Neurology: Descending Spinal Tracts Overview

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Questions and Answers

What is the primary function of the descending tracts of the spinal cord?

Regulation of autonomic functions

Sensation processing from the periphery

Control of movement and muscle tone (correct)

Coordination of visual and auditory reflexes

Which area of the brain is associated with the origin of corticospinal tract neurons?

Precentral gyrus (correct)

Temporal lobe

Cerebellum

Occipital lobe

Which term is commonly used as an alternative name for the corticospinal tract?

Cerebellar cortex tract

Pyramidal tract (correct)

Extrapyramidal tract

Spinal motor tract

What percentage of corticospinal fibres decussate in the caudal medulla?

75% to 90% Signup and view all the answers

What is the result of the decussation of corticospinal fibres?

Control of distal limbs on the opposite side Signup and view all the answers

In hereditary spastic paraparesis, what is the primary clinical manifestation?

Marked stiffness of gait Signup and view all the answers

What anatomical structure do corticospinal axons pass through after leaving the cerebral hemispheres?

Intracapsular fibre systems Signup and view all the answers

What is the inheritance pattern of hereditary spastic paraparesis?

Autosomal dominant Signup and view all the answers

What is the primary function of the medial vestibular nucleus?

Controlling extensor muscle tone for posture Signup and view all the answers

What do the reticulospinal tracts primarily influence?

Reflex activities and muscle tone Signup and view all the answers

Where do most corticospinal tracts decussate?

In the medullary pyramid Signup and view all the answers

Which tract is responsible for controlling limb flexor muscles?

Rubrospinal tract Signup and view all the answers

Which statement is true about the vestibulospinal tracts?

They mediate excitation of limb extensor muscles. Signup and view all the answers

What role do the reticulospinal fibres play in relation to the circulatory system?

They influence pressor and depressor effects. Signup and view all the answers

Which of the following tracts is involved in reflex responses to visual input?

Tectospinal tract Signup and view all the answers

Which descending tract primarily controls discrete, skilled movements of the distal extremities?

Corticospinal tract Signup and view all the answers

What deficits are primarily observed in patients with degeneration of the lateral funiculi?

Spastic paraparesis and hyperreflexia Signup and view all the answers

Where do the majority of corticospinal neurons terminate?

Cervical levels Signup and view all the answers

Which structure gives rise to the rubrospinal tract?

Red nucleus Signup and view all the answers

What is the primary role of the tectospinal tract?

Mediating reflex movements in response to visual stimuli Signup and view all the answers

Which of the following fibers have an excitatory effect on limb flexor muscles?

Rubrospinal tract fibers Signup and view all the answers

Which tract is primarily involved in maintaining extensor muscle tone?

Vestibulospinal tract Signup and view all the answers

What type of input does the superior colliculus receive?

Visual input Signup and view all the answers

Where do the descending tectospinal fibres predominantly terminate?

Cervical segments Signup and view all the answers

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

They interrupt descending motor and ascending sensory tracts. Signup and view all the answers

What characterizes the Brown–Séquard syndrome resulting from a hemilesion of the thoracic spinal cord?

Ipsilateral loss of proprioception and upper motor neurone signs. Signup and view all the answers

A lumbosacral spinal cord lesion is likely to cause which of the following symptoms?

Areflexia of the lower limbs and sensory loss below the lesion. Signup and view all the answers

What is a common cause of chronic compression of the spinal cord?

Tumours of the spine or prolapsed intervertebral discs. Signup and view all the answers

Which clinical sign is associated with lower cervical spinal cord lesions?

Hyperreflexia and extensor plantar responses in the lower limbs. Signup and view all the answers

What is the primary impact of acute lesions of the spinal cord?

Loss of function at the segmental level. Signup and view all the answers

Which condition is commonly associated with subacute and chronic spinal cord lesions?

Multiple sclerosis. Signup and view all the answers

High cervical cord lesions are associated with which of the following symptoms?

Spastic tetraplegia and sensory ataxia. Signup and view all the answers

Study Notes

Descending Spinal Tracts

Originate from the cerebral cortex and brainstem
Control movement, muscle tone, spinal reflexes, spinal autonomic functions, and sensory transmission to higher centers
Include corticospinal, rubrospinal, tectospinal, and vestibulospinal tracts

Corticospinal Tracts

Control voluntary, skilled movements, especially distal limb movements
Neurons originate in the cerebral cortex (motor and sensory cortices, including the precentral gyrus, or primary motor cortex)
Betz cells produce the largest-diameter corticospinal axons
Axons exit the cerebral hemispheres through the corona radiata and internal capsule, entering the crus cerebri of the midbrain
Most (75-90%) decussate (cross over) in the medulla to form the lateral corticospinal tract (controlling contralateral side of the body)
Remaining axons enter the ventral corticospinal tract (ipsilateral), with decussation near their termination.

Hereditary Spastic Paraparesis

Inherited degenerative disorder
Autosomal dominant pattern of inheritance
Progressive weakness and stiffness of gait, affecting the legs (usually)
Characterized by degeneration of the lateral funiculi, primarily the lateral corticospinal tract

Rubrospinal Tract

Originates from the red nucleus of the midbrain
Controls limb flexor muscles (excitatory)
Receives input from the motor cortex and cerebellum

Tectospinal Tract

Originates from the superior colliculus of the midbrain
Involved in reflex movements in response to visual stimuli
Descends, crossing in the dorsal tegmental decussation, and terminates primarily in cervical segments

Vestibulospinal Tracts

Originate from vestibular nuclei in the pons and medulla
Receive input from the labyrinthine system and cerebellum
Lateral vestibulospinal tract (ipsilateral): Excites extensor muscles, controlling posture
Medial vestibulospinal tract (ipsilateral): Located within the medial longitudinal fasciculus, contributes to eye and head movements

Reticulospinal Tracts

Originate from the reticular formation of the pons and medulla
Bilateral descending fibres (lateral or medullary reticulospinal tracts).
Involved in controlling voluntary movements, reflex activity, muscle tone, blood pressure, and breathing

Lesions of the Spinal Cord

Focal lesions can affect functions at the segmental level or interrupt descending motor or ascending sensory tracts
Different spinal cord lesions (e.g., lumbosacral, lower cervical, upper cervical) result in distinct clinical manifestations like weakness, loss of sensory function, or incoordination (ataxia).

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Description

This quiz covers the crucial aspects of descending spinal tracts, including their origin, function, and key types like corticospinal tracts. Dive into the details of voluntary movement control, reflexes, and the effects of hereditary conditions on these neural pathways. Test your knowledge on the anatomical and functional implications of these spinal tracts.