Motor System Overview
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Motor System Overview

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Questions and Answers

What is the primary role of motor units in the motor system?

  • To integrate sensory information
  • To facilitate muscle contraction (correct)
  • To initiate reflex actions
  • To coordinate voluntary movements

    • Which level of the motor system is responsible for integrating peripheral information?

  • Cerebral cortex
  • Spinal cord
  • Thalamus
  • Integrative component (correct)

    • What aspect of movement and posture do spinal reflexes primarily depend on?

  • Sensory receptors in the muscles
  • Coordination within the spinal cord (correct)
  • Higher brain functions
  • Posture systems from the brainstem

    • Which system in the encephalic trunk primarily controls posture?

    <p>Medial system</p> Signup and view all the answers

    How do motor systems achieve high-speed and accurate movements?

    <p>Through a combination of reflexes and sensory information</p> Signup and view all the answers

    What defines the hierarchical organization of the motor system?

    <p>The arrangement of brain regions responsible for motor control</p> Signup and view all the answers

    Which component is essential for executing a motor command?

    <p>Sensory information</p> Signup and view all the answers

    Which structures are part of the integration component of the motor system?

    <p>Cerebral cortex and thalamus</p> Signup and view all the answers

    What role do higher nervous centers play in reflex movements?

    <p>They modulate reflex movements.</p> Signup and view all the answers

    Which phase is NOT part of the voluntary movement process?

    <p>Feedback Monitoring</p> Signup and view all the answers

    What type of information primarily triggers reflex movements?

    <p>Sensory information.</p> Signup and view all the answers

    Which part of the brain is crucial for the programming phase of voluntary movements?

    <p>Premotor cortex</p> Signup and view all the answers

    How does the execution of movement relate to proprioceptors?

    <p>Proprioceptors monitor signals during execution.</p> Signup and view all the answers

    What is the primary function of gamma motorneurons in relation to muscle spindles?

    <p>To keep the central part of the spindle elongated</p> Signup and view all the answers

    What initiates the relaxation of a muscle during the inverse myotatic reflex?

    <p>Increase of muscle tension</p> Signup and view all the answers

    What is the main purpose of the flexor reflex?

    <p>To facilitate limb flexion in response to pain</p> Signup and view all the answers

    How do Golgi tendon organs react to increased muscle tension?

    <p>They excite interneurons that activate antagonistic muscle neurons</p> Signup and view all the answers

    Which reflex is characterized by maintaining balance and posture during lower limb flexor reflexes?

    <p>Cruciate extensor reflex</p> Signup and view all the answers

    What is the primary result of activating a motor neuron innervating the quadriceps muscle?

    <p>Extension of the leg</p> Signup and view all the answers

    What initiates the patellar reflex?

    <p>Percussion of the patellar tendon</p> Signup and view all the answers

    Which type of reflex occurs after a quick stretch of the muscle?

    <p>Phasic stretch reflex</p> Signup and view all the answers

    What happens to the flexor muscles during the patellar reflex?

    <p>They are released and inhibited</p> Signup and view all the answers

    What is the role of the g motor neurons in tonic myotatic reflexes?

    <p>To maintain muscular tone</p> Signup and view all the answers

    What effect does the shortening of the muscle have on the muscle spindle?

    <p>Decreases the information sent to the spinal cord</p> Signup and view all the answers

    In what way do afferent fibers affect flexor muscles during a reflex?

    <p>They inhibit the flexor motor neurons</p> Signup and view all the answers

    What is a characteristic feature of tonic myotatic reflexes?

    <p>The muscle remains contracted as long as the spindle is active</p> Signup and view all the answers

    What is the role of the primary motor cortex, premotor cortex, and supplementary motor area?

    <p>They are involved in the planning of movement.</p> Signup and view all the answers

    Which type of reflex involves only one synapse?

    <p>Mono-synaptic reflex</p> Signup and view all the answers

    What is the function of sensory receptors in the reflex arc?

    <p>To transmit information to the central nervous system.</p> Signup and view all the answers

    What is a characteristic of the muscle spindle?

