Neurology: Upper and Lower Motor Neuron Disorders

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Questions and Answers

What occurs when an injury is above the level of decussation?

  • Paralysis on the same side of the body
  • No effect on motor function
  • Flaccid paralysis in lower motor neurons
  • Contralateral symptoms (correct)

What type of motor neuron disorder is characterized by the inability of muscles to relax?

  • Ataxic cerebral palsy
  • Spastic cerebral palsy (correct)
  • Chorea
  • Athetoid cerebral palsy

Which clinical manifestation is most closely associated with amyotrophic lateral sclerosis (ALS)?

  • Difficulty controlling balance and coordination
  • Regular involuntary muscle contractions
  • Tremor in whole muscle groups
  • Rapid progression leading to muscle weakness (correct)

Which of the following best describes Brown-Sequard syndrome?

<p>Loss of motor function on one side and pain/temp sensation on the other (A)</p> Signup and view all the answers

In what manner do lower motor neuron disorders differ from upper motor neuron disorders?

<p>Lower motor neuron lesions lead to flaccid paralysis (B)</p> Signup and view all the answers

What is the primary consequence of a complete spinal cord injury?

<p>Loss of sensation and motor function below the level of injury (C)</p> Signup and view all the answers

Which term describes the condition of excessive motor activity without purpose?

<p>Hyperkinesia (A)</p> Signup and view all the answers

What neurological disorder is characterized by involuntary, slow, writhing movements?

<p>Athetosis (B)</p> Signup and view all the answers

Which reflex mechanism remains intact in upper motor neuron injuries?

<p>Muscle reflexes (B)</p> Signup and view all the answers

What is the result of damage to the motor neurons in ALS?

<p>Progressive muscle weakening and atrophy (C)</p> Signup and view all the answers

Which area is primarily responsible for originating the lateral corticospinal tract?

<p>Precentral gyrus of the frontal lobe (D)</p> Signup and view all the answers

What is the role of muscle spindles in muscle function?

<p>Provide sensory information about muscle tension and length (A)</p> Signup and view all the answers

Which of the following statements about Golgi tendon organs is true?

<p>They transmit information about tendon tension. (A)</p> Signup and view all the answers

In the flexor reflex pathway, which of the following is NOT true?

<p>It requires input from the brain for motor response. (A)</p> Signup and view all the answers

Which response is indicative of upper motor neuron disease?

<p>Increased deep tendon reflexes (C)</p> Signup and view all the answers

What is a key characteristic of lower motor neuron disease?

<p>Decreased deep tendon reflexes (A)</p> Signup and view all the answers

Where do most motor fibers decussate within the corticospinal tract?

<p>In the lower medulla (A)</p> Signup and view all the answers

Which type of muscle spindle fiber detects slow increases in length or tension?

<p>Static sensory fibers (D)</p> Signup and view all the answers

What is the main function of the crossed extensor reflex?

<p>Extension of the opposite limb to facilitate balance (A)</p> Signup and view all the answers

What is the primary pathway for voluntary muscle control of the head and neck?

<p>Corticobulbar tracts (A)</p> Signup and view all the answers

Which of the following best describes the function of the corticospinal tract?

<p>Controls voluntary movement of skeletal muscles (A)</p> Signup and view all the answers

What role do gamma motor neurons primarily serve?

<p>Innervate intrafusal fibers within muscle spindles (A)</p> Signup and view all the answers

What is the primary neurotransmitter released by upper motor neurons?

<p>Glutamate (D)</p> Signup and view all the answers

How does the cerebellum contribute to motor functions?

<p>It determines the correct sequence of commands (D)</p> Signup and view all the answers

Which statement correctly differentiates between upper and lower motor neuron disorders?

<p>Lower motor neuron disorders primarily affect reflex arcs and their functioning. (A)</p> Signup and view all the answers

Which area of the brain is primarily involved in the planning and coordination of voluntary muscle movements?

<p>Supplementary motor area (C)</p> Signup and view all the answers

What type of motor functions does the reticulospinal tract primarily regulate?

<p>Muscle tone and posture control (A)</p> Signup and view all the answers

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

<p>It acts as a gateway for transforming intention into action. (C)</p> Signup and view all the answers

Which type of reflex arc mechanism involves both sensory neurons and interneurons?

<p>Polysynaptic reflexes (A)</p> Signup and view all the answers

What distinguishes the primary motor cortex from other motor areas in the cerebral cortex?

<p>It determines the goals of voluntary movement. (B)</p> Signup and view all the answers

Which of the following pathways is classified as an efferent pathway?

<p>Corticospinal tract (B)</p> Signup and view all the answers

What characteristic is true for both alpha and gamma motor neurons?

