Cerebellum Basalganglia Flashcards
What are the primary roles of the cerebellum and basal ganglia in movement control?
Flashcard 1: Overview of Cerebellum and Basal Ganglia
The cerebellum and basal ganglia are collections of nuclei that modify movement on a minute-to-minute basis. They receive input from the motor cortex and send feedback via the thalamus, forming motor loops. The cerebellum provides excitatory output to the motor cortex, while the basal ganglia provides inhibitory output. A balance between these two systems ensures smooth, coordinated movement.
What are the levels of the motor system hierarchy?
Flashcard 2: Motor System Hierarchy
1) Motor areas in the cerebral cortex
2) Brainstem
3) Spinal cord
4) Motor circuits responsible for rhythmic movements, reflexes, and voluntary movements
5) Cerebellum and Basal Ganglia, which modify and fine-tune motor commands
How do the cerebellum and basal ganglia influence motor control via the thalamus?
Flashcard 3: Thalamus and Motor Control
The cerebellum sends excitatory output to the motor cortex, while the basal ganglia send inhibitory output. This interaction ensures balanced motor function. Disruptions in either system can lead to movement disorders.
What is the function of the basal ganglia (BG)?
Flashcard 4: Basal Ganglia Overview
The BG modulates the upper motor system by selecting and initiating actions. It does not have direct connections to the lower motor system; instead, it exerts its influence through upper motor neurons.
What are the main nuclei of the basal ganglia?
Flashcard 5: Basal Ganglia Structures
Caudate Nucleus
Putamen
Globus Pallidus (internal and external segments)
Subthalamic Nucleus (StN)
Substantia Nigra (SN) (pars compacta & pars reticulata)
Describe the input-output flow of the basal ganglia.
Flashcard 6: Basal Ganglia Input and Output
Inputs come from most cortical areas and the substantia nigra pars compacta.
The putamen and caudate (striatum) receive input and project to the globus pallidus and substantia nigra pars reticulata.
Outputs are sent to the upper motor system via the thalamus.
What is the general principle of basal ganglia function?
Flashcard 7: Basal Ganglia Function
The BG normally inhibits upper motor system activity.
It selects particular actions by releasing specific parts of the upper motor system from inhibition (disinhibition).
This mechanism allows voluntary movements to be initiated.
How do the direct and indirect pathways of the basal ganglia affect motor output?
Flashcard 8: Direct and Indirect Pathways
Direct Pathway: Increases activation of the motor cortex, facilitating movement.
Indirect Pathway: Decreases activation of the motor cortex, inhibiting movement.
Balance between these pathways ensures proper movement control.
What is the role of dopamine in basal ganglia function?
Flashcard 9: Dopamine and the Basal Ganglia
Dopaminergic input from the substantia nigra pars compacta modulates BG activity.
Increased dopamine decreases inhibition on the upper motor system, facilitating action and motivation.
How does Parkinson’s disease affect the basal ganglia?
Flashcard 10: Parkinson’s Disease
Loss of dopamine-producing neurons in the substantia nigra pars compacta.
Increased inhibition of the motor cortex, leading to difficulty in initiating movement (bradykinesia, rigidity, tremors).
How does Huntington’s disease affect the basal ganglia?
Flashcard 11: Huntington’s Disease
Degeneration of basal ganglia neurons leads to decreased inhibition of the motor system.
Results in hyperkinetic symptoms (excessive, uncontrolled movements, spasms).
What are the primary functions of the cerebellum?
Cerebellum Overview
Modulates the upper motor system but does not connect directly to the lower motor system.
Fundamental role in motor error reduction and learning.
Compares planned movements with actual movement and corrects errors.
What are the three subdivisions of the cerebellum, and their functions?
Flashcard 13: Cerebellum Subdivisions
Cerebrocerebellum: Involved in planning and execution of skilled movements.
Vestibulocerebellum: Regulates posture and eye movements.
Spinocerebellum: Controls body and limb movements, based on spinal input.
What are the key cell types in the cerebellum?
Flashcard 14: Neurons and Circuits of the Cerebellum
Granule Cells: Send parallel fibers to Purkinje cells.
Purkinje Cells: Integrate inhibitory and excitatory signals; main output of the cerebellar cortex.
Deep Nuclei: Final output of the cerebellum, sending excitatory signals to the thalamus and brainstem.
How does the cerebellum contribute to motor error correction?
Flashcard 15: Motor Error Correction
It acts as a comparator by comparing intended movement (from the motor cortex) with actual sensory feedback.
Computes an error signal and sends it to the upper motor system for correction.
This process allows for smooth, accurate movements.
How does the cerebellum regulate the Vestibulo-Ocular Reflex (VOR)?
Flashcard 16: Vestibulo-Ocular Reflex (VOR)
The VOR stabilizes vision by coordinating eye and head movements.
The cerebellum adjusts and fine-tunes this reflex for precision.
Damage to the cerebellum disrupts this learning process, impairing adaptation of the reflex.
