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Questions and Answers
What is the primary function of the corticospinal tracts?
What is the primary function of the corticospinal tracts?
Where do the corticospinal tract neurons primarily originate?
Where do the corticospinal tract neurons primarily originate?
What percentage of corticospinal fibers decussate at the caudal medulla?
What percentage of corticospinal fibers decussate at the caudal medulla?
Which part of the spinal cord do the fibers of the lateral corticospinal tract innervate?
Which part of the spinal cord do the fibers of the lateral corticospinal tract innervate?
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What is hereditary spastic paraparesis characterized by?
What is hereditary spastic paraparesis characterized by?
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Which cells in the primary motor cortex give rise to the largest-diameter corticospinal axons?
Which cells in the primary motor cortex give rise to the largest-diameter corticospinal axons?
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What term is used as an alternative name for the corticospinal tract?
What term is used as an alternative name for the corticospinal tract?
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Which structure does the corticospinal axons pass through after leaving the cerebral hemispheres?
Which structure does the corticospinal axons pass through after leaving the cerebral hemispheres?
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What is one potential cause of acute lesions in the spinal cord?
What is one potential cause of acute lesions in the spinal cord?
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Which symptom is associated with a lumbosacral spinal cord lesion?
Which symptom is associated with a lumbosacral spinal cord lesion?
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What clinical syndrome is produced by a hemilesion of the thoracic spinal cord?
What clinical syndrome is produced by a hemilesion of the thoracic spinal cord?
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What is the result of a lower cervical spinal cord lesion?
What is the result of a lower cervical spinal cord lesion?
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Which symptom is commonly seen with chronic compression of the spinal cord?
Which symptom is commonly seen with chronic compression of the spinal cord?
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Which characteristic is indicative of a high cervical cord lesion?
Which characteristic is indicative of a high cervical cord lesion?
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What type of lesion is commonly associated with multiple sclerosis?
What type of lesion is commonly associated with multiple sclerosis?
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Which of the following is NOT a cause of chronic spinal cord lesions?
Which of the following is NOT a cause of chronic spinal cord lesions?
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What is primarily affected by degeneration of the lateral funiculi in the thoracic spinal cord?
What is primarily affected by degeneration of the lateral funiculi in the thoracic spinal cord?
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Where do the majority of corticospinal neurones terminate?
Where do the majority of corticospinal neurones terminate?
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From where does the rubrospinal tract originate?
From where does the rubrospinal tract originate?
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Which of the following statements about the tectospinal tract is accurate?
Which of the following statements about the tectospinal tract is accurate?
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The vestibulospinal tracts are primarily responsible for mediating what effect?
The vestibulospinal tracts are primarily responsible for mediating what effect?
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Which nucleus is associated with the lateral vestibulospinal tract?
Which nucleus is associated with the lateral vestibulospinal tract?
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Which part of the spinal cord does the descending tectospinal fibers predominantly terminate?
Which part of the spinal cord does the descending tectospinal fibers predominantly terminate?
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Which structure provides visual input to the tectospinal tract?
Which structure provides visual input to the tectospinal tract?
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Study Notes
Descending Spinal Tracts
- Originate from the cerebral cortex and brainstem
- Control movement, muscle tone, spinal reflexes, spinal autonomic functions, and sensory transmission modulation
- Corticospinal tracts are involved in voluntary, skilled movements, especially in distal limbs
- Neurons originate in the cerebral cortex (motor and sensory cortices including the precentral gyrus)
- Corticospinal axons exit the cerebral hemispheres through the corona radiata and internal capsule, entering the crus cerebri
- The corticospinal tract fibres form pyramids in the medulla oblongata
- About 75-90% of fibres decussate (cross over) to the contralateral side and form the lateral corticospinal tract
- Remaining fibres (10-25%) remain ipsilateral and create the ventral corticospinal tract
- Fibres also decussate near their termination, enabling control of the contralateral side.
- Hereditary spastic paraparesis is an inherited degenerative disorder causing progressive leg weakness and stiff gait, with degeneration of lateral funiculi including the lateral corticospinal tract.
Rubrospinal Tract
- Originates in the red nucleus of the midbrain tegmentum
- Controls the tone of limb flexor muscles (excitatory)
- Receives afferent fibers from the motor cortex and cerebellum
- Represents a non-pyramidal route for motor cortex and cerebellum influence on spinal motor activity
Tectospinal Tract
- Arises from the superior colliculus of the midbrain
- Axons descend ventromedially and cross in the dorsal tegmental decussation
- Located near the ventral median fissure in the spinal cord, predominantly in cervical segments
- Mediates reflexes in response to visual stimuli
Vestibulospinal Tracts
- Originates from vestibular nuclei in the pons and medulla
- Receive input from the labyrinthine system and the cerebellum
- Lateral vestibulospinal tract originates from the lateral vestibular nucleus, descending ipsilaterally in the ventral funiculus
- Controls extensor muscle tone for posture maintenance
Reticulospinal Tracts
- Arise from the reticular formation of the pons and medulla
- Medial (pontine) tract – axons descend ipsilaterally
- Lateral (medullary) tract – axons descend bilaterally
- Located in the ventral funiculus
- Influence voluntary movement, reflex activity, muscle tone, and vital functions (pressor and depressor effects)
Lesions of the Spinal Cord
- Focal lesions (damage) disrupt function at segmental level, or interrupt descending/ascending tracts
- Clinical manifestations differ depending on the location and severity of injury to the spinal cord
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Description
Explore the anatomy and function of descending spinal tracts originating from the cerebral cortex and brainstem. This quiz covers aspects like corticospinal tract fibers, their decussation, and their role in voluntary muscle movement. Test your knowledge on the pathways involved in controlling motor functions and reflexes.
