Sievert: Basal Ganglia

Question 1

What is the basic loop from the basal ganglia to the cortex?

Answer 1

basal ganglia –> thalamus –> cortex –> basal ganglia

Question 2

Do to the basal ganglia project to the same side or the opposite side?

Answer 2

always project to the contra side

Question 3

Where is the subthalamic nucleus located?

Answer 3

underneath the thalamus, rostral to the substantia nigra

Question 4

Where is the substantia nigra located?

Answer 4

in the midbrain, above the cerebral peduncles

Question 5

The striatum is considered the (blank) zone. What are its two components?

Answer 5

receiving; caudate and putamen

Question 6

What makes up the lenticular nucleus?

Answer 6

putamen and globus pallidus

Question 7

The efferent zone of the basal ganglia that consists of the globus pallidus and the substantia nigra

Answer 7

pallidum

Question 8

What are two additional nuclei that are functionally part of the basal ganglia?

Answer 8

substantia nigra

subthalamic nucleus

Question 9

What constitutes the receiving zone of the basal ganglia?

Answer 9

caudate and putamen

Question 10

How are the caudate and putamen similar and how are they different?

Answer 10

they are functionally similar in terms of their efferents, but slightly different in terms of their afferents

Question 11

In general, the striatum receives input from what areas?

Answer 11

all areas of the cortex except for the primary visual and primary auditory areas
**also gets an important input from the substantia nigra

Question 12

What makes the caudate a good receiving center?

Answer 12

It follows the lateral ventricle, so it is in a good position to receive inputs from almost all areas of cortex

Question 13

What is the end result of the direct pathway?

Answer 13

increases excitatory thalamic input to the cortex, and turns UP motor activity

Question 14

In the direct pathway, what happens from cortex to striatum? From striatum to GP? From GP to VA/VL? From thalamus to cortex?

Answer 14

excites striatum
more inhibition to GP
less inhibition to Va/Vl
Va/Vl more active
more excitation to motor cortex

Question 15

What is the end result of the indirect pathway?

Answer 15

decreases excitatory thalamic input, so turns DOWN motor cortex activity

Question 16

In the indirect pathway, what is the effect from cortex to striatum? What is the effect from striatum to external GP? What is the effect from external GP to subthalamic nuclei? What is the effect fromr subthalamic nuclei to internal GP? What is the effect from internal GP to Va/Vl? What is the effect from Va/Vl to motor cortex?

Answer 16

excitation; inhibitory; inhibitory to subthalamic nuclei; excitatory to GPi; inhibitory to Va/Vl; less output from Va/Vl = less motor cortex firing

Question 17

What is the effect of the substantia nigra on the direct pathway (D1)? What about its effect on the indirect pathway? What is the net result of both pathways?

Answer 17

turns UP the direct pathway
turns DOWN the indirect pathway
increased VA/VL drive to cortex and more motor activity

Question 18

The striatum has small (blank) which act on the two paths (direct and indirect)

Answer 18

cholinergic cells

Question 19

What effect do cholinergic cells have on the direct pathway? On the indirect pathway? What is the overall effect of these cells?

Answer 19

turn DOWN the direct pathway; turn UP the indirect pathway; decrease VA/VL drive to cortex = less motor activity

Question 20

What are the two categories of basal ganglia disorders?

Answer 20

hypokinetic

hyperkinetic

Question 21

Is Parkinson’s disease hypo or hyperkinetic? What are some symptoms?!

Answer 21

hypokinetic;
tremor at rest
masked facies
rigidity
retropulsion
festinating gait
shuffling gait
loss of postural reflexes
depression, anxiety, dementia

Question 22

Parkinson’s is a disorder due to a loss of the dopamine projecting cells from the (blank) to the (blank). The loss on the direct path is to reduce excitation of the striatum which causes a decrease in motor activity. Essentially the small ACh cells become dominant.

Answer 22

nigra; striatum

Question 23

If there is less dopamine (as seen in Parkinson’s), what affect does this have on the direct pathway?

Answer 23

reduced excitation of the striatum, which causes a decrease in motor activity (so decreased activity of the direct pathway)

Question 24

The balance between ACh and Dopamine is important. If you lose dopamine (as seen in Parkinson’s), what will happen to ACh?

Answer 24

the ACh cells will become dominant and will result in less motor activity

Question 25

What is the result of Parkinson's on the indirect pathway?

Answer 25

``` Increases the indirect pathway!! lose dopamine cells affecting D2 receptors less inhibition of the indirect pathway reduced motor output of the Va/Vl nuclei small ACh cells are dominating ```

Question 26

What are two examples of hyperkinetic syndromes?

Answer 26

Huntington's Chorea | Hemiballismus

Question 27

What is hemiballismus caused by? What is a characteristic feature of hemiballismus?

Answer 27

damage to the subthalamic nucleus; wild flinging movements of the body

Question 28

What does hemiballism do to the indirect and direct pathways? What does it ultimately result in?

Answer 28

takes out the entire indirect pathway and lets the direct pathway dominate; results in increase in motor outputs

Question 29

When does Huntington's chorea usually express? What does it result in?

Answer 29

in the 4th and 5th decade; | results in movement disorder followed by dementia and death

Question 30

What symptoms of Huntington's disease are the first to manifest?

Answer 30

rapid, jerky dance-like movements in the extremities

Question 31

What is the initial insult in Huntington's disease? What does it ultimately lead to?

Answer 31

loss of striatal cells projecting to the indirect path **later complicated by a secondary loss of the small Ach cells of the striatum; increase in activity of motor thalamus

Question 32

When you consider Basal Ganglia disorders, it is useful to think about the hypo and hyperkinetic syndromes as being an imbalance between the (blank) and the (blank) in the striatum.

Answer 32

dopamine; ACh

Question 33

How can Parkinson's be treated?

Answer 33

increasing the level of dopamine

Question 34

How can Huntington's be "treated?"

Answer 34

elevate the ACh levels in the striatum

Question 35

What are other solutions to disorders of the basal ganglia?

Answer 35

give L-dopa as a precursor to dopamine transplant dopamine producing cells give stem cells deep brain stimulation

Question 36

What do lower motor neuron syndromes cause? What kind of deficit do they produce in the spinal cord?

Answer 36

paralysis muscle atrophy areflexia and atonia; ipsilateral deficit

Question 37

What do upper motor neuron syndromes cause? | What kind of deficit do they produce in the spinal cord?

Answer 37

paresis (weakness) no atrophy hyperflexia, hypertonia, spasticity contralateral deficit above the decussation and ipsilateral deficit below the decussation

Question 38

Do basal ganglia disorders cause paralysis? Atrophy? What kind of deficit do they produce in the spinal cord?

Answer 38

no; no; contralateral

Question 39

What is the effect of Parkinsons disease on the direct pathway?

Answer 39

Decreases the direct pathway!! Loss of the dopamine projecting cells from the nigra to the striatum. The loss on the direct path is to reduce excitation of the striatum which causes a decrease in motor activity. Essentially the small ACh cells become dominant.