Internal Motor Systems: Basal Ganglia

Question 1

List the 4 functions of the Basal Ganglia

Answer 1

• Preparation/Planning of Movement
• Initiation of Movement (inhibit/facilitate)
• Regulate Stereotypic Movement (sequencing/overlearned skills)
• Learning of New Motor Tasks

Question 2

List the 5 Nuclei of the Basal Ganglia

Answer 2

1. Caudate
2. Putament
3. Globus pallidus (internus and externus)
4. Substania nigra
5. Subthalamic nucleus

Question 3

Describe what makes up the Lentifrom nucleus

Answer 3

The putamen and the globus pallidus

While they are geographically close they have different functions

Question 4

Describe what makes up the Striatum

Answer 4

The caudate and the putamen

While they are geographically different they are functionally the same (main input to basal ganglia)

Question 5

Structures: Input into basal ganglia

Answer 5

Caudate and Putamen

Question 6

Structure: Output from the basal ganglia

Answer 6

Globus Pallidus

Question 7

Structure: Gray matter, clusters of cell bodies deep within the cortex

Answer 7

Basal Ganglia

Question 8

Loop: Internal motor circuit, basic loop through basal ganglia with major motor component

Answer 8

Striato-pallido-thalamic loop

Question 9

Structure: Modulates that amount and type of output sent to the globus pallidus and eventually to the cortex

Answer 9

Substantia nigra

Question 10

Structure: It’s connection to the globus pallidus allows for the modualtion of output from the basal ganglia

Answer 10

Subthalamic Nucleus

Question 11

Term: explosive movements seen if damage occurs to the subthalamic nucleus

Answer 11

Ballism

Question 12

Loop:

• Facilitates movement
• Goes through internal segment of globus pallidus

Answer 12

Direct Motor Pathway

Question 13

Loop:

• Inhibits movement
• goes to external segment of globus pallidus

Answer 13

Indirect Motor Pathway

Question 14

Loop:

• VL of thalamus released from inhibition
• Increased excitation of PMA/M1
• Activity of PMA/M1 BOOSTED
• POSITIVE FEEDBACK loop

Answer 14

Direct Motor Pathway

Question 15

Describe the Direct Motor Pathway

Answer 15

• VL of thalamus released from inhibition
• Increased excitation of PMA/M1
• Activity of PMA/M1 BOOSTED
• POSITIVE FEEDBACK loop

Facilitates movement, via internal segment of globus pallidus

Question 16

Loop:

• Increased inhibition of VL of thalamus via loop b/t external globus pallidus and subthalamic nucleus
• Decreased excitation of PMA/M1
• Decreased activity of PMA/M1
• NEGATIVE FEEDBACK

Answer 16

Indirect Motor Pathway

Question 17

Describe the Indirect Motor Pathway

Answer 17

• Increased inhibition of VL of thalamus via loop b/t external globus pallidus and subthalamic nucleus
• Decreased excitation of PMA/M1
• Decreased activity of PMA/M1
• NEGATIVE FEEDBACK

Inhibits movement, via external segment of globus pallidus

Question 18

Describe the areas the basal ganglia projects to

Answer 18

• Prefrontal cortex (cognitive component)
• Frontal eye fields
• Sensorimotor areas: M1, SMA, PMC, S1
• Limbic areas
• Parietal lobe

Question 19

List the 3 loops that play a major role in cognition and mood

Answer 19

Dorsolateral prefrontal

Lateral orbitofrontal

Anterior cingulate

Question 20

Loop: “Executive functions,” organizing behavior responses, problem solving

Answer 20

Dosrolateral prefrontal circuit

Question 21

Loop: Cause of cognitive deficits in those with PD

Answer 21

Dorsolateral Prefrontal Circuit

Question 22

Loop: Mediating empathetic and socially appropriate responses

Answer 22

Lateral Orbitofrontal Circuit

Question 23

Loop: Responsible for flat affect in those with PD

Answer 23

Lateral orbitofrontal circuit

Question 24

Loop: Cause of OCD, schizophrenia

Answer 24

Lateral orbitofrontal circuit

Question 25

Loop: Motivated behavior and procedural learning

Answer 25

Anterior Cingulate Circuit

Question 26

Function of Dorsolateral Prefrontal Circuit

Answer 26

Executive functions: organizing behavior responses, problem solving

Question 27

Function of Lateral Orbitofrontal Circuit

Answer 27

Mediating empathetic and socially appropriate responses

Question 28

Function of Anterior Cingulate Circuit

Answer 28

Motivated behavior and Procedural learning

Question 29

Describe the effect of increased inhibition of the thalamus by the basal ganglia

Answer 29

Reduced excitatio of the motor cortex = hypokinesia This occurs when the putamen can't be activated due to loss of dopamine or damage to the putamen OR globus pallidus

Question 30

Term: poverty of movement

Answer 30

Hypokinesia

Question 31

Condition: When the putamen cann't be activated secondary to loss of dopamine input from the substantia nigra

Answer 31

Parkinson's Disease

Question 32

Condition: Damage to putamen or globus pallidus

Answer 32

Parkinsonism

Question 33

Describe the effect of decreased inhibition of the thalamus by the basal ganglia

Answer 33

Increased excitation of motor cortex = hyperkinesia Occurs due to loss of connection with subthalamic nuclei or striatal neurons (indirect pathways lost)

Question 34

Structure: Produced dopamine

Answer 34

Substantia nigra

Question 35

Describe the effect of domapine on the direct and indirect pathways

Answer 35

EXCITES the DIRECT pathway INHIBITS the INDIRECT pathway

Question 36

Describe how dopamine facilitate movement

Answer 36

via suppression of the internal globus pallidus output

Question 37

Describe the effect of domapine in PD

Answer 37

Loss of dopamine results in DECREASED activity in the DIRECT pathway and INCREASED activity in the INDIRECT pathway which ENHANCES output from the INTERNAL globus pallidus resulting in INCREASED INHIBITION of the thalamus and REDUCED excitation fo the motor cortex

Question 38

Term: wild flailing movements

Answer 38

Ballism

Question 39

Describe the physiology behind hyperkinesia due to a basal ganglia dysfunction

Answer 39

There is a loss of excitatory subthalamic nucleus connection to the internal globus pallidus which DISINHIBITS the VL of the thalamus resulting in INCREASED excitation of the PMA/M1

Question 40

Condition: - Hyperkinesia and cognitive impairments - Autosomal dominant - Onset from 30-50 yo; death w/in 15-20 yrs - Indirect pathway lost due to dysfunction in the striatum

Answer 40

Huntington's Disease

Question 41

Condition: Neurological syndrome dominated by sustained mm contractions causing twisting and repetitive movements or abnormal posture

Answer 41

Dystonia

Question 42

Describe the pathogenesis of dystonia

Answer 42

Dystonia occurs due to a defect in the descending pathways involving reciprocal inhibition of motor neurons which results in co-contraction of agonists and antagonists Dystonia can also be a result of chemcial dysfunction in the basal ganglia leading to poor inhibition of motor control

Question 43

Focal Dystonia: uncontrolled blinking or closure of eyelids

Answer 43

Blepharospasm

Question 44

Focal Dystonia: Neck mm contract, turning head to one side or pulling it forward/backward

Answer 44

Cervical dystonia

Question 45

Focal Dystonia: Face and jaw mm contract causing grimaces or facial distortion

Answer 45

Oromandibular dystonia

Question 46

Focal Dystonia: Affecting speech mm of the throat cuasing strained, forced, or breathy speech

Answer 46

Dysphonia