10 Basal Ganglia II

Question 1

what are the main inputs to the basal ganglia? what about outputs?

Answer 1

inputs: striatum
outputs: globus pallidus, SNR

Question 2

in the resting state, what does the basal ganglia do the the thalamus?

Answer 2

The basal ganglia suppress movement by inhibiting the thalamus and ultimately the cortex

Question 3

What is the function of the internal basal ganglia circuits?

Answer 3

to connect the input side (striatum) to the output sides (GPi and SNR)

Question 4

what are the two basic circuits called in the basal ganglia?

Answer 4

direct and indirect (This is what allows the striatum to work on the GPi and SNR)

Question 5

In general, the direct pathway of the basal ganglia is to? and the indirect pathway is to what?

Answer 5

direct pathway= bringing about wanted movements

indirect pathway= suppressing unwanted movements

Question 6

Describe the pattern of the direct pathway of the basal ganglia?

Answer 6

1) striatum (caudate nucleus and putamen)
2) D1 receptors on MSN (substance P and dynorphin)
3) GPi/SNR
4) Thalamus
5) cerebral cortex
6) Motor action

Question 7

which two areas have a major effect on the D1 and D2 receptors of the MSN’s?

Answer 7

Cortex (directly from brain)

SNC (releasing dopamine)

Question 8

what are the differences between MSN’s that are activated by the D1 vs D2 receptors?

Answer 8

MSN’s start in the striatum and go to the GPi (direct) or to the GPe (indirect). Those going to the GPi contain substance P and dynorphin (D1 receptors), and those going to the GPe contain enkephalin (D2 receptors).

Question 9

What activates the D1 and D2 receptors? where does this stuff come from?

Answer 9

1) dopamine

2) SNC

Question 10

MSN’s projecting to the GPe are inhibitory/excitatory?

Answer 10

inhibitory. They prevent the inhibition of the of the STN by inhibiting the inhibitor.

Question 11

what is the indirect pathway of the basal ganglia?

Answer 11

1) striatum
2) D2 receptor on MSN (enkephalin)
3) GPe
4) Subthalamic nuclei (STN)
5) GPi
6) Thalamus (VA)
7) Cerebral cortex
8) motor action

Question 12

What is the key monoaminergic transmitter in basal ganglia function?

Answer 12

Dopamine

note that seratonin and norepinephrine also have a small affect

Question 13

when mentioned in the notes as the striatum, what is generally being referred to?

Answer 13

putamen and caudate nucleus

Question 14

what is the nigrostriatal pathway?

Answer 14

the pathway of dopamine release from the SNC to the caudate nuclei and putamen.

Question 15

where do most axon terminals end of the dopaminergic axons coming from the SNC?

Answer 15

on the dendrites of the MSN in the striatum. (some end on interneurons)

Question 16

T/F the globus pallidus, subthalmic nucleus, and SNR have dopamine input?

Answer 16

True (clarification needed here) page 3 basal ganglia 2

Question 17

dopamine released into the striatum promotes what?

Answer 17

movement!

Question 18

what does dopamine do to the D1 receptors? D2 receptors?

Answer 18

dopamine is excitatory to the D1 receptors, and inhibitory to the D2 receptors.

Question 19

If I have an idea to move, how do I get to the point where I release dopamine?

Answer 19

1) Idea in frontal cortex
2) striosomal pathway (striatum to SNC)
3) SNC to striatum through dopamine releasing neurons.
4) release of dopamine on MSN neurons in desired loop (direct and indirect)

Question 20

what is a hypokinetic disorder?

Answer 20

akinesia or the inability to move like normal

Question 21

Is Parkinsons disease hypo or hyper kinetic?

Answer 21

hypokinetic

Question 22

what causes parkinsons disease?

Answer 22

the loss of dopaminergic neurons in the SNC

Question 23

The loss of dopaminergic neurons releasing dopamine causes a decrease in dopamine being released in the striatum. What are the down stream affect of this on the direct pathway?

Answer 23

1) no dopamine=no activation of D1
2) no inhibition GPi/SNR
3) GPi/SNR can now inhibit thalamus.
4) No stimulation of cortex by thalamus

Question 24

what if you have a stroke that affects the basal ganglia? SNC?

Answer 24

This can cause parkinsons

Question 25

What drugs/chemicals can you use to treat parkinsons? Why can you use this?

Answer 25

L-dopa, because it undergoes a decarboxylation reaction to make dopamine.

Question 26

What is one of the major problems of using L dopa?

Answer 26

Its half life in the blood is very short so only very little actually is functional by the time it gets into the brain.

Question 27

What would a lesion in the GPi nucleus or neurons (pallidotomy) do for parkinsons?

Answer 27

stop the inhibition to the thalamus.

Question 28

Why is high frequency stimulation to the STN helpful in treating parkinsons?

Answer 28

it jams the signals traveling from the STN to the GPi/SNR. (Down-regulating the positive signal for thalamic inhibition from the GPi/SNR)

Question 29

What is Chorea?

Answer 29

sudden and involuntary movements of the body.

Question 30

Huntingtons disease is characterized by chorea. Why do the these patients who have a triple repeat sequence have this problem?

Answer 30

It affects the MSN neurons leading to the GPi/SNR and GPe

Question 31

Which MSN’s are most affected by Huntingtons disease? Which pathway does this affect?

Answer 31

The MSN’s containing enkephalin stemming. It affects the indirect pathway. This reduces inhibition to the thalamus causing Chorea.

Question 32

what is hemiballismus?

Answer 32

a disease that causes chorea because of a lesion in the STN.

Question 33

what is progressive supranuclear palsy?

Answer 33

degeneration of STN, SNR, and globus pallidus causing progressive palsy.