Lecture 4 - Basal Ganglia

Question 1

What is the basal ganglia and where is it located?

Answer 1

-beneath the cerebral cortex and is a cluster of cell bodies within the CNS and is made up of interconnected structures

Question 2

What makes up the striatum of the basal ganglia?

Answer 2

the caudate nucleus and the putamen

Question 3

What is the striatum highly innervated by?

Answer 3

dopaminergic neurons from the substantia nigra (SNpc)

Question 4

What is the primary cell type in the caudate-putamen complex and what type of neuron are they?

Answer 4

Medium Spiny Neurons (MSNs) and they are GABAergic

Question 5

What is the globus pallidus and its two subsections?

Answer 5

-it makes up the pallidum and had the globus pallidus interna and the globus pallidus externa

Question 6

What is the GPi?

Answer 6

structure packed with inhibitory or GABAergic motor neurons that project to the motor thalamus

Question 7

What is the GPe?

Answer 7

structure packed with inhibitory GABAergic neurons that projects to the STN or the subthalamic nucleus

Question 8

What is the STN?

Answer 8

it is a nucleus packed with excitatory Glutamatergic neurons that project back to the GPi

Question 9

What is the substantia nigra, what does it do, what it is color?

Answer 9

-where dopamine production and synthesis in the brain occurs, has a dark color due to chemical byproducts of dopamine production, and has the dopaminergic neurons which project to the striatum

Question 10

What is the major cell type in the striatum (caudate-putamen complex) and the basal ganglia overall?

Answer 10

medium spiny neurons MSNs and they are GABAergic

Question 11

What dopamine receptors do MSNs in the striatum express?

Answer 11

D1 receptors and D2 receptors

Question 12

What are D1 receptors?

Answer 12

-they are receptors that bind dopamine and correspond to the direct pathway for signaling; are metabotropic receptors and they promote the activity of adenylate cyclase in the cell with the net result of signaling via these receptors being the initiation of movement

Question 13

What are D2 receptors on MSNs?

Answer 13

bind dopamine and they correspond to the indirect pathway for signaling they are also metabotropic meaning GPCR and they INHIBIT the activity of adenylate cyclase in the cell causing the net result of termination of movement

Question 14

What is the Direct pathway?

Answer 14

the cortex and and SNpc —excitatory (Glu +) and DA+—–striatum—-GABA- —-GPi——GABA- —–Thalamus —-Glu+—-Cortex

initiate movement

Question 15

What is the indirect pathway?

Answer 15

Cortex and SNpc ——Glu_, DA- ——-Striatum—–GABA- ——-GPe—–GABA - ——–STN—Glu+——–GPi——GABA- ——-Thalamus —–Glu+——-Cortex

terminate movement

Question 16

What is a hypokinetic disorder?

Answer 16

Parkinsons Disease

Question 17

What causes Parkinsons Disease?

Answer 17

decreased dopamine production in substantia nigra causing less DA signaling via the direct pathway

Question 18

What drug was used to treat Parkinsons Disease?

Answer 18

L-Dopa but they began to show hyperkinesis

Question 19

What are other new methods of treatment to promote dopamine synthesis in the SNpc for PD?

Answer 19

deep brain stimulation

Question 20

What are two hyperkinetic disorders?

Answer 20

Huntington’s Disease and Hemiballism

Question 21

What is Huntington’s Disease?

Answer 21

-autosomal dominant genetic disorder that comes from the expansion of the CAG trinucleotide repeat which causes uncontrollable movements meaning deterioration of the inhibitory D2 pathway sue to loss of MSNs in the D2 pathway

Question 22

What is hemiballism?

Answer 22

result of a unilateral brain injury or stroke which affects the STN causing uncontroallable body movements on one side since the STN is doing less excitatory signaling causing less inhibition by the GPi of the thalamus causing the thalamus to not lees excite but actually still excite the motor cortex

Question 23

What part of the basal ganglia is implicated in non motor functions?

Answer 23

ventral side

Question 24

What are the three major non motor functions the basal ganglia is involved in?

Answer 24

decision making and executive functioning, reward learning, motivation

Question 25

How does the basal ganglia modulate decision making?

Answer 25

during adolescence when the connections between the frontal and limbic corticies begin to take shape and become more refined

Question 26

How does the basal ganglia modulate reward learning?

Answer 26

-one of the most important limbic functions which is via signaling in the ventral aspects of the basal ganglia which is the nucleus accumbens and the ventral tegmental area, thought to play a role in addicition

Question 27

How does the basal ganglia modulate motivation?

Answer 27

this is due to the fact that the basal ganglia is the dopamine hub of the brain or CNS