Descending Spinal Tracts and Corticospinal Overview
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Questions and Answers

What is the primary focus of the corticospinal tracts?

  • Control of voluntary, skilled movements (correct)
  • Coordination of balance and posture
  • Control of involuntary muscle function
  • Regulation of sensory transmission
  • Where do corticospinal tract neurones originate?

  • Spinal cord
  • Cerebral cortex (correct)
  • Brainstem
  • Thalamus
  • What percentage of corticospinal tract fibers decussate at the caudal medulla?

  • 25% to 50%
  • 75% to 90% (correct)
  • 50% to 75%
  • 10% to 25%
  • What alternative name is used for the corticospinal tract?

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

    Which part of the spinal cord do the lateral corticospinal tracts primarily influence?

    <p>Contralateral side of the body (B)</p> Signup and view all the answers

    What is a characteristic feature of voluntary movements controlled by the corticospinal tracts?

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

    Hereditary spastic paraparesis primarily affects which part of the body?

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

    What is the genetic inheritance pattern of hereditary spastic paraparesis?

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

    What is primarily affected by degeneration of the lateral funiculi in the thoracic spinal cord?

    <p>Spastic paraparesis with hyperreflexia (D)</p> Signup and view all the answers

    Where does the majority of corticospinal neurones terminate?

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

    What role does the rubrospinal tract primarily serve in motor control?

    <p>Influence on limb flexor muscle tone (C)</p> Signup and view all the answers

    Which structure gives rise to the tectospinal tract?

    <p>Superior colliculus (C)</p> Signup and view all the answers

    What is the primary function of the lateral vestibulospinal tract?

    <p>Mediating powerful excitatory effects on extensor motor neurones (C)</p> Signup and view all the answers

    Which complex route is represented by the rubrospinal tract for influencing spinal motor activity?

    <p>Non-pyramidal route (A)</p> Signup and view all the answers

    What type of sensory input does the superior colliculus primarily receive?

    <p>Visual input (C)</p> Signup and view all the answers

    Where do tectospinal tract fibres primarily terminate in the spinal cord?

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

    What is the primary function of the medial vestibular nucleus?

    <p>Coordinating head and eye movements (C)</p> Signup and view all the answers

    Which descending tract originates from the red nucleus?

    <p>Rubrospinal tract (C)</p> Signup and view all the answers

    Which tracts are involved in controlling both alpha and gamma motor neurons?

    <p>Reticulospinal tracts (C)</p> Signup and view all the answers

    What type of movements does the corticospinal tract primarily control?

    <p>Discrete, skilled movements (A)</p> Signup and view all the answers

    Which tract is specifically involved in reflex responses to visual stimuli?

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

    Which vestibulospinal tract mediates excitation of limb extensor muscles?

    <p>Lateral vestibulospinal tract (D)</p> Signup and view all the answers

    How do pontine reticulospinal fibers descend through the spinal cord?

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

    What effect do reticulospinal tracts have on the circulatory system?

    <p>They exert pressor and depressor effects. (C)</p> Signup and view all the answers

    What is one way in which focal lesions of the spinal cord produce clinical manifestations?

    <p>They destroy function at the segmental level. (C)</p> Signup and view all the answers

    Which of the following correctly describes the result of a lumbosacral spinal cord lesion?

    <p>Weakness, areflexia of the lower limbs, and sensory loss. (D)</p> Signup and view all the answers

    What syndrome is associated with a hemilesion of the thoracic spinal cord?

    <p>Brown-Séquard syndrome. (B)</p> Signup and view all the answers

    What condition is commonly associated with subacute and chronic lesions of the spinal cord?

    <p>Multiple sclerosis. (C)</p> Signup and view all the answers

    Which of the following best describes the symptoms of a lower cervical spinal cord lesion?

    <p>Areflexia of the upper limbs and hyperreflexia in the lower limbs. (B)</p> Signup and view all the answers

    What is a key clinical manifestation of a high cervical spinal cord lesion?

    <p>Spastic tetraplegia and sensory loss below the lesion. (A)</p> Signup and view all the answers

    Which factor is NOT typically associated with chronic compression of the spinal cord?

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

    The interruption of which type of tracts is caused by lesions in the spinal cord?

    <p>Both descending motor and ascending sensory tracts. (B)</p> Signup and view all the answers

    Flashcards

    Rubrospinal Tract

    A descending motor pathway originating in the red nucleus of the midbrain, playing a role in controlling limb flexor muscle tone.

    Tectospinal Tract

    A descending motor pathway originating in the superior colliculus of the midbrain, mediating reflex movements in response to visual stimuli.

    Vestibulospinal Tract

    A descending motor pathway originating in the vestibular nuclei, situated in the pons and medulla, responsible for maintaining balance and posture.

    Lateral Vestibulospinal Tract

    This tract descends ipsilaterally in the ventral funiculus and exerts powerful excitatory effects on extensor motor neurons.

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    Lateral Corticospinal Tract

    A motor pathway connecting the motor cortex to the spinal cord, responsible for voluntary movement.

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    Degeneration of the Lateral Funiculi

    A condition characterized by spastic paraparesis (weakness in the legs), hyperreflexia (increased reflexes), and extensor plantar responses.

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    Red Nucleus Input

    The red nucleus of the midbrain receives input from both the motor cortex and the cerebellum.