    <p>It consists of intrafusal muscle fibers.</p> Signup and view all the answers

    Which part of the reflex arc is responsible for commanding muscles to contract?

    <p>Efferent motor fibers</p> Signup and view all the answers

    What occurs when a muscle is stretched according to the information provided?

    <p>The spindles are stretched.</p> Signup and view all the answers

    Multi-synaptic reflexes include which of the following components?

    <p>One or more interneurons</p> Signup and view all the answers

    What initiates the transmission of action potentials in the muscle spindle?

    <p>Stretching of the muscle spindle</p> Signup and view all the answers

    Study Notes

    Motor System Overview

    • Motor systems facilitate reflexes and voluntary movements with precision and speed.
    • They integrate sensory input for effective motor command execution.
    • Communication occurs via receptors and afferent pathways for sensation, while motor units execute muscle contractions.

    Components of the Motor System

    • Sensory Component (Afferent System): Collects data from external and internal environments.
    • Integrative Component (Central): Processes peripheral sensory information and formulates responses.
    • Motor-Autonomic Component (Efferent System): Transmits commands to muscles (effectors).

    Hierarchical Organization

    • Three levels of motor system organization:
      • 1st Level: Cerebral cortex (motor areas).
      • 2nd Level: Thalamus, basal ganglia, cerebellum, and brainstem.
      • 3rd Level: Spinal cord coordinating muscle contractions and movements.

    Reflex Actions

    • Spinal Reflexes: Automatic responses coordinated in the spinal cord.
    • Voluntary Actions: Controlled by higher brain centers, distinguishable from reflex movements.

    Brainstem Systems

    • Contains the Medial System: Regulates posture.
    • Contains the Lateral System: Controls distal limb muscles and head movements.

    Cortical Motor Areas

    • Key regions include the primary motor cortex, premotor cortex, and supplementary motor area.
    • Essential for planning and executing movements; influence spinal reflexes.

    Reflex Circuitry

    • Reflex Arch: Basic neuronal circuit comprising:
      • Receptors > Afferent fibers > Integration center > Efferent motor fibers > Effectors (muscles).

    Types of Reflexes

    • Mono-synaptic: Simplest form with one sensory neuron directly interfacing with a motor neuron.
    • Multi-synaptic: Involves multiple interneurons facilitating greater complexity.

    Muscle Spindles

    • Proprioceptors that measure muscle length via intrafusal fibers.
    • Activated upon muscle stretching, transmitting action potentials to the spinal cord.

    Myotatic Reflex Example

    • Known as the Patellar Reflex:
      • Quadriceps contraction results from hammer stroke on patellar tendon.
      • Process includes activation of extensor muscles and inhibition of flexor muscles during reflex action.

    Reflex Variations

    • Phasic Reflexes: Brief contraction following a quick stretch.
    • Tonic Reflexes: Maintain muscle contraction during sustained stretch.

    Role of Gamma Motor Neurons

    • Maintain muscle spindle sensitivity during shortening, ensuring continued accurate stimulation.

    Golgi Tendon Organs

    • Located at muscle-tendon junctions, respond to muscle tension changes.
    • Trigger relaxation of the ipsilateral muscle and contraction of the antagonist muscle during high tension.

    Flexor Reflex

    • Multi-synaptic reflex activating flexors in reaction to nociceptive stimuli.
    • Often accompanied by a contralateral extensor reflex for balance.

    Reflex Modulation

    • Modulated by higher nervous centers (brainstem, motor cortex) and sensory feedback.

    Phases of Voluntary Movements

    • Programming: Managed by premotor and supplementary motor areas.
    • Initiation: Occurs in the primary motor cortex.
    • Execution: Continuously adjusted through feedback from proprioceptors, with integration from basal ganglia and cerebellum for smooth coordination.

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    Description

    This quiz covers the fundamental concepts of the motor system, including the roles of receptors, afferent pathways, and motor units in sensation and muscle contraction. It also explores how sensory information is integrated to produce coordinated motor commands.

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