Neurons in the Descending Pathway
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Neurons in the Descending Pathway

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Questions and Answers

Which type of neuron in the descending pathway is also referred to as the final common pathway?

  • 1st order neuron
  • 4th motor neuron
  • 3rd order neuron (correct)
  • 2nd order neuron

    • What is the location of the cell body of a 2nd order neuron in the descending pathway?

  • Spinal nerve
  • Cerebral cortex
  • Anterior gray column of the spinal cord (correct)
  • Femoral nerve

    • What type of contraction occurs in the quadriceps muscle when the patellar tendon is tapped using a neuro hammer?

  • Slow and controlled contraction
  • Reflexive contraction
  • Jerk-like muscle contraction (correct)
  • Voluntary muscle contraction

    • Which nerve carries the impulse from the stimulated muscle spindle to the spinal cord?

    <p>Femoral nerve</p> Signup and view all the answers

    What is the location of the cell body of a 1st order neuron in the descending pathway?

    <p>Cerebral cortex</p> Signup and view all the answers

    What is the function of the 3rd order neuron in the descending pathway?

    <p>To stimulate skeletal muscles</p> Signup and view all the answers

    What type of reflex arc is shown in the knee jerk/patellar tendon reflex?

    <p>Monosynaptic reflex arc</p> Signup and view all the answers

    What is the location of the Ventral CST in the spinal cord?

    <p>Anterior funiculus</p> Signup and view all the answers

    What is the result of occlusion of the vessel supplying the area where CST fibers are closely packed together?

    <p>Dense manifestation of symptoms, including paralysis or weakness of arms, trunk, and legs</p> Signup and view all the answers

    What is the location of the Lateral CST in the spinal cord?

    <p>Lateral funiculus</p> Signup and view all the answers

    What is the characteristic of a lacunar syndrome?

    <p>Small infarcts in the subcortical areas of the brain</p> Signup and view all the answers

    What is the effect of a spinal cord lesion on the body?

    <p>Paralysis on the ipsilateral side of the body</p> Signup and view all the answers

    What is the result of occlusion of the posterior limb of the internal capsule?

    <p>Purely motor deficit</p> Signup and view all the answers

    What is the result of occlusion of a bigger vessel in the brain?

    <p>Both motor and sensory deficit</p> Signup and view all the answers

    Where do the rubrospinal tract fibers cross immediately?

    <p>Ventral tegmental decussation</p> Signup and view all the answers

    What is the function of the rubrospinal tract in the spinal cord?

    <p>Modulation of reflex postural movements in response to visual and auditory stimuli</p> Signup and view all the answers

    In which Rexed laminae do the rubrospinal tract terminate?

    <p>Rexed laminae V, VI, VII</p> Signup and view all the answers

    What is the origin of the tract that forms part of the MLF and is uncrossed?

    <p>Interstitial nucleus of Cajal</p> Signup and view all the answers

    Which tract terminates in the anterior horn of upper cervical levels of the spinal cord?

    <p>Tract originating from the interstitial nucleus of Cajal</p> Signup and view all the answers

    What is the characteristic of the fibers of the tract originating from the interstitial nucleus of Cajal?

    <p>They are uncrossed</p> Signup and view all the answers

    In which part of the spinal cord do the rubrospinal tract fibers enter?

    <p>Lateral funiculus</p> Signup and view all the answers

    What is a characteristic of a patient with a left-sided LMN lesion?

    <p>Inability to move the left half of the face</p> Signup and view all the answers

    What is a characteristic of a patient with a right UMN lesion?

    <p>Inability to move the left lower half of the face</p> Signup and view all the answers

    What is the location of the lesion in a patient who is unable to move the left lower half of the face but can still wrinkle both eyebrows?

    <p>Left UMN</p> Signup and view all the answers

    What is a characteristic of a patient with a right LMN lesion?

    <p>Inability to move the right lower half of the face</p> Signup and view all the answers

    What is the difference between a left UMN lesion and a left LMN lesion?

    <p>Location of the lesion, with UMN lesions affecting the upper motor neurons and LMN lesions affecting the lower motor neurons</p> Signup and view all the answers

    What is the characteristic of a patient with Bell's palsy on the right side?

    <p>No creases on the right side of the face, and nose is skewed to the left side</p> Signup and view all the answers

    Which nucleus is the origin of the Rubrospinal tract?

    <p>Red nucleus</p> Signup and view all the answers

    Where do the fibers of the Interstitiospinal tract terminate?

    <p>Internuncial neurons of all spinal cord levels</p> Signup and view all the answers

    What is the function of the Tectobulbar tract?

    <p>Mediate reflex postural movements of head and neck in response to visual stimuli</p> Signup and view all the answers

    In which part of the spinal cord do the fibers of the Tectospinal tract terminate?

    <p>Anterior horn of upper cervical spinal cord</p> Signup and view all the answers

    What is the course of fibers of the Rubrospinal tract?

    <p>Cross in ventral tegmental decussation</p> Signup and view all the answers

    What is the origin of the Tectospinal tract?

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

    Where do the fibers of the Rubrospinal tract terminate?

    <p>Internuncial neurons of all spinal cord levels</p> Signup and view all the answers

    Study Notes

    Descending Pathway

    • Consists of 1st order, 2nd order, and 3rd order neurons
    • Originates from cerebral cortex, anterior gray column of the spinal cord, and anterior gray column of the spinal cord
    • Axons of 1st order neurons can terminate directly on 3rd order neurons, such as in reflex arcs

    Corticospinal Tract (CST)

    • AKA Pyramidal Tract
    • Originates from cerebral cortex
    • Fibers are closely packed together, making them susceptible to damage from occlusion of a single vessel
    • Spinal cord lesions can produce paralysis on the ipsilateral side of the body
    • Ventral CST is located at the anterior funiculus, while lateral CST is located at the lateral funiculus of the spinal cord

    Clinical Correlation

    • Lacunar syndrome: small infarcts in the subcortical areas of the brain, resulting in motor or sensory deficits
    • Occlusion of a larger vessel can cause both motor and sensory deficits

    Rubrospinal Tract

    • Originates from the red nucleus in the midbrain
    • Fibers cross immediately in the ventral tegmental decussation and descend to the lateral funiculus of the spinal cord
    • Terminates in synapses with internuncial neurons in all spinal cord levels
    • Modulates reflex postural movements in response to visual and auditory stimuli

    Tectospinal and Tectobulbar Tracts

    • Originates from the interstitial nucleus of Cajal
    • Fibers are uncrossed and form part of the MLF
    • Terminates in the anterior horn of upper cervical levels of the spinal cord
    • Modulates reflex postural movements in response to visual and auditory stimuli

    Bell's Palsy

    • AKA Facial Nerve Palsy
    • Caused by LMN lesion
    • Presents with weakness on one side of the face, including the eyebrow, nose, and mouth
    • Prognosis is good, with >85% of patients experiencing spontaneous recovery within 1-2 months

    Hypoglossal Nucleus

    • Originates from the hypoglossal nucleus in the midbrain
    • Modulates reflex postural movements of the head and neck in response to visual and vestibular stimuli

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    Description

    Test your understanding of neurons in the descending pathway, including 1st, 2nd, and 3rd order neurons, their origins, and functions in monosynaptic reflex arcs.

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