Basal Ganglia

Question 1

Dysdiadochokinesia is ______________.

Answer 1

disorder of rapidly alternating movement

Question 2

The basal ganglia is derived from ______________.

Answer 2

the ganglionic eminence –a group that becomes GABAergic

Question 3

Contrast the roles of the basal ganglia and cerebellum in movement.

Answer 3

The cerebellum coordinates movement from sensory inputs, while the basal ganglia mediates the frontal, executive functions of movement.

Question 4

The most caudal portions of the telencephalon have __________ levels of SHH.

Answer 4

low

Question 5

Again, what is the nucleus accumbens?

Answer 5

The point where the caudate and putamen come together

Question 6

Describe the direct pathway in the cortex, striatum, globus pallidus, and thalamus.

Answer 6

The putamen, in response to stimulation of D1 receptors, releases GABA onto the internal globus pallidus. The globus pallidus, which had been inhibiting the thalamus, is stopped and the thalamus then facilitates cortical function.

Question 7

The globus pallidus externa provides tonic inhibition to the __________.

Answer 7

subthalamic nuclei (this is the indirect pathway)

Question 8

Describe the indirect pathway.

Answer 8

D2 neurons in the caudate inhibit the globus pallidus externa. The globus pallidus externa then stops inhibiting the subthalamic nuclei. The subthalamic nucleus excites the globus pallidus interna, which then inhibits the thalamus. Thus, the thalamus is prevented from exciting the cortex.

Question 9

In the presence of dopamine, the balance is tilted toward the ______________. That is why Parkinson’s results in hypokinesia.

Answer 9

direct (facilitatory) pathway, because D1 is an excitatory receptor

Question 10

The basal ganglia receive no _________ input and send out no _________.

Answer 10

direct sensory; direct motor output

Question 11

True or false: unilateral basal ganglia lesions produce bilateral defects.

Answer 11

False. The basal ganglia coordinate with only the ipsilateral side of the cerebrum and thus produce contralateral deficits.

Question 12

The substantia nigra receives a projection from the ___________.

Answer 12

striatum (this is in addition to its projection that it sends back to the striatum –the dopamine-releasing neurons)

Question 13

The substantia nigra also projects to the ________.

Answer 13

thalamus

Question 14

True or false: both D1 and D2 receptors are stimulated by dopamine.

Answer 14

False. Dopamine inhibits D2 receptors.

Question 15

The putamen receives input mainly from the ___________.

Answer 15

sensory domains of the cortex

Question 16

The putamen projects onto the same cells as axons from what other structure?

Answer 16

The dentate nuclei of the cerebellum. They both synapse on the VA/VL nuclei of the thalamus.

Question 17

Which part of the cortex connects to the caudate?

Answer 17

The frontal lobes (it is thought that this connection underlies the link between cognitive disorders and movement disorders)

Question 18

The olfactory areas of the brain connect to which part of the basal ganglia?

Answer 18

The nucleus accumbens

Question 19

One key to understanding the workings of the basal ganglia system is that pallidal cells have an intrinsic ___________.

Answer 19

firing rate

Question 20

What is known to increase the tremor of Parkinson’s?

Answer 20

Emotional stress

Question 21

Parkinson’s patients walk without ___________.

Answer 21

any extraneous movements

Question 22

The symptoms of Huntington’s can be mimicked by administering _______________.

Answer 22

excess dopamine

Question 23

Describe the pathophysiology of hemiballismus.

Answer 23

A stroke in the PCA near the subthalamic nucleus can lead to loss of subthalamic output on the internal globus pallidus. The loss of GPI stimulation leads to increased movement.

Question 24

Decreases in the indirect pathway lead to what kind of disorders?

Answer 24

Hyperkinetic (because the inhibitory pathway is down)

Question 25

Decreases in the direct pathway lead to ____________.

Answer 25

hypokinetic disorders