Task 2 - Basal Ganglia

Question 1

Parts of the Basal Ganglia

4 with subsections

Answer 1

1. Striatum (Caudate and Putamen)
2. Globus pallidus (internal and external)
3. Subthalamic nuclei
4. Substantia nigra (compacta and reticulata)

Question 2

Medium spiny neurons

Answer 2

Aclass of cells in the striatum, whose dendrites are the destinations of the incoming axons from the cerebral cortex

Question 3

Input zone of the Basal Ganglia

Answer 3

The Striatum (Caudate and Putamen)

Question 4

Output zone of the basal ganglia

Answer 4

Globus pallidus and SNPR (Substantia nigra par reticulata)

Question 5

Direct pathway

Answer 5

1. Start in striatum, which gets information from SNPC and cerebral cortex
2. Immediately to Globus pallidus internal (inhibitory effect)
3. GPi then send to VA/VL complex of thalamus (inhibitory)
4. VA/VL complex sends to motor cortex (excitatoryI

Question 6

Indirect pathway

Answer 6

1. Striatum sends to Globus pallidus external
2. GPe sends to GPi and Subthalamic nucleus (inhibitory)
3. Subthalamic nucleus sends to GPi (excitatory, glutamate) and receives information from cortical neurons

Question 7

Prefrontal loop

4 steps

Answer 7

1. Dorsolateral prefrontal cortex
2. Anterior caudate
3. GPi, SNPR
4. Mediodorsal and ventral anterior nuclei and back

Question 8

Limbic loop

Answer 8

1. Amygdala, hippocampus, orbitofrontal anterior cingulate, temporal cortex
2. Ventral striatum
3. Ventral pallidum
4. Mediodorsal nucleus and back

Question 9

Dopamine in the basal ganglia

Answer 9

The medium spiny neurons of the striatum project directly to substantia nigra pars compacta (SNPC), which in turn sends widespread dopaminergic projections back
to the medium spiny neurons

Question 10

Duality of dopaminergic input into basal ganglia

Answer 10

• The same SNPR neurons can provide excitatory inputs to the spiny cells that project to the internal globus pallidus (direct pathway) and inhibitory inputs to the spiny cells that project to the external globus pallidus (indirect pathway).
• This duality is achieved by the differential expression of 2 types of dopamine receptors by the spiny neurons - D1 and D2 receptors.

Question 11

D1 receptors

Answer 11

D1 receptor mediate the actrivation of G-proteins that stimulate cAMP

Question 12

D2 receptors

Answer 12

D2 receptors activate G-protein that inhibit cAMP

Question 13

Parkinson’s disease

Answer 13

Characterized by tremor at rest, slowness of movement, rigidity of the extremities and neck, minimal face expression; caused by the loss of dopaminergic neurons in the SNPC

Question 14

Huntington’s disease

Answer 14

A hyperkinetic disorder, in which medium spiny neurons that project to the external segment of the globus pallidus
degenerate.

Question 15

Center surround theory of basal ganglia functioning

Answer 15

1. Activation of indirect pathway excites peripheral area of GPi via subthalamic nucleus and makes inhibition of competing movements to VA/VL complex stronger
2. Activation of direct pathway inhibits focal area of GPi which stops surpressing wanted movement in the focal point of the VA/VL

Question 16

Basal Ganglia as a gatekeeper

Answer 16

• Direct and indirect pathway have opposite effect on movement
• Basal ganglia has a role in initiating action by letting the strongest one that can break through the baseline inhibition thorugh