Spinal Cord Part II: White Matter

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Questions and Answers

What percentage of the total corticospinal tract does the Medial (Anterior) Corticospinal Tract comprise?

10% (correct)

15%

20%

Which part of the spinal cord does the Lateral Corticospinal Tract synapse in?

Lumbar region only

Cervical region only

Dorsal horn

Ventral horn's lateral region (correct)

In which location does the Medial (Anterior) Corticospinal Tract not cross?

Pyramids of the medulla (correct)

Spinal cord

Internal capsule

Cervicomedullary junction

What types of muscles does the Anterior (Medial) Corticospinal Tract primarily convey information to?

Neck, shoulder, and trunk Signup and view all the answers

Where does the Lateral Corticospinal Tract decussate?

At the pyramidal decussation Signup and view all the answers

What is the primary function of ascending tracts in the spinal cord?

To carry sensory information to the brain Signup and view all the answers

Which of the following is NOT classified as a descending tract?

Spinothalamic tract Signup and view all the answers

The term 'funiculus' refers to which of the following in the spinal cord?

Columns of axons Signup and view all the answers

What distinguishes the dorsal column from the anterolateral pathways?

They differ in sensory information processing locations Signup and view all the answers

Which statement is true regarding the location of reflex arcs in relation to spinal tracts?

Reflex arcs can function independently without cortical input Signup and view all the answers

The fasciculus cuneatus is primarily associated with which type of information?

Upper body sensory information Signup and view all the answers

How many orders of neurons are typically involved in the ascending pathways?

Three orders of neurons Signup and view all the answers

Which pathway is part of the lateral motor system?

Corticospinal tract Signup and view all the answers

What is a common cause of Brown-Sequard syndrome?

Penetrating injury Signup and view all the answers

What is a key characteristic of Central Cord Syndrome?

Symptoms vary based on the size of the affected area Signup and view all the answers

What typically causes Anterior Cord Syndrome?

Occlusion of the anterior spinal artery Signup and view all the answers

In Posterior Cord Syndrome, which type of injury can lead to the condition?

Penetrating or posterior spinal artery occlusion Signup and view all the answers

What is the main clinical sign of grey matter involvement in spinal cord injuries?

Symptoms solely at the level of injury Signup and view all the answers

What is the primary function of the Dorsal Column Medial Lemniscus pathway?

Proprioception and discriminative touch Signup and view all the answers

Which of the following best describes the pathways taken by sensory neurons in the Anterolateral Spinothalamic tract?

They decussate at the level of the spinal cord and then project to the thalamus. Signup and view all the answers

What is the main role of the Spinocerebellar tract?

Delivering unconscious proprioceptive information. Signup and view all the answers

Which tract is primarily responsible for fine motor control in distal extremities?

Lateral Corticospinal Tract Signup and view all the answers

What percentage of fibers in the Corticospinal Tract form the Lateral Corticospinal Tract?

90% Signup and view all the answers

The medial system of descending pathways is primarily involved in which activity?

Maintaining posture and trunk movements Signup and view all the answers

Which structure is primarily responsible for regulating precise motor skills in the lateral system?

Corticospinal Tract Signup and view all the answers

What is a key feature of the Lateral Corticospinal Tract?

It enables fractionation of movement. Signup and view all the answers

What is the primary origin of the Rubrospinal tract?

Red nucleus of the midbrain Signup and view all the answers

Which of the following best describes the role of the Pontine Reticulospinal tract?

Enhances antigravity reflexes Signup and view all the answers

What physiological function is primarily affected by damage to the Vestibulospinal tract?

Balance and posture Signup and view all the answers

Where does the Tectospinal tract originate?

Superior colliculus Signup and view all the answers

What is a key characteristic of the Lateral Vestibulospinal tract?

Facilitates extensors and inhibits flexors Signup and view all the answers

Which pathway is a part of the Medial Activation system?

Reticulospinal tract Signup and view all the answers

What happens to voluntary movements when the Rubrospinal tract is impaired?

