 3

parts of basal ganglia

Palladum

Answer 3

made of

globus pallidus external and internal segments

Substantia nigra reticulata

Recieves input from the striatum, and is also the basal ganglia output.

Question 4

parts of basal ganglia

subthalamic nucleus

Answer 4

directly stimulates globus pallidus internus

only excitatory nucleus in the reticular formation.

involved in the hyperdirect basal ganglia pathway (gets stimulated by the cortex

Question 5

parts of basal ganglia

substantia nigra compacta

Answer 5

Projects dopaminergic neurons to the striatum

fires tonically

also fires in bursts in response to unexpected events (involved in learning associations, maybe)

linked to dopamine reward system

generally inhibits motor output

Question 6

input to the pallidum

Answer 6

corpus striatum, mostly the ipsilateral cortex (make of the caudate nucleus and putamen)

Question 7

Neurons that make up most of the striatum

Answer 7

medium spiny neurons

Question 8

3 main pathways of the basal ganglia.

Answer 8

Direct - disinhibits a selected action, allowing it to occur

Indirect - inhibits actions other than the one selected

hyperdirect - suppresses all movement

Question 9

parts of the basal ganglia that are TONICALLY active/inactive

Answer 9

inactive-
striatum

active-
globus pallidus

Question 10

what tonically inhibits the thalmus

Answer 10

globus pallidus internal

Question 11

what actively inhibits the globus pallidus internal

Answer 11

striatum

Question 12

what excites the striatum

Answer 12

cortex,

dopamine from the substantia nigra compacta excites the GABA/sP (D1) receptors

Question 13

What inhibits the sub thalamic nucleus

Answer 13

globus pallidus externa

Question 14

only 2 excitatory pathways within the basal ganglia

Answer 14

sub thalamic nucleus

stimulates the globus pallidus internal (this ends up inhibiting motion)

substantia nigra compacta

stimulates GABA/sP (D1) receptors using dopamine

Question 15

two types of medium spiny neurons.

Where are they located

Answer 15

Located in the striatum

GABA / substance P

• project to GPi and Substantia nigra reticulata (SNr).
• direct pathway
• D1 dopamine (DA) receptors
• excitatory response to DA

GABA / enkephalin

• project to GPe
• indirect pathway
• D2 dopamine receptors
• inhibitory

Question 16

What happens if you get rid of the subthalamic nucleus?

Answer 16

Ballismus - flinging and flailing of contralateral arm

More movement because the hyperdirect pathway doesn’t work, and the STN also no longer participates in the indirect pathway

(the STN excites the GPi, which stop motor movement)