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?

Loss of motor function on one side and pain/temp sensation on the other Signup and view all the answers

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

Lower motor neuron lesions lead to flaccid paralysis Signup and view all the answers

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

Loss of sensation and motor function below the level of injury Signup and view all the answers

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

Hyperkinesia Signup and view all the answers

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

Athetosis Signup and view all the answers

Which reflex mechanism remains intact in upper motor neuron injuries?

Muscle reflexes Signup and view all the answers

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

Progressive muscle weakening and atrophy Signup and view all the answers

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

Precentral gyrus of the frontal lobe Signup and view all the answers

What is the role of muscle spindles in muscle function?

Provide sensory information about muscle tension and length Signup and view all the answers

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

They transmit information about tendon tension. Signup and view all the answers

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

It requires input from the brain for motor response. Signup and view all the answers

Which response is indicative of upper motor neuron disease?

Increased deep tendon reflexes Signup and view all the answers

What is a key characteristic of lower motor neuron disease?

Decreased deep tendon reflexes Signup and view all the answers

Where do most motor fibers decussate within the corticospinal tract?

In the lower medulla Signup and view all the answers

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

Static sensory fibers Signup and view all the answers

What is the main function of the crossed extensor reflex?

Extension of the opposite limb to facilitate balance Signup and view all the answers

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

Corticobulbar tracts Signup and view all the answers

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

Controls voluntary movement of skeletal muscles Signup and view all the answers

What role do gamma motor neurons primarily serve?

Innervate intrafusal fibers within muscle spindles Signup and view all the answers

What is the primary neurotransmitter released by upper motor neurons?

Glutamate Signup and view all the answers

How does the cerebellum contribute to motor functions?

It determines the correct sequence of commands Signup and view all the answers

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

Lower motor neuron disorders primarily affect reflex arcs and their functioning. Signup and view all the answers

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

Supplementary motor area Signup and view all the answers

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

Muscle tone and posture control Signup and view all the answers

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

It acts as a gateway for transforming intention into action. Signup and view all the answers

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

Polysynaptic reflexes Signup and view all the answers

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

It determines the goals of voluntary movement. Signup and view all the answers

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

Corticospinal tract Signup and view all the answers

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

They are involved in the innervation of skeletal muscle. Signup and view all the answers

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

Detect changes in muscle tension and prevent injury. Signup and view all the answers

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

Complex movements that require pattern recognition. Signup and view all the answers

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

Efferent pathways Signup and view all the answers

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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Description

This quiz covers the effects of neurological injuries above and below the decussation point in the nervous system. It discusses the implications of strokes, classifications of disorders, and the characteristics of upper and lower motor neuron injuries. Test your knowledge on physiological responses and symptom manifestations related to various neurological conditions.