They become slower and less accurate Signup and view all the answers

Which tracts are included in the lateral activation system?

Rubrospinal and Corticospinal tracts Signup and view all the answers

How does the Vestibulospinal tract react to stimuli from the vestibular apparatus?

Facilitates neck and upper back muscles Signup and view all the answers

Which arteries provide the longitudinal vascular supply to the spinal cord?

One anterior spinal artery and two posterior arteries Signup and view all the answers

What is the primary role of descending tracts in the spinal cord?

Transmit motor signals from the brain to the body Signup and view all the answers

Which columns of the white matter are primarily responsible for carrying sensory information?

Dorsal Column Medial Lemniscus Signup and view all the answers

What does the term 'fasciculus' refer to in the context of spinal cord anatomy?

Small bundles of nerve fibers Signup and view all the answers

The rubrospinal tract is primarily associated with which function?

Controlling voluntary fine motor movements Signup and view all the answers

How do descending tracts typically influence motor control?

By directly stimulating upper motor neurons Signup and view all the answers

The term 'funiculus' refers to which structure in the spinal cord?

A large nerve bundle or column Signup and view all the answers

What is one of the key similarities between the Dorsal Column and the Anterolateral pathways?

Both synapse in contralateral thalamic nuclei Signup and view all the answers

Which of the following is NOT a type of descending tract identified in the spinal cord?

Anterolateral tract Signup and view all the answers

What is the primary pathway through which the Lateral Corticospinal Tract travels after arising from motor areas?

Through the Internal Capsule Signup and view all the answers

What function is primarily associated with the Medial (Anterior) Corticospinal Tract?

Activating trunk and shoulder muscles Signup and view all the answers

In which part of the spinal cord does the Medial (Anterior) Corticospinal Tract primarily synapse?

Lamina IX of the ventral horn Signup and view all the answers

Which of the following accurately describes the pathway of the Lateral Corticospinal Tract from the motor cortex?

Motor cortex → Internal Capsule → Basis Pedunculi → Medulla → Lateral white matter Signup and view all the answers

What distinguishes the Medial (Anterior) Corticospinal Tract in its pathway compared to other corticospinal tracts?

It does not cross in the pyramids at all Signup and view all the answers

What is the primary cause of Anterior Cord Syndrome?

Occlusion of the anterior spinal artery Signup and view all the answers

Which of the following spinal cord injury syndromes is characterized by symptoms only at the level of injury?

Posterior Cord Syndrome Signup and view all the answers

In Central Cord Syndrome, which type of involvement leads to deficits below the level of injury?

Partial involvement of white matter pathways Signup and view all the answers

The symptoms of Brown-Sequard syndrome are typically the result of what type of injury?

Penetrating injury to one side of the spinal cord Signup and view all the answers

What is a common condition that can cause Central Cord Syndrome?

Syrinx formation in the central canal Signup and view all the answers

What is the primary function of the Dorsal Column Medial Lemniscus pathway?

Proprioception and discriminative touch Signup and view all the answers

Which structure specifically handles unconscious proprioceptive information?

Spinocerebellar Tract Signup and view all the answers

What percentage of fibers form the Lateral Corticospinal Tract within the Corticospinal Tract?

90% Signup and view all the answers

What is a key characteristic of the lateral activation system?

Regulates fine, precise motor skills Signup and view all the answers

Which descending pathway is primarily involved in trunk movement and postural control?

Anterior Corticospinal Tract Signup and view all the answers

Which tract is critical for the ability to perform tasks requiring fine motor control, like playing the piano?

Lateral Corticospinal Tract Signup and view all the answers

Which of the following statements accurately describes the primary function of the Anterolateral Spinothalamic tract?

Transmits pain and temperature sensations Signup and view all the answers

What is the term for the organization of sensory and motor information according to body regions?

Somatotopic organization Signup and view all the answers

What is the primary outcome of damage to the Rubrospinal tract?

