Basal Ganglia

Question 1

Corpus striatum

Answer 1

. Caudate, putamen, and globus pallidus

Question 2

Striatum (Neostratium)

Answer 2

Caudate and putamen
. Contains neurons that use either ACh or GABA
. Most inputs to here

Question 3

Lenticular (lentiform) nucleus

Answer 3

Putamen and globus pallidus

Question 4

Globus pallidus

Answer 4

. Composed of internal and external segments
. Use GABA
. Internal segment (GPi): major output of corpus striatum projecting to VA/VL nuclei in thalamus, receives input from striatum, external globus pallidus, and subthalamus (most outputs from here)
. External segment (GPe): input from striatum, projects to internal segment and subthalamus

Question 5

Substantia nigra

Answer 5

. Ventral portion of midbrain tegmentum
. Pars compacta: dopamine, have neuromelanin to give black appearance
. Pars reticula: uses GABA
. Prinicpal source of dopamine to the striatum via nigtostriatal tract

Question 6

Sub thalamic nucleus

Answer 6

. Just ventral to thalamus

. Connected to striatum and substantia nigra

Question 7

Inputs to basal ganglia

Answer 7

. Striatum receives input from all areas of cerebral cortex, esp. premotor and supplemental motor cortices
. Project to ispsilat. Striatum via corticostriate projections

Question 8

GABAergic spiny neurons

Answer 8

. Contains many dendritic spine
. Main type of neurons involved in both direct and indirect pathway
. Activation leads to inhibition of neuromodulation of their target neurons

Question 9

Cholinergic interneurons

Answer 9

. Uses ACh
. Function to modulate local activity w/in striatum
. Constitutively active neurons

Question 10

D1 group of receptors in striatum

Answer 10

. When dopamine binds it is excitatory on postsynaptic neuron
. Plays role in direct pathway

Question 11

D2 group of receptors in striatum

Answer 11

. When dopamine binds it has inhibitory effect on postsynaptic neuron
. Plays role in indirect pathway through basal ganglia

Question 12

Striatopallidal projections

Answer 12

. Striatum projects onto GPe and GPi

. Utilize GABA and are inhibitory

Question 13

Striatonigral fibers

Answer 13

. Striatum projects to substantia nigra

. Use GABA, inhibitory

Question 14

Subthalamus nucleus projects to ____

Answer 14

. GPi

. Use Glu, excitatory

Question 15

Outputs of basal ganglia

Answer 15

. GPi main source
. Projects to VA and VL thalamic nuclei
. Pallidothalamic projections utilize GABA and are inhibitory

Question 16

Basal ganglia interconnections are ipsilateral or contralateral?

Answer 16

. Ipsilateral

. Indirect effects on cerebral cortice influence motor control of contralat. Side of body though corticospinal system

Question 17

Direct pathway

Answer 17

. Facilitates flow of info through thalamus
. Utilizes D1 group
. Thalamic activity is inc. by activation
. Cortical activity is inc. and so are movements
. Cortex to striatum fibers using Glu to excite spiny neurons D1 and turn them on
. D1 neurons send out GABA to GPi to turn off inhibitory neurons
. Disinhibition of the inhibitor neuron releases the thalamus from inhibition and allows thalamus to be activated
. Thalamic fiber to M-1 send Glu and excite neurons to inc. motor cortex firing

Question 18

Indirect pathway

Answer 18

. Inhibits flow of info through thalamus
. Uses D2 dopamine receptors
. Subthalamic nucleus is key part
. Thalamic activity and cortical activity are dec.
. Cortex sends Glu to striatopalladal D2 neurons to turn them on
. D2 sends GABA and inhibits GPe that normally inhibit subthalamus
. Nothing is inhibiting subthalamus and its glutamanergic neurons excite GPi neurons
. Inhibitory pallidothalamic neurons activate and inhibit the thalamocortical projections dec. movement
. When thalamus is inactivated it can’t activate M-1

Question 19

T/F nigral and pallidal inputs to thalamus are tonically active

Answer 19

T

Question 20

T/F D1 receptors and direct pathway is excited when dopamine is released

Answer 20

T

Question 21

Positive feedback pathway when dopamine is released

Answer 21

. D1 receptors turned on and D2 turned off
. Striatum sends GABA projections to cells in pars reticulata
. Causes further disinhibition of thalamus by inhibiting pars peticulata inhibitory neurons
. Inhibits the inhibitory projections of pars reticulata to pars compacta to enhance further dopamine release

Question 22

Parkinsonism

Answer 22

. Loss of dopaminergic inputs from striatum from substantia nigra
. Indirect system is dominant due to ACh leading to serious lack of movement

Question 23

How ACh affects pathways

Answer 23

. Excites D2 and inhibits D1 activating the indirect pathway

Question 24

Chorea

Answer 24

. Loss of cholinergic interneurons in striatum
. Direct system dominant
. Leads to excessive, unwanted movements

Question 25

T/F basal ganglia influence motor movements even though they have no direct connections to lower motor neurons

Answer 25

T