<p>They are involved in the innervation of skeletal muscle. (A)</p> Signup and view all the answers

What is the role of the Golgi tendon organs in muscle physiology?

<p>Detect changes in muscle tension and prevent injury. (D)</p> Signup and view all the answers

What type of movement is primarily coordinated by the premotor area of the brain?

<p>Complex movements that require pattern recognition. (B)</p> Signup and view all the answers

Which type of neural mechanism provides the foundation for both voluntary and reflex motor responses?

<p>Efferent pathways (B)</p> Signup and view all the answers

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Study Notes

Neurological Patterns of Paralysis

  • Above decussation: paralysis occurs on the opposite side of the body; below decussation: paralysis is on the same side.
  • Strokes causing injury above the decussation lead to contralateral symptoms.
  • Disorders categorized based on type of motor neuron involvement and injury level.

Motor Neuron Classes

  • Upper Motor Neurons (UMNs): Connect brain to spinal cord, reflexes intact, associated with conditions like thrombosis and degenerative diseases.
  • Lower Motor Neurons (LMNs): Connect spinal cord to muscles, leading to flaccid paralysis and no reflexes.

Clinical Movement Disorders

  • Ataxia: Difficulty coordinating muscle activity.
  • Athetosis: Slow, involuntary writhing movements.
  • Ballismus: Jerking and swinging motions of limbs.
  • Bradykinesia/Hypokinesia: Reduced movement spontaneity.
  • Chorea: Irregular, involuntary muscular movements.
  • Cogwheel Rigidity: Resistance to movement with a "catch".
  • Dystonia: Abnormal muscle tonicity, difficulty in posture maintenance.
  • Hyperkinesia: Excessive movements.
  • Tic: Repetitive muscle contractions that can be temporarily suppressed.
  • Tremor: Oscillating movements of muscles.

Cerebral Palsy Overview

  • Result of damage to UMNs from events like cerebral anoxia or hemorrhage.
  • Types based on motor dysfunction:
    • Spastic: Inability of muscles to relax.
    • Hemiplegia: One arm and one leg affected on the same side.
    • Diplegia: Both legs affected.
    • Quadriplegia: All extremities and neck muscles involved.
    • Athetoid/Dyskinetic: Inability to control movement.
    • Ataxic: Difficulty with balance and coordination.

Amyotrophic Lateral Sclerosis (ALS)

  • Degenerative neurologic disease affecting both UMNs and LMNs.
  • Rapid progression and fatal, with initial symptoms in arms and legs.

Spinal Cord Injury (SCI)

  • Impairs neural impulse transduction, affecting sensation and motor function.
  • Complete injury results in loss of sensation below the injury level.
  • Types of partial injuries include:
    • Central Cord Syndrome
    • Anterior Cord Syndrome
    • Brown-Sequard Syndrome: Loss of motor function on one side and pain/temperature on the other.

Motor Pathways and Their Functions

  • Corticobulbar Tracts: Control movements of the eyes, tongue, and speech.
  • Lateral Corticospinal Tract: Originates in the precentral gyrus; controls voluntary skeletal muscles.
  • Most fibers decussate at the lower medulla; some travel via ventral corticospinal tracts.

Intrinsic Muscle Control

  • Muscle Spindles: Detect changes in muscle length and prevent excessive stretch.
  • Golgi Tendon Organs: Monitor tension in tendon and rate of change.

Reflex Responses

  • Flexor Reflex: Withdrawal from painful stimuli, does not require input from the brain.
  • Crossed Extensor Reflex: Activate opposite limb to stabilize body during withdrawal.

Motor System Disorders

  • Upper Motor Neuron Disease: Increased tone, hyperreflexia, positive Babinski sign, spastic paralysis.
  • Lower Motor Neuron Disease: Decreased tone, hyporeflexia, negative Babinski sign, flaccid paralysis.

Sensory and Motor Pathways

  • Sensory Tracts: Dorsal column (fine touch), spinocerebellar (proprioception), spinothalamic (pain and temperature).
  • Motor Tracts: Corticospinal (voluntary movement), reticulospinal (posture and movement control).

Central Nervous System (CNS) and Motor Control

  • Primary motor cortex establishes movement goals; basal ganglia integrates movements while the cerebellum coordinates execution.
  • Motor pathways transmit signals from CNS to voluntary muscles, smooth muscles, and glands.

Specialized Motor Areas

  • Broca’s Area: Related to speech formulation and muscle control for speech.
  • Fields for eye movements and head rotations monitor and react to external stimuli.

Transmission Mechanisms

  • Corticospinal tract, a key output pathway for motor signals from the motor cortex to muscles, is crucial for voluntary control of movements.

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