Motor System Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which area of the motor cortex is primarily responsible for the planning of complex voluntary movements?

Primary motor cortex

Supplementary motor area

Premotor area (correct)

Basal ganglia

What is the role of the cerebellum in motor control?

Sequencing motor activities and making adjustments (correct)

Planning all motor movements

Generating reflexive responses

Sending signals to the spinal cord only

Which statement about the primary motor cortex (PMC) is accurate?

It is located in the postcentral gyrus.

It stimulates movements bilaterally.

It causes coordinated movements rather than specific muscle contractions.

It is organized topographically according to body part function. (correct)

Which of the following best describes the types of motor output distinctions?

Reflexive and voluntary Signup and view all the answers

What characterizes the extrapyramidal system of motor pathways?

It is involved in indirect motor functions outside of pyramidal control. Signup and view all the answers

How does the motor cortex contribute to the adjustment of body posture?

By continuously adjusting movements even during actions Signup and view all the answers

Which functional aspect is NOT served by the convergence of inputs onto motor neurons?

Initiation of reflex actions Signup and view all the answers

Which of the following statements is true about the representation in the primary motor cortex?

The representation of body parts is upside down. Signup and view all the answers

Which part of the nervous system is primarily responsible for controlling precise, skillful movements?

Pyramidal system Signup and view all the answers

What is the primary effect of the extrapyramidal system on movements?

Providing background for skilled movements Signup and view all the answers

Which of the following structures primarily initiates the planning of movement?

Basal ganglia Signup and view all the answers

What type of paralysis is associated with a lower motor neuron lesion?

Flaccid paralysis Signup and view all the answers

Which descending pathway is mainly responsible for setting postural background for movements?

Rubrospinal tract Signup and view all the answers

What is one characteristic feature of upper motor neuron lesions?

Clonus Signup and view all the answers

How do upper and lower motor neurons differ in terms of their location?

Upper motor neurons reside in the cortex of the brain, lower motor neurons in the spinal cord and brainstem Signup and view all the answers

Which of the following is not a characteristic of an upper motor neuron lesion?

Fasiculation Signup and view all the answers

Study Notes

Motor System Objectives

Students should understand how skilled movements are planned and executed.
Students should be able to identify the motor cortex.
Students must describe pyramidal and extrapyramidal motor tracts.
Students need to discuss the cerebellum and basal ganglia functions.

Motor Cortex Subareas

The motor cortex is divided into three subareas: primary motor cortex, premotor area, and supplementary motor area.
The primary motor cortex controls specific muscle movements.
The premotor area is involved in planning and coordinating movements.
The supplementary motor area is responsible for complex and sequential movements.

Primary Motor Area (PMC)

Located within the precentral gyrus.
Topographically organized: the representation is proportional to the movement complexity of body parts. (e.g. hands, face and fingers are larger).
Representation is upside-down.
Innervates opposite side of the body, with some bilateral representation for the upper face.
Stimulation of a specific part generates specific muscle contractions, without coordinated movement.

Control of Movement

Inputs to motor neurons have three functions: initiating voluntary activity; adjusting posture for stable movement; and coordinating muscle action for smooth, precise movements.
Posture adjustment occurs continually, even during movement, and is coordinated by the cerebellum.

Motor Output Types

Two types of motor output exist: reflexive (involuntary) and voluntary.
Reflex responses, e.g. chewing, swallowing, scratching, walking, can be adjusted voluntarily.

Planning of Movement

Movement planning is a function of the cortex (association area), basal ganglia, and cerebellum (lateral portions).
Basal ganglia and cerebellum relay information to the premotor and motor cortex.
The cerebellum sequences motor activities and makes corrective adjustments during execution.

Motor Function

Two parallel systems of descending pathways originate in the cerebral cortex (upper motor neurons): the pyramidal (corticobulbar and corticospinal) and extrapyramidal systems.
Pyramidal tracts terminate in the brainstem (corticobulbar) or spinal cord (corticospinal) and control voluntary movements.
Extrapyramidal tracts govern motor functions beyond the pyramidal system, for postural control, gross movements, and muscle tone.

Descending Spinal Pathways - Pyramidal System

The pyramidal system mainly controls precise movements.
At the medulla, 80% of corticospinal fibres cross over, innervating distal muscles.
Remaining 20% innervate proximal muscles, directly synapsing with lower motor neurons.

Descending Spinal Pathways - Extrapyramidal System

Includes rubrospinal, reticulospinal, tectospinal, and vestibulospinal tracts.
Basal ganglia and thalamus influence these descending tracts.
The extrapyramidal system establishes the postural background for skilled movements, controlling gross subconscious movements and muscle tone.

Summary of Control of Movement

Movement Planning: basal ganglia, cerebellum, and cortical areas (association area).
Movement Execution: pyramidal tract controls precise skilled movements, while the extrapyramidal tract provides the necessary background for skilled movements and subconscious gross motor actions (e.g. walking).
Coordination: primarily performed by the cerebellum.

Upper and Lower Motor Neurons

Upper Motor Neurons: cell bodies in the cortex of the brain; synapse with lower motor neurons.
Lower Motor Neurons: cell bodies in the gray matter of the spinal cord and brainstem; synapse with muscles; also divided into alpha and gamma types.

Lesion Effects

Lower Motor Neuron Lesion: lesion at the anterior horn cells (or below); results in flaccid paralysis, hypotonicity, hyporeflexia, areflexia, fasciculation, and muscle atrophy.
Upper Motor Neuron Lesion: lesion above the anterior horn cells; results in spastic paralysis, hypertonicity, hyperreflexia, clonus, and a positive Babinski sign.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz explores the key concepts of the motor system, including the planning and execution of skilled movements, and the various functions of the motor cortex. Students will learn about the different subareas of the motor cortex, such as the primary motor cortex, premotor area, and supplementary motor area, as well as the roles of the cerebellum and basal ganglia. Test your understanding of these essential components and their interconnections!