Poor fractional movement of arms and hands Signup and view all the answers

Which of the following functions is NOT associated with the Reticulospinal tract?

Regulating sensory information from the vestibular apparatus Signup and view all the answers

How does the Medial Vestibulospinal tract contribute to head stability?

Enhances neck and upper back muscle control Signup and view all the answers

What role does the Lateral Vestibulospinal tract play in balance?

Facilitates extensors and inhibits flexors Signup and view all the answers

What stimuli does the Tectospinal tract primarily respond to?

Visual and auditory information Signup and view all the answers

Which statement best describes the role of the Pontine Reticulospinal tract?

Enhances antigravity reflexes to maintain posture Signup and view all the answers

Where does the Rubrospinal tract primarily decussate?

In the pons, joining the corticospinal tract Signup and view all the answers

Which artery contributes to the longitudinal vascular supply of the spinal cord?

Anterior spinal artery and two posterior arteries Signup and view all the answers

What is the primary function of the Medial Corticospinal tract?

Conveying control over axial and proximal muscles Signup and view all the answers

What is a likely consequence of damage to the vestibulospinal tracts?

Ataxia and balance problems Signup and view all the answers

Study Notes

White Matter Overview

Composed of columns of axons organized as ascending (afferent) and descending (efferent) tracts.
Ascending tracts transmit sensory information to the brain.
Descending tracts convey motor signals from the brain to the body.

Tract Definitions

Fasciculus: Small bundles of nerve fibers (axons).
Tract: Bundles of upper motor neuron axons traveling together in the white matter.

Major Spinal Cord Tracts

Ascending Tracts (Somatosensory):
- Anterolateral
- Spinothalamic
- Dorsal Column Medial Lemniscus
  - Fasciculus Cuneatus: Upper extremity sensation.
  - Fasciculus Gracilis: Lower extremity sensation.
- Spinocerebellar
Descending Tracts (Motor):
- Lateral Pathways:
  - Corticospinal
  - Rubrospinal
- Ventromedial Pathways:
  - Reticulospinal (Medullary and Pontine)
  - Vestibulospinal
  - Tectospinal

Organization of Spinal Cord Cross Section

Dorsal column contains sensory pathways.
Lateral motor system encompasses upper and lower extremity control.

Pathway Comparisons

Dorsal Column vs. Anterolateral Pathways:
- Both influence contralateral thalamic nuclei and the somatosensory cortex.
- Differ in synapsing structures, crossing over, and locations in the pathway.

Dorsal Column Medial Lemniscus

Functions in proprioception and discriminative touch.
Contains two primary parts: Fasciculus gracilis (lower extremity) and Fasciculus cuneatus (upper extremity).

Anterolateral Pathway

Primarily involves pain, temperature, and crude touch sensations.
Sensory neurons synapse in spinal cord dorsal horn and immediately decussate at their level.

Spinocerebellar Tract

Conveys unconscious proprioceptive information from the body to the cerebellum.

Descending (Motor) Pathways

Composed of upper motor neurons, split into lateral and medial systems.

Lateral System

Responsible for fine, precise motor skills in distal extremities.
Includes the Lateral Corticospinal Tract (90% of fibers) and the Rubrospinal Tract.

Medial System

Coordinated trunk movement and stabilization of proximal muscles.
Includes Reticulospinal, Vestibulospinal, and Tectospinal Tracts.

Corticospinal Tract Pathways

Lateral Corticospinal Tract: Controls fine movement of distal extremities; decussates at the cervicomedullary junction.
Medial (Anterior) Corticospinal Tract: Involved with neck, shoulder, and trunk muscle control; does not cross in the pyramids.

Functional Characteristics

Rubrospinal Tract: Facilitates upper extremity movement; decussates in the pons.
Lateral Corticospinal/Rubrospinal Impairments: Results in poor fractionated movements and slower, less accurate voluntary actions.

Ventromedial Pathways

Facilitate responses to balance and posture; includes both Reticulospinal and Vestibulospinal tracts.

