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Questions and Answers
Which type of neuron in the descending pathway is also referred to as the final common pathway?
Which type of neuron in the descending pathway is also referred to as the final common pathway?
What is the location of the cell body of a 2nd order neuron in the descending pathway?
What is the location of the cell body of a 2nd order neuron in the descending pathway?
What type of contraction occurs in the quadriceps muscle when the patellar tendon is tapped using a neuro hammer?
What type of contraction occurs in the quadriceps muscle when the patellar tendon is tapped using a neuro hammer?
Which nerve carries the impulse from the stimulated muscle spindle to the spinal cord?
Which nerve carries the impulse from the stimulated muscle spindle to the spinal cord?
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What is the location of the cell body of a 1st order neuron in the descending pathway?
What is the location of the cell body of a 1st order neuron in the descending pathway?
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What is the function of the 3rd order neuron in the descending pathway?
What is the function of the 3rd order neuron in the descending pathway?
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What type of reflex arc is shown in the knee jerk/patellar tendon reflex?
What type of reflex arc is shown in the knee jerk/patellar tendon reflex?
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What is the location of the Ventral CST in the spinal cord?
What is the location of the Ventral CST in the spinal cord?
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What is the result of occlusion of the vessel supplying the area where CST fibers are closely packed together?
What is the result of occlusion of the vessel supplying the area where CST fibers are closely packed together?
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What is the location of the Lateral CST in the spinal cord?
What is the location of the Lateral CST in the spinal cord?
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What is the characteristic of a lacunar syndrome?
What is the characteristic of a lacunar syndrome?
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What is the effect of a spinal cord lesion on the body?
What is the effect of a spinal cord lesion on the body?
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What is the result of occlusion of the posterior limb of the internal capsule?
What is the result of occlusion of the posterior limb of the internal capsule?
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What is the result of occlusion of a bigger vessel in the brain?
What is the result of occlusion of a bigger vessel in the brain?
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Where do the rubrospinal tract fibers cross immediately?
Where do the rubrospinal tract fibers cross immediately?
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What is the function of the rubrospinal tract in the spinal cord?
What is the function of the rubrospinal tract in the spinal cord?
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In which Rexed laminae do the rubrospinal tract terminate?
In which Rexed laminae do the rubrospinal tract terminate?
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What is the origin of the tract that forms part of the MLF and is uncrossed?
What is the origin of the tract that forms part of the MLF and is uncrossed?
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Which tract terminates in the anterior horn of upper cervical levels of the spinal cord?
Which tract terminates in the anterior horn of upper cervical levels of the spinal cord?
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What is the characteristic of the fibers of the tract originating from the interstitial nucleus of Cajal?
What is the characteristic of the fibers of the tract originating from the interstitial nucleus of Cajal?
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In which part of the spinal cord do the rubrospinal tract fibers enter?
In which part of the spinal cord do the rubrospinal tract fibers enter?
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What is a characteristic of a patient with a left-sided LMN lesion?
What is a characteristic of a patient with a left-sided LMN lesion?
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What is a characteristic of a patient with a right UMN lesion?
What is a characteristic of a patient with a right UMN lesion?
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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?
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?
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What is a characteristic of a patient with a right LMN lesion?
What is a characteristic of a patient with a right LMN lesion?
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What is the difference between a left UMN lesion and a left LMN lesion?
What is the difference between a left UMN lesion and a left LMN lesion?
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What is the characteristic of a patient with Bell's palsy on the right side?
What is the characteristic of a patient with Bell's palsy on the right side?
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Which nucleus is the origin of the Rubrospinal tract?
Which nucleus is the origin of the Rubrospinal tract?
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Where do the fibers of the Interstitiospinal tract terminate?
Where do the fibers of the Interstitiospinal tract terminate?
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What is the function of the Tectobulbar tract?
What is the function of the Tectobulbar tract?
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In which part of the spinal cord do the fibers of the Tectospinal tract terminate?
In which part of the spinal cord do the fibers of the Tectospinal tract terminate?
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What is the course of fibers of the Rubrospinal tract?
What is the course of fibers of the Rubrospinal tract?
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What is the origin of the Tectospinal tract?
What is the origin of the Tectospinal tract?
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Where do the fibers of the Rubrospinal tract terminate?
Where do the fibers of the Rubrospinal tract terminate?
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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.