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    Superior Colliculus Input

    The superior colliculus of the midbrain receives visual input.

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    Focal Spinal Cord Lesion

    A lesion that affects the spinal cord at a specific level, leading to disruptions in nerve function.

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    Descending Spinal Tracts

    Descending tracts of the spinal cord that originate from the cerebral cortex and brainstem, responsible for controlling movement, muscle tone, spinal reflexes, autonomic functions, and modulating sensory transmission.

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    Segmental Level Damage

    Damage to the spinal cord at a specific level, causing loss of function in that segment.

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    Corticospinal Tracts

    Tracts that primarily control voluntary, precise, and skilled movements, especially those of the limbs, often referred to as 'fractionated' movements.

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    Betz Cells

    Large nerve cells found in the precentral gyrus or primary motor cortex, responsible for initiating voluntary movements and contributing to the largest-diameter corticospinal axons.

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    Tract Interruption

    Interruption of nerve pathways that carry signals up and down the spinal cord.

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    Spinal Cord Syndrome

    A clinical syndrome caused by damage to specific parts of the spinal cord, leading to unique symptoms.

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    Corticospinal Axons

    Bundles of nerve fibers that travel from the cerebral cortex to the spinal cord, passing through subcortical structures, the midbrain, pons, and medulla.

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    Lumbosacral Spinal Cord Lesion Syndrome

    A syndrome characterized by weakness, muscle wasting, and decreased reflexes in the lower limbs, as well as sensory loss below the lesion.

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    Decussation

    The crossing over of nerve fibers from one side of the brain to the other side of the spinal cord, ensuring control of the opposite side of the body.

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    Brown-Séquard Syndrome

    A condition with ipsilateral (same side) loss of proprioception and upper motor neuron signs, and contralateral (opposite side) loss of pain and temperature sensation.

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    Lower Cervical Spinal Cord Lesion Syndrome

    A syndrome resulting in weakness, wasting, and decreased reflexes in the upper limbs, as well as spastic paraparesis and sensory loss below the lesion.

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    Ventral Corticospinal Tract

    The ventral corticospinal tract, responsible for controlling movement of the contralateral limbs, and located in the ventral part of the spinal white matter.

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    Upper Cervical Spinal Cord Lesion Syndrome

    A syndrome causing spastic tetraplegia, hyperreflexia, and sensory loss below the lesion.

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    Hereditary Spastic Paraparesis

    An inherited degenerative disorder affecting the legs, leading to weakness and stiffness, causing difficulty with walking.

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    Medial Vestibulospinal Tract

    A descending pathway from the vestibular nuclei that primarily controls the extensor muscles involved in maintaining posture.

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    Medial Longitudinal Fasciculus (MLF)

    A bundle of nerve fibers that connects the vestibular nuclei with nuclei controlling eye muscles, crucial for coordinating head and eye movements.

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    Reticulospinal Tracts

    Descending pathways originating from the reticular formation of the brainstem, influencing voluntary movement, reflexes, and muscle tone.

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    Reticulospinal Tracts

    Tracts that facilitate voluntary movement, control reflex activities, and regulate muscle tone, originating from the pons and medulla.

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    Study Notes

    Descending Spinal Tracts

    • Originate from cerebral cortex and brainstem
    • Control movement, muscle tone, spinal reflexes, spinal autonomic functions, and sensory transmission modulation
    • Include corticospinal tracts, rubrospinal tract, tectospinal tract, and vestibulospinal tracts

    Corticospinal Tracts

    • Control voluntary, skilled movements of distal limbs
    • Neurons originate in the cerebral cortex (motor & sensory)
    • Betz cells produce largest-diameter corticospinal axons
    • Pass through corona radiata and internal capsule to enter crus cerebri
    • Majority of fibers decussate to form the lateral corticospinal tract (75-90%), entering contralateral spinal white matter
    • Remaining fibers form the ventral corticospinal tract (10-25%), staying ipsilateral
    • Fiber decussation continues near their termination, effecting contralateral control

    Hereditary Spastic Paraparesis

    • Inherited degenerative disorder
    • Progressive weakness and stiffness of gait (legs)
    • Mainly affects lateral corticospinal tracts and related fiber bundles

    Rubrospinal Tract

    • Originates from red nucleus in midbrain
    • Excites motor neurons controlling flexor muscles
    • Receives input from motor cortex and cerebellum
    • Non-pyramidal route for influencing spinal motor activity

    Tectospinal Tract

    • Originates from superior colliculus of midbrain
    • Passes ventromedially, crossing in dorsal tegmental decussation
    • Terminates in cervical segments, controlling reflex movements in response to visual stimuli
    • Receives input from superior colliculus

    Vestibulospinal Tracts

    • Originates from vestibular nuclei in pons and medulla
    • Lateral vestibulospinal tract arises from the lateral vestibular nucleus, descending ipsilaterally in the ventral funiculus
    • Excites extensor motor neurons to maintain posture (anti-gravity)

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    Description

    Explore the intricacies of descending spinal tracts, including their origins, functions, and distinctions among the corticospinal tracts. This quiz also delves into hereditary spastic paraparesis, providing insight into hereditary degenerative disorders affecting motor control. Test your knowledge on the essential connections between the brain and the spinal cord.

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