Basal Ganglia

Question 1

what is the definition of the basal ganglia

Answer 1

refers to structures that yield movement disorders when damaged

Question 2

what is the striatum made up of

Answer 2

caudate nucleus

putamen

Question 3

what is the lentiform nucleus made up of

Answer 3

putamen

globus pallidus

Question 4

what are the two parts of the globus pallidus

Answer 4

globus pallidus interna (GPi)

globus pallidus externa (GPe)

Question 5

what part of the basal ganglia is C-shaped w/a long tail that swings laterally

Answer 5

caudate

Question 6

what part of the basal ganglia is just medial and coincides with the insula

Answer 6

putamen

Question 7

what is the key “output” of the basal ganglia and where do most of the projections go

Answer 7

globus pallidus

-thalamus

Question 8

where is the nucleus accumbens in reference to the basal ganglia structures

Answer 8

anterior, medial and inferior

only see in cross section at HEAD level of caudate

Question 9

what seperates the putamen from the GPe

Answer 9

external medullary laminae

Question 10

what does the internal medullary laminae separate

Answer 10

GPe from GPi

Question 11

the substantia nigra is apart of the basal ganglia, what part of the brainstem can it be seen in cross section

Answer 11

rostral midbrain

Question 12

the subthalamic nuclues is a part of the basal ganglia, where is it typically located in reference to the substantia nigra at midbrain cross section level

Answer 12

just on top and lateral to substantia nigra

Question 13

what are the 2 parts of the substantia nigra ?

Answer 13

Compact - densely packed pigmented neurons

Reticular - nonpigmented neurons (more lateral)

Question 14

what is the function of the compact part of substantia nigra ? What about the reticular part ?

Answer 14

Compact - DA projections to striatum

Reticular - output of Basal ganglia (like GP)

Question 15

what limb of the internal capsule separates the caudate from the lenticular nucleus

Answer 15

anterior limb

Question 16

what limb of the internal capsule separates the thalamus from the globus pallidus

Answer 16

posterior limb

Question 17

what is the broad function of the basal gangli

Answer 17

modulate cortical output especially motor control

Question 18

what are the 4 key players in the basal ganglia circuit or loop

Answer 18

cortex –> striatum –> globus pallidus –> thalamus —-> back to cortex

Question 19

what are the main inputs of the BG circuit

Answer 19

cortical afferents to striatum

Question 20

what are the main outputs of the BG circuit

Answer 20

Globus pallidus interna and reticular part of substantia nigra

Question 21

The basal ganglia circuit or motor loop cannot influence the motor cortex directly. What does this mean ?

Answer 21

It must go through the thalamus, which is not apart of the BG its apart of the diencephalon

Question 22

excitatory connections of the BG motor loop use what nuerotransmitter

Answer 22

glutamate

Question 23

inhibitory connections of the BG motor loop use what nuerotransmitter

Answer 23

GABA

Question 24

T/F in the striatum there is only one neurochemical territory

Answer 24

F, there are many nuerochemicla territories in the striatum

Question 25

expain the direct or principal circuit of the basal ganglia

Answer 25

1 - excitatory input from cortex to striatum
2 - striatum sends inhibitory output to GPi
3 - GPi sends inhibitory output to VA/VL of thalamus
4 - thalamus sends excitatory input back to cortex

Question 26

How could you manipulate the direct pathway to increase motor cortical output ?

Answer 26

Increase inhibition on GPi (GPi is now less active)

Question 27

how does increasing inhibition on GPi result in increased cortical output

Answer 27

If increase inhibition on GPi, its less active so puts LESS inhibition on thalamus = more excitation to cortex = greater output

Question 28

how would you decrease motor cortical output in the direct BG pathway

Answer 28

Increase excitation on GPi (now more active) = increased inhibition on thalamus = decreased excitation to cortex = decreased cortical output

Question 29

the degeneration of ______ leads to huntington’s disease

Answer 29

striatum

Question 30

what is the main sign of huntingtons disease

Answer 30

chorea - rapid, rigid dance like movements of face and limbs

Question 31

T/F Huntingtons disease is autosomal recessive disease

Answer 31

F, Autosomal dominant (meaning more number the repeats the faster the onset)

Question 32

what are the 2 new additional BG structures involved in the indirect BG pathway that are not a factor in the direct pathway

Answer 32

subthalamus and GPe

Question 33

explain the indirect pathway of the basal ganglia

Answer 33

1 - excitation input from cortex to
A) striatum or B) subthalamus
2 - A) striatum inhibitory to GPe = inhibition of subthalamu
B) subthalamus excitatory output to GPi
3 - GPi inhibitory output to thalamus
4 - thalamus excitatory input back to cortex

Question 34

if you decrease the output of GPe in the basal ganglia indirect pathway, what will be the result ?

Answer 34

Decrease GPe inhibitory output on subthalamus = increased excitatory output to GPi=increased inhibition on thalamus = decreased excitatory input to cortex = decreased cortical output

Question 35

if you were to increase the inhibitory output from GPe in the indirect BG pathway what would be the end result

Answer 35

decreased thalamic inhibition = increase cortical output

Question 36

in strokes it is very common for the subthalamus to be damaged, how would this affect the indirect BG pathway

Answer 36

results in less excitatory input to GPi=decreased inhibition on thalamus= excessive increased excitatory input to cortex = TOO much cortical output

Question 37

what is the dramatic movement disorder where limbs, usually on one side of the body, are flailing and rotating that is the result of a damaged subthalamus

Answer 37

hemiballismus

Question 38

hemiballismus is the result of damage to what vessel ?

Answer 38

Posterior cerebral a. (PCA)

Question 39

what is the role of the substantia nigra in the basal ganglia

Answer 39

Substantia nigra compact - sends DA input to striatum

Substantia nigra reticulata - sends output to thalamus

Question 40

what part of the substantia nigra is similar to GPi in terms of their function

Answer 40

SNr similar to GPi b/c both are main outputs to thalamus of basal ganglia

Question 41

what are the 3 cardinal features of Parkinson’s disease

Answer 41

1 - bradykinesia
2 - resting tremors
3 - rigidity
Need 2 of the 3 for diagnosis

Question 42

The loss of ______ neurons is a major characteristic of Parkinsons disease

Answer 42

Substantia nigra compacta

Question 43

How does the loss of substantia nigra compacta affect cortical output in parkinsons disease

Answer 43

no DA projections to striatum = little inhibitory output to GPi (making more active) = increased inhibitory output to thalamus = decreased excitatory input to cortex = decreased cortical output = bradykinesia

Question 44

what is the drug commonly used to treat parkinsons disease and how does it function

Answer 44

levodopa - precursor for DA so it acts to replace lost DA projections from degeneration of nigrostriatal fibers

Question 45

if you were to treat parkinsons disease through a surgical approach, what part of the brain would you destroy and why ?

Answer 45

• remove GPi

* ** removes massive inhibition on thalamus**

Question 46

if you were to treat parkinsons disease by deep brain stimulation where would you implant the electrodes in the brain ?

Answer 46

subthalamus

Question 47

if you were trying to treat parkinsons disease that affected the right limbs of the body, what side of pallidotomy would help reduce symptoms ?

Answer 47

Left side pallidotomy

L basal ganglia controls L cortex which controls contralateral musculature*