Basal Ganglia Pathways
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Questions and Answers

What is the origin of the motor loop through the basal ganglia?

  • Direct connections from the thalamus
  • Inhibitory connections from the cortex
  • Inhibitory connections from the thalamus
  • Excitatory connections from the cortex (correct)

    • What is the role of the direct pathway through the basal ganglia?

  • Enhance the initiation of desired movements (correct)
  • Facilitate sensory processing
  • Suppress cortical activation
  • Inhibit the initiation of movements

    • What effect does cortical activation have on putamen neurons?

  • Excites putamen neurons (correct)
  • Inhibits putamen neurons
  • Causes degeneration of putamen neurons
  • No effect on putamen neurons

    • What is the role of neurons in the internal segment of the globus pallidus at rest?

    <p>Tonic inhibition of VL</p> Signup and view all the answers

    What happens when putamen neurons inhibit GPi neurons?

    <p>Release VLo cells from inhibition</p> Signup and view all the answers

    What is the effect of VLo activity on the SMA?

    <p>Boosts the activity of the SMA</p> Signup and view all the answers

    What is the function of the circuit involving VLo and SMA?

    <p>Acts as a positive-feedback loop to focus cortical activation onto the SMA</p> Signup and view all the answers

    What tends to antagonize the motor functions of the direct pathway?

    <p>The complex indirect pathway through the basal ganglia</p> Signup and view all the answers

    Which nucleus is excited by axons from the cortex and its projections excite the neurons of the GPi?

    <p>Subthalamic nucleus</p> Signup and view all the answers

    What does the activation of the indirect pathway by the cortex tend to do to the thalamus?

    <p>Inhibit</p> Signup and view all the answers

    What is the role of the direct pathway in selecting motor actions?

    <p>Facilitates certain motor actions</p> Signup and view all the answers

    Which structure is inhibited by cells of the GPe and then inhibits cells of both the GPi and subthalamic nucleus?

    <p>GPi</p> Signup and view all the answers

    What is the role of the indirect pathway in relation to competing motor programs?

    <p>Suppresses competing motor programs</p> Signup and view all the answers

    Which pathway tends to facilitate the thalamus and information passing through it?

    <p>Direct pathway</p> Signup and view all the answers

    What is the most unique feature of the indirect pathway?

    <p>GPe and subthalamic nucleus</p> Signup and view all the answers

    What tends to antagonize the motor functions of the direct pathway?

    <p>The complex indirect pathway through the basal ganglia</p> Signup and view all the answers

    Which nucleus is excited by axons from the cortex and its projections excite the neurons of the GPi?

    <p>Subthalamic nucleus</p> Signup and view all the answers

    What tends to inhibit the thalamus when activated by the cortex?

    <p>The indirect pathway</p> Signup and view all the answers

    Which pathway may help to select certain motor actions?

    <p>The direct pathway</p> Signup and view all the answers

    What is inhibited by cells of the GPe, which then inhibit cells of both the GPi and subthalamic nucleus?

    <p>GPi</p> Signup and view all the answers

    Which neurons does the subthalamic nucleus excite?

    <p>GPi neurons</p> Signup and view all the answers

    What does the activation of the direct pathway by the cortex tend to facilitate?

    <p>Thalamus</p> Signup and view all the answers

    What does the indirect pathway simultaneously suppress?

    <p>Competing and inappropriate motor programs</p> Signup and view all the answers

    What is the origin of the motor loop through the basal ganglia?

    <p>Excitatory connections from the cortex</p> Signup and view all the answers

    In the direct pathway through the basal ganglia, synapses from cortical cells excite cells in the ________.

    <p>Putamen</p> Signup and view all the answers

    What is the role of the direct pathway through the basal ganglia?

    <p>Enhance the initiation of desired movements</p> Signup and view all the answers

    What is the effect of cortical activation on putamen neurons?

    <p>Excitation</p> Signup and view all the answers

    Neurons in the internal segment of the globus pallidus tonically inhibit which structure?

    <p>Ventrolateral nucleus (VLo)</p> Signup and view all the answers

    What is the role of the internal segment of the globus pallidus in the motor loop?

    <p>Spontaneously active at rest</p> Signup and view all the answers

    What is the function of the positive-feedback loop in the circuit?

    <p>Focus the activation of widespread cortical areas onto the supplementary motor area</p> Signup and view all the answers

    Study Notes

    Origin of the Motor Loop

    • The motor loop originates from the cerebral cortex, specifically areas involved in motor control.

    Role of the Direct Pathway

    • The direct pathway facilitates selected motor actions by providing excitatory inputs to the motor thalamus, increasing motor activity.

    Effect of Cortical Activation on Putamen Neurons

    • Cortical activation leads to excitation of putamen neurons, enhancing their activity in the motor loop.

    Neurons in the Internal Segment of the Globus Pallidus at Rest

    • These neurons tonically inhibit the thalamus, preventing unwanted motor activity when at rest.

    Inhibition of GPi Neurons by Putamen Neurons

    • When putamen neurons inhibit GPi neurons, it reduces inhibitory output to the thalamus, allowing increased movement.

    Effect of VLo Activity on the Supplementary Motor Area (SMA)

    • VLo activity enhances the excitability of the SMA, promoting motor planning and execution.

    Function of Circuit Involving VLo and SMA

    • This circuit plays a crucial role in coordinating and planning motor actions, linking higher-order cognitive functions with motor control.

    Antagonism of the Direct Pathway

    • The indirect pathway tends to antagonize motor functions of the direct pathway, competing for the same motor outputs.

    Nucleus Excited by Cortical Axons

    • The subthalamic nucleus is excited by cortical axons, which project to and excite GPi neurons, influencing movement.

    Activation of the Indirect Pathway by Cortex

    • Activation of the indirect pathway leads to increased inhibition of the thalamus, thereby reducing motor output.

    Role of Direct Pathway in Action Selection

    • It assists in the selection of desired motor actions, helping to streamline movement execution.

    Structure Inhibited by GPe

    • The Globus Pallidus externus (GPe) inhibits neurons in both the GPi and the subthalamic nucleus, modulating their activity.

    Role of Indirect Pathway for Competing Motor Programs

    • It functions to suppress competing motor programs that may interfere with the execution of desired movements.

    Pathway that Facilitates Thalamus

    • The direct pathway through the basal ganglia facilitates the thalamus, promoting informational flow relevant to movement.

    Unique Feature of the Indirect Pathway

    • The indirect pathway's unique feature is simultaneous suppression of unwanted motor activities while enhancing the inhibition of the thalamus.

    Antagonism of Direct Pathway by Other Functions

    • The indirect pathway's activity antagonizes the facilitation of motor functions provided by the direct pathway.

    Neurons Excited by Subthalamic Nucleus

    • The subthalamic nucleus excites neurons in the GPi, contributing to movement regulation.

    Direct Pathway Activation and Facilitation

    • Activation of the direct pathway by cortical signals tends to facilitate voluntary movements.

    Indirect Pathway Suppression

    • The indirect pathway simultaneously suppresses motor activities that are not selected for execution.

    Positive-Feedback Loop Function

    • The positive-feedback loop within the circuit enhances specific motor outputs and reinforces selected motor actions, contributing to efficient motor control.

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    Description

    Test your knowledge of the direct and indirect pathways through the basal ganglia with this quiz. Explore the motor loop originating from the cortex and the excitatory and inhibitory connections within the basal ganglia.

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