Internal Motor Systems: Basal Ganglia Flashcards
List the 4 functions of the Basal Ganglia
- Preparation/Planning of Movement
- Initiation of Movement (inhibit/facilitate)
- Regulate Stereotypic Movement (sequencing/overlearned skills)
- Learning of New Motor Tasks
List the 5 Nuclei of the Basal Ganglia
- Caudate
- Putament
- Globus pallidus (internus and externus)
- Substania nigra
- Subthalamic nucleus
Describe what makes up the Lentifrom nucleus
The putamen and the globus pallidus
While they are geographically close they have different functions
Describe what makes up the Striatum
The caudate and the putamen
While they are geographically different they are functionally the same (main input to basal ganglia)
Structures: Input into basal ganglia
Caudate and Putamen
Structure: Output from the basal ganglia
Globus Pallidus
Structure: Gray matter, clusters of cell bodies deep within the cortex
Basal Ganglia
Loop: Internal motor circuit, basic loop through basal ganglia with major motor component
Striato-pallido-thalamic loop
Structure: Modulates that amount and type of output sent to the globus pallidus and eventually to the cortex
Substantia nigra
Structure: It’s connection to the globus pallidus allows for the modualtion of output from the basal ganglia
Subthalamic Nucleus
Term: explosive movements seen if damage occurs to the subthalamic nucleus
Ballism
Loop:
- Facilitates movement
- Goes through internal segment of globus pallidus
Direct Motor Pathway
Loop:
- Inhibits movement
- goes to external segment of globus pallidus
Indirect Motor Pathway
Loop:
- VL of thalamus released from inhibition
- Increased excitation of PMA/M1
- Activity of PMA/M1 BOOSTED
- POSITIVE FEEDBACK loop
Direct Motor Pathway
Describe the Direct Motor Pathway
- 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
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
Indirect Motor Pathway
Describe the Indirect Motor Pathway
- 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
Describe the areas the basal ganglia projects to
- Prefrontal cortex (cognitive component)
- Frontal eye fields
- Sensorimotor areas: M1, SMA, PMC, S1
- Limbic areas
- Parietal lobe
List the 3 loops that play a major role in cognition and mood
Dorsolateral prefrontal
Lateral orbitofrontal
Anterior cingulate
Loop: “Executive functions,” organizing behavior responses, problem solving
Dosrolateral prefrontal circuit
Loop: Cause of cognitive deficits in those with PD
Dorsolateral Prefrontal Circuit
Loop: Mediating empathetic and socially appropriate responses
Lateral Orbitofrontal Circuit
Loop: Responsible for flat affect in those with PD
Lateral orbitofrontal circuit
Loop: Cause of OCD, schizophrenia
Lateral orbitofrontal circuit
Loop: Motivated behavior and procedural learning
Anterior Cingulate Circuit
Function of Dorsolateral Prefrontal Circuit
Executive functions: organizing behavior responses, problem solving
Function of Lateral Orbitofrontal Circuit
Mediating empathetic and socially appropriate responses
Function of Anterior Cingulate Circuit
Motivated behavior and Procedural learning
Describe the effect of increased inhibition of the thalamus by the basal ganglia
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
Term: poverty of movement
Hypokinesia
Condition: When the putamen cann’t be activated secondary to loss of dopamine input from the substantia nigra
Parkinson’s Disease
Condition: Damage to putamen or globus pallidus
Parkinsonism
Describe the effect of decreased inhibition of the thalamus by the basal ganglia
Increased excitation of motor cortex = hyperkinesia
Occurs due to loss of connection with subthalamic nuclei or striatal neurons (indirect pathways lost)
Structure: Produced dopamine
Substantia nigra
Describe the effect of domapine on the direct and indirect pathways
EXCITES the DIRECT pathway
INHIBITS the INDIRECT pathway
Describe how dopamine facilitate movement
via suppression of the internal globus pallidus output
Describe the effect of domapine in PD
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
Term: wild flailing movements
Ballism
Describe the physiology behind hyperkinesia due to a basal ganglia dysfunction
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
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
Huntington’s Disease
Condition: Neurological syndrome dominated by sustained mm contractions causing twisting and repetitive movements or abnormal posture
Dystonia
Describe the pathogenesis of dystonia
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
Focal Dystonia: uncontrolled blinking or closure of eyelids
Blepharospasm
Focal Dystonia: Neck mm contract, turning head to one side or pulling it forward/backward
Cervical dystonia
Focal Dystonia: Face and jaw mm contract causing grimaces or facial distortion
Oromandibular dystonia
Focal Dystonia: Affecting speech mm of the throat cuasing strained, forced, or breathy speech
Dysphonia
