The Motor System Overview

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Questions and Answers

Which nuclei are part of the basal ganglia?

Caudate, putamen, globus pallidus, subthalamic nucleus, substantia nigra (correct)

Cerebellum, thalamus, inferior colliculus, vestibular nuclei

Midbrain, cortex, red nucleus, substantia gelatinosum

Hippocampus, amygdala, basal forebrain, dorsomedial nucleus

What effect does the direct pathway of the basal ganglia have on motor activity?

It has no significant effect on motor activity.

It increases the overall muscle tone which affects all movements.

It facilitates movement by reducing inhibition on motor activity. (correct)

It suppresses motor function by enhancing inhibitory signals.

What is a common symptom of Parkinson's disease?

Excessive movement

Sudden bursts of activity

Tremors and stiffness (correct)

Overactivity in the cerebellum

What is the primary function of the basal ganglia compared to the cerebellum?

Basal ganglia control movement initiation and pattern selection, while cerebellum refines and coordinates ongoing movement. Signup and view all the answers

What type of disorder can result from lesions in the basal ganglia?

Both hyperkinetic (excessive movement) and hypokinetic (reduced movement) disorders Signup and view all the answers

What role does the Upper Motor Neuron (UMN) play in the motor system?

It initiates movement from the brain cortex. Signup and view all the answers

Which pathway in the motor system is primarily responsible for controlling fine, voluntary movements?

Lateral Pathways Signup and view all the answers

What is the main consequence of damage to Lower Motor Neurons (LMN)?

Flaccid paralysis Signup and view all the answers

How does the motor system utilize negative feedback?

By comparing intended and actual movements. Signup and view all the answers

What is a characteristic of spasticity resulting from Upper Motor Neuron lesions?

Increased muscle tone Signup and view all the answers

Which current understanding reflects the role of the cerebellum in movement?

It adjusts muscle actions based on sensory feedback. Signup and view all the answers

What is the role of the basal ganglia in the motor control loop?

To modulate and refine movement before it reaches the cortex. Signup and view all the answers

In the context of motor disorders, what do extrapyramidal disorders typically resemble?

Side effects of prescribed psychiatric medications. Signup and view all the answers

Which deep cerebellar nuclei are collectively referred to as the interpositus nucleus?

Globose and emboliform nuclei Signup and view all the answers

What type of input do climbing fibers provide to Purkinje cells?

Strong excitatory input Signup and view all the answers

Which area of the cerebellum is primarily responsible for trunk control?

Midline zone Signup and view all the answers

What is the main function of the deep cerebellar nuclei (DCN)?

Modulate motor control and coordination Signup and view all the answers

Which symptom is typically associated with dysfunction of the cerebellum?

Ataxia Signup and view all the answers

What role does the cerebellum play in motor learning?

It allows for the acquisition and refinement of new motor skills Signup and view all the answers

How do lesions in the cerebellum affect movement?

They cause action tremors and abnormal movement paths Signup and view all the answers

What happens to the posture of a person with cerebellar dysfunction?

The face turns contralaterally and ipsilateral shoulder is lowered Signup and view all the answers

Study Notes

The Motor System

The motor system allows for voluntary, complex movements.
Extrapyramidal disorders are common in people taking psychiatric medications.
Information flows across multiple control centers, using negative and feed-forward mechanisms.
Negative feedback adjusts movements by comparing intended and actual movements.
Feed-forward utilizes memory to anticipate and adjust for rapid movements.

How the Motor System Works

Motivation for movement originates in subcortical areas (limbic areas, hypothalamus, cerebellum, basal ganglia).
Motor programs (intended movement sequences) are developed in premotor and supplementary motor areas and relayed to the primary motor cortex.
Motor commands travel along two main pathways:
- Upper Motor Neuron (UMN): Initiates movement from the brain cortex.
- Lower Motor Neuron (LMN): Connects to muscles, enabling movement.
UMN lesions cause spasticity, exaggerated reflexes, and a positive Babinski sign.
LMN lesions result in flaccid paralysis, muscle atrophy, and loss of reflexes.

Major Pathways of Axons from the Brain

A loop, or pathway, involving the cerebral cortex, basal ganglia, thalamus, and back to the cortex has components: one for direct facilitation and another indirect inhibition.
Output from the Globus Pallidus Internal (GPi) and Substantia Nigra pars reticulata (SNr) is inhibitory to the thalamus.
Lateral Pathways (Direct): Control fine, voluntary movements; direct pathway inherent / spontaneous GPi activity is ↓ by striatal activity, leading to disinhibition, and facilitating movements.

The Cerebellum

Located in the back of the brain.
Crucial for movement coordination by receiving sensory information and adjusting muscle actions.
Its 4 deep nuclei (dentate, globose, emboliform, and fastigial, or interpositus) are largely responsible for output.
Cerebellar organization has zones for control of midline, limbs, and digits.
Input to the cerebellum occurs via mossy and climbing fibers.
Mossy fibers originate from diverse sources (cortex, spinal cord, and brainstem) to stimulate granule cells, and have weak excitatory input to Purkinje cells.
Climbing fibers originate in the inferior olivary nucleus, and provide strong excitatory input to Purkinje cells, leading to complex neural spikes.
Purkinje cells output to deep cerebellar nuclei.

Deep Cerebellar Nuclei

Signal: Inhibitory GABAergic output.
Target: Various brain regions, including the thalamus, red nucleus, and vestibular nuclei.
Signal: Excitatory output for modulating motor control and coordination.
The cerebellum's role encompasses timing and coordination of movement, motor learning, and balance and posture maintenance. It acts as a fine-tuning mechanism for movement.

Basal Ganglia

Five interconnected subcortical nuclei (caudate, putamen, globus pallidus, subthalamic nucleus, and substantia nigra).
Crucial for initiating and regulating movement.
Extensive connections between basal ganglia and motor areas of the brain.
Primary input from the cerebral cortex, output via thalamus, back to the cortex.
Direct pathway in facilitates movement by reducing inhibition.
Indirect pathway suppresses unnecessary movement by increasing inhibition.
Disorders can result in hyperkinetic (excessive movement) or hypokinetic (reduced movement) symptoms.

Differences Between Basal Ganglia and Cerebellum

Basal Ganglia: Controls movement initiation and pattern selection
Cerebellum: Refines and coordinates ongoing movement
Basal ganglia involved in cognitive movement planning, while the cerebellum adjusts movements in real-time.
Key Point : Basal gangliia are involved in cognitive planning of movement and the cerebellum adjusts real-time movements.

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Description

Explore the intricate workings of the motor system, focusing on how voluntary movements are initiated and controlled. This quiz covers key concepts such as motor pathways, feedback mechanisms, and the impact of motor neuron lesions. Perfect for those studying neuroscience or related fields.