Basal Ganglia

Question 1

extrapyramidal refers to which specific regions of the brain?

Answer 1

primarily basal ganglia, including caudate and putamen nuclei, globes pallidus, substantial nigra, and hypothalamic nucleus

Question 2

the caudate and putamen nuclei merge anteriorly at the ____ _____

Answer 2

nucleaus accumbens

Question 3

the globus pallidus is directionally ____ to the putamen

Answer 3

medial

Question 4

in the direct pathway, the effect of the striata (caudate + putamen ) nuclei on the thalamus is:

Answer 4

dysinhibition (inhibits the inhibitory internal globus pallidus)

Question 5

in the direct pathway, the effect of dopamine from the substantial nigra on the thalamus is:

Answer 5

dysinhibition (excites caudate/putamen nuclei)

Question 6

how do the direct and indirect pathways differ?

Answer 6

direct: excitatory on thalamus
indirect: inhibitory to thalamus
indirect: inhibition of external globus pallidus inhibits subthalamus which tonically excites the internal globus pallidus. Therefore, inhibition of external globus pallidus results in excitation of internal globus pallidus, which results in inhibition of thalamus.

Question 7

the only areas of the cerebral cortex that don’t have input to the striatum are the:

Answer 7

primary visual and auditory cortices

Question 8

dopamine acts on the direct pathway via ___ receptors and on the indirect pathway via ____ receptors, resulting in the same effect:

Answer 8

direct - D1
indirect - D2
excitatory

Question 9

the occulomotor loop from the basal ganglia projects, in part, through the pars reticulata region of the globus pallidus to reach the _____

Answer 9

superior colliculus.

Question 10

the motor loop of the basal ganglia projects through which striatum?

Answer 10

putamen

Question 11

the occulomotor loops of the basal ganglia projects through which striatum?

Answer 11

caudate nucleus

Question 12

in contrast to the effect of dopamine on the striatum of the direct and indirect pathways, dopamine in the ventral loop (limbic system) acts on which type of receptors?

Answer 12

D3/D4

Question 13

diagram the ventral/limbic system loop:

what is the overall effect?

Answer 13

limbic cortex > nucleus accumbens of the striatum –| ventral pallidum of the globus pallidus –| mediodorsal nucleus of the thalamus > limbic (orbital + medial ) prefrontal cortex.
mood/behavioral regulation

Question 14

diagram the effect of dopamine on the limbic loop:

Answer 14

VTA ventral tegmental area > dopamine > D3/D4 receptors in nucleus accumbuns of striatum

Question 15

diagram the effect of dopamine on the direct pathway:

Answer 15

substantia nigra > dopamine > d1 receptors in the striatum

Question 16

Compare and contrast Huntington’s disease and Parkinson’s:

Answer 16

Parkinson’s: loss of excitatory input from dopamine on striatum. symptoms: tremor, difficulty initiating movement
Huntington’s: excess excitation due to degeneration of inhibition from striatum to globus pallidus. symptoms: hyperkinesias, chorea, jerky writhing movements

Question 17

describe center-surround inhibition:

Answer 17

in functioning cortex, “surround” is maximally inhibited and center is uninhibited to produce targeted, intentional movement. In choreas, tics, etc, surround is uninhibited in patches or rings, producing undesired, unintentional movement.