Vestibulospinal Tract Functions

Integrates sensory information on head position for balance.
Damage leads to ataxia and balance problems.

Tectospinal Tract

Involved in reflexive head movements based on visual and auditory stimuli; crosses at the tectobulbospinal junction.

Vascular Supply to Spinal Cord

Comprised of one anterior spinal artery and two posterior arteries plus segmental medullary arteries; crucial for maintaining spinal cord function.

Clinical Implications of Spinal Cord Injury

Central Cord Syndrome: Symptoms vary based on the extent of white/grey matter involvement.
Anterior Cord Syndrome: Typically results from anterior spinal artery occlusion.
Brown-Sequard Syndrome: Caused by penetrating injuries.
Posterior Cord Syndrome: Can occur due to posterior spinal artery occlusion.

Key Concepts

Understanding the anatomy and organization of spinal cord pathways aids in diagnosing and managing spinal cord injuries.

White Matter Overview

Consists of columns of axons divided into ascending (sensory) and descending (motor) tracts.
Ascending tracts carry sensory information to the brain while descending tracts transmit motor commands from the brain.

Spinal Cord Tracts

Ascending Tracts include:
- Anterolateral and Spinothalamic Tracts for pain, temperature, and crude touch.
- Dorsal Column Medial Lemniscus for proprioception and discriminative touch.
- Spinocerebellar Tract for unconscious proprioceptive information.
Descending Tracts:
- Lateral pathways (Corticospinal and Rubrospinal Tracts) control precise movements in distal extremities.
- Ventromedial pathways (Reticulospinal, Vestibulospinal, Tectospinal) manage trunk movements and postures.

Dorsal Column Medial Lemniscus

Responsible for proprioception and discriminative touch.
Comprised of Fasciculus Gracilis for lower extremity and Fasciculus Cuneatus for upper extremity.
Follows a somatotopic organization for processing sensory information.

Anterolateral Pathway

Processes pain, temperature, and crude touch via sensory neurons that synapse in the dorsal horn of the spinal cord.
Axons cross the spinal cord immediately, projecting directly to the thalamus.

Lateral Corticospinal Tract

Contains 90% of corticospinal fibers; responsible for fine control of distal extremities.
Allows for fractionated movements enabling tasks such as typing or picking up small objects.
Pathway includes primary motor cortex, internal capsule, and various brainstem regions before decussating at the cervicomedullary junction.

Medial (Anterior) Corticospinal Tract

Originates in the frontal lobe and parietal lobe somatosensory area, involving the anterior spinal cord but does not cross in the pyramids.
Mainly conveys motor commands to neck, shoulder, and trunk muscles.

Rubrospinal Tract

Originates from the red nucleus of the midbrain and decussates in the pons.
Plays a role in controlling upper extremity movements.

Ventromedial Pathways

Include Reticulospinal (influences posture and antigravity reflexes), Vestibulospinal (maintains balance), and Tectospinal Tract (coordinates head movements in response to visual stimuli).

Vascular Supply to the Spinal Cord

Consists of one anterior spinal artery and two posterior spinal arteries supported by segmental medullary arteries.
Disruption in vascular supply due to trauma can lead to spinal cord injuries.

Spinal Cord Injury Syndromes

Central Cord Syndrome: Characterized by impairments related to the white matter involvement and potential somatotopic organization issues.
Anterior Cord Syndrome: Typically results from anterior spinal artery occlusion.
Brown-Sequard Syndrome: Often results from penetrating injuries affecting unilateral pathways.
Posterior Cord Syndrome: May arise from occlusion of the posterior spinal artery, encompassing all tracts below the injury level.

Clinical Implications

Understanding tract pathways and their functions aids in predicting outcomes and rehabilitation strategies following spinal injuries.

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Description

Explore the intricacies of the spinal cord's white matter in this quiz. Delve into the functions of ascending and descending tracts, and understand how they facilitate communication between the body and brain. Gain insights into the structure of funiculi and fasciculi, integral to the nervous system.