Lecture 40 - Basal Ganglia

Question 1

What are the 3 functions of the basal ganglia

Answer 1

Provides dual function in regulating movements:
1) Allows desired movement to occur
2) Inhibits competing non-intended movements

Separate:
3) Emotional, motivational and cognitive functioning

Question 2

*The basal ganglia consists of what 5 parts (which parts are found in the striatum and the corpus striatum)

Answer 2

Question 3

describe the motor loops of input and output of the basal ganglia

Answer 3

1)Cortical input -> Striatum
2) output: Globus Pallidus (interna) -> thalamus

Question 4

What 2 neurotransmitters are involved in the 2 motor loops (excitatory or inhibitory)

Answer 4

1) GABA - inhibitory
2) Glutamate - Excitatory

Question 5

What are the 2 key pathways of movement in the basal ganglia and their function

Answer 5

1) Direct Pathway -> Allows desired movement to occur
2) Indirect Pathway-> Ihibits competing non-intended movements

Question 6

Cells of the substantia nigra produce what neurotransmitter

Answer 6

Dopamine

Question 7

Nigrostriatal projections (substantia nigra) influence

Answer 7

direct and indirect pathways of the striatum

Question 8

Describe substantia nigra’s effect on the direct loop and indirect loop of the striatum

Answer 8

Direct Loop -> dopamine acts on D1 receptors (excitatory) which facilitates the direct loop (desired movements) of the striatum (basal ganglia)
Indirect Loop-> dopamine acts on D2 receptors (inhibitory) which inhibits the indirect loop (competing movements)

Question 9

what is the role of thalamus in motor control also what animal is thalamus?

Answer 9

Modulates how the brain talks to the muscle (always excitatory)
thalamus = Oakley

Question 10

How does the globus pallidus modulate the thalamus

Answer 10

The globus pallidus acts like a leash on the thalamus:
Tight leash = Controls the thalamus and maintains movement inhibition so no movement occurs
Loose Leash = Decreases inhibition on thalamus causing lots of activity resulting in movement

Question 11

direct pathway in the basal ganglia causes the leash to ________ vs. indirect pathway _______ the leash

Answer 11

1. loosen
2. tightens

Question 12

What area of the brain sends input to the BG and what area modulates motor movements?

Answer 12

1. cortex - prefrontal, frontal and parietal
2. Area 6

Question 13

What 4 things does BG have a role in modulating?

Answer 13

1. motor
2. oculomotor
3. cognitive/executive (dorsolateral prefrontal cortex)
4. Emotional/social (lateral orbitofrontal cortex)

Question 14

Describe the direct pathway

Answer 14

The direct loop disinhibits (excites) thalamocortical projections

Question 15

Describe the indirect loop pathway

Answer 15

Indirect loop inhibits thalamocortical projections because the subthalamic nucleus increases the outflow of the globus pallidus internal resulting in inhibition of the thalamus

Question 16

List 3 negative signs (initiation is challenging/less activity) of basal ganglia disorders

Answer 16

1. Akinesia (no movement)
2. Bradykinesia (slow movement)
3. Abnormal postural adjustments

Question 17

List 2 positive signs (unintended movements) of basal ganglia disorders

Answer 17

1. Alterations in muscle tone (hypertonicity)
2. Dyskinesia (tremors, chorea, athetosis, ballismus, tics)

Question 18

Imbalance in direct and indirect pathways of basal ganglia disorders (negative and positive signs) result in

Answer 18

Increased fall risk

Question 19

Describe Parkinson’s disease in terms of how it occurs, some clinical presentations, and treatment options

Answer 19

Clinical Presentations:
-Paralysis agitans
-Tremor (pill-rolling movement)
-Rigidity
-Akinesia
-Bradykinesia
-Abnormal postural adjustments
-Mask-like facial expression
-Stooped posture

How it occurs: Degeneration of dopaminergic neurons in substantia nigra

Treatment:
-L-Dopa
-Surgery (Ablation of internal pallidum)

Question 20

T or F: BG is involved in only motor movements

Answer 20

false, BG works on motor movements and social/emotional