Lecture 40 - Basal Ganglia Flashcards
What are the 3 functions of the basal ganglia
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
*The basal ganglia consists of what 5 parts (which parts are found in the striatum and the corpus striatum)
describe the motor loops of input and output of the basal ganglia
1)Cortical input -> Striatum
2) output: Globus Pallidus (interna) -> thalamus
What 2 neurotransmitters are involved in the 2 motor loops (excitatory or inhibitory)
1) GABA - inhibitory
2) Glutamate - Excitatory
What are the 2 key pathways of movement in the basal ganglia and their function
1) Direct Pathway -> Allows desired movement to occur
2) Indirect Pathway-> Ihibits competing non-intended movements
Cells of the substantia nigra produce what neurotransmitter
Dopamine
Nigrostriatal projections (substantia nigra) influence
direct and indirect pathways of the striatum
Describe substantia nigra’s effect on the direct loop and indirect loop of the striatum
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)
what is the role of thalamus in motor control also what animal is thalamus?
Modulates how the brain talks to the muscle (always excitatory)
thalamus = Oakley
How does the globus pallidus modulate the thalamus
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
direct pathway in the basal ganglia causes the leash to ________ vs. indirect pathway _______ the leash
- loosen
- tightens
What area of the brain sends input to the BG and what area modulates motor movements?
- cortex - prefrontal, frontal and parietal
- Area 6
What 4 things does BG have a role in modulating?
- motor
- oculomotor
- cognitive/executive (dorsolateral prefrontal cortex)
- Emotional/social (lateral orbitofrontal cortex)
Describe the direct pathway
The direct loop disinhibits (excites) thalamocortical projections
Describe the indirect loop pathway
Indirect loop inhibits thalamocortical projections because the subthalamic nucleus increases the outflow of the globus pallidus internal resulting in inhibition of the thalamus
List 3 negative signs (initiation is challenging/less activity) of basal ganglia disorders
- Akinesia (no movement)
- Bradykinesia (slow movement)
- Abnormal postural adjustments
List 2 positive signs (unintended movements) of basal ganglia disorders
- Alterations in muscle tone (hypertonicity)
- Dyskinesia (tremors, chorea, athetosis, ballismus, tics)
Imbalance in direct and indirect pathways of basal ganglia disorders (negative and positive signs) result in
Increased fall risk
Describe Parkinson’s disease in terms of how it occurs, some clinical presentations, and treatment options
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)
T or F: BG is involved in only motor movements
false, BG works on motor movements and social/emotional
