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Questions and Answers
What is the expected reflex response in a patient with a lower motor neuron (LMN) lesion?
What is the expected reflex response in a patient with a lower motor neuron (LMN) lesion?
A lesion in which structure causes hyperreflexia?
A lesion in which structure causes hyperreflexia?
Which statement best describes the impact of a cerebellar lesion on muscle strength?
Which statement best describes the impact of a cerebellar lesion on muscle strength?
A patient presents with ataxia. Where is the most probable location of the lesion?
A patient presents with ataxia. Where is the most probable location of the lesion?
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What type of paralysis results from an upper motor neuron (UMN) lesion?
What type of paralysis results from an upper motor neuron (UMN) lesion?
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What is a key characteristic of flaccid paralysis?
What is a key characteristic of flaccid paralysis?
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Where does the corticospinal tract synapse?
Where does the corticospinal tract synapse?
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If a patient has a cerebellar lesion on the right side of their brain, on which side will their ataxia be observed?
If a patient has a cerebellar lesion on the right side of their brain, on which side will their ataxia be observed?
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A lesion in the corticobulbar tract results in what type of facial palsy?
A lesion in the corticobulbar tract results in what type of facial palsy?
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In the case of a lower motor neuron lesion, what is the primary characteristic of the affected muscles?
In the case of a lower motor neuron lesion, what is the primary characteristic of the affected muscles?
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If the left motor cortex is damaged, which side of the face will show symptoms in central palsy?
If the left motor cortex is damaged, which side of the face will show symptoms in central palsy?
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Damage to the lower motor neuron (LMN) results in what specific outcome?
Damage to the lower motor neuron (LMN) results in what specific outcome?
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What is the final common pathway as described in the text?
What is the final common pathway as described in the text?
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An occlusion of the anterior cerebral artery (ACA) would most likely result in which of the following?
An occlusion of the anterior cerebral artery (ACA) would most likely result in which of the following?
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The upper motor neuron (UMN) is analogous to what in the context of controlling the lower motor neuron (LMN)?
The upper motor neuron (UMN) is analogous to what in the context of controlling the lower motor neuron (LMN)?
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Which neurotransmitter is primarily associated with the direct activation pathways in the motor system?
Which neurotransmitter is primarily associated with the direct activation pathways in the motor system?
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How are the upper and lower face innervated by the facial nerve?
How are the upper and lower face innervated by the facial nerve?
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What differentiates peripheral facial palsy from central facial palsy regarding the side of the lesion?
What differentiates peripheral facial palsy from central facial palsy regarding the side of the lesion?
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Fibers from the primary motor cortex pass through which structure before diverging into the corticospinal and corticobulbar tracts?
Fibers from the primary motor cortex pass through which structure before diverging into the corticospinal and corticobulbar tracts?
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A lesion in the posterior limb of the internal capsule would most likely result in which of the following?
A lesion in the posterior limb of the internal capsule would most likely result in which of the following?
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In the spinal cord, where are the arm fibers located in the lateral corticospinal tract relative to the leg fibers?
In the spinal cord, where are the arm fibers located in the lateral corticospinal tract relative to the leg fibers?
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Where are the corticospinal tracts located within the midbrain?
Where are the corticospinal tracts located within the midbrain?
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Which of the following describes the function of the direct activation pathways?
Which of the following describes the function of the direct activation pathways?
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A tumor pressing from outside the spinal cord would likely result in which of the following?
A tumor pressing from outside the spinal cord would likely result in which of the following?
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Which term describes severe paralysis affecting all four limbs?
Which term describes severe paralysis affecting all four limbs?
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Where do lower motor neurons that control arm and leg movements originate?
Where do lower motor neurons that control arm and leg movements originate?
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A patient experiences weakness on the right side of their body. Which term best describes this condition?
A patient experiences weakness on the right side of their body. Which term best describes this condition?
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A lesion to which structure would NOT result in real muscle weakness?
A lesion to which structure would NOT result in real muscle weakness?
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What is 'paresis' defined as in the text?
What is 'paresis' defined as in the text?
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Where do the upper motor neurons originate?
Where do the upper motor neurons originate?
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Which of the following is a common symptom associated with weakness?
Which of the following is a common symptom associated with weakness?
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Which of the following best describes 'plegia'?
Which of the following best describes 'plegia'?
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What is the correct term for severe paralysis of the legs?
What is the correct term for severe paralysis of the legs?
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Which of the following is NOT a location where motor fibers can be injured resulting in weakness?
Which of the following is NOT a location where motor fibers can be injured resulting in weakness?
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What type of muscle weakness is associated with neuromuscular junction disorders?
What type of muscle weakness is associated with neuromuscular junction disorders?
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A lesion in the motor cortex will cause paralysis on which side of the body?
A lesion in the motor cortex will cause paralysis on which side of the body?
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According to Table 4, what is the consequence of a small lacunar infarct on the face?
According to Table 4, what is the consequence of a small lacunar infarct on the face?
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Based on Table 4, what effects does a Middle Cerebral Artery (MCA) infarct have on the arm?
Based on Table 4, what effects does a Middle Cerebral Artery (MCA) infarct have on the arm?
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According to Table 4, what is the impact of a small lacunar infarct on the leg?
According to Table 4, what is the impact of a small lacunar infarct on the leg?
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According to Table 4, what is the impact of a Middle Cerebral Artery (MCA) infarct on the face?
According to Table 4, what is the impact of a Middle Cerebral Artery (MCA) infarct on the face?
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What type of paralysis is typically associated with a corticospinal tract lesion?
What type of paralysis is typically associated with a corticospinal tract lesion?
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According to Table 4, what is the severity of leg paralysis caused by a Middle Cerebral Artery (MCA) infarct?
According to Table 4, what is the severity of leg paralysis caused by a Middle Cerebral Artery (MCA) infarct?
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How many decussations are present in the dentato-thalamo-cortical and dentato-rubro-thalamo-cortical tracts?
How many decussations are present in the dentato-thalamo-cortical and dentato-rubro-thalamo-cortical tracts?
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Which side of the body does the cerebellum control, given the two decussations in the dentato-thalamo-cortical and dentato-rubro-thalamo-cortical tracts?
Which side of the body does the cerebellum control, given the two decussations in the dentato-thalamo-cortical and dentato-rubro-thalamo-cortical tracts?
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An infarct in the anterior cerebral artery (ACA) typically presents with which of the following clinical signs with respect to weakness?
An infarct in the anterior cerebral artery (ACA) typically presents with which of the following clinical signs with respect to weakness?
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A lesion in the internal capsule typically results in which of the following clinical signs?
A lesion in the internal capsule typically results in which of the following clinical signs?
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In a brainstem lesion resulting in crossed signs, which of the following combination of findings would be most likely?
In a brainstem lesion resulting in crossed signs, which of the following combination of findings would be most likely?
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What type of facial weakness accompanies a lesion in the facial nerve?
What type of facial weakness accompanies a lesion in the facial nerve?
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A patient presents with right arm spastic paralysis and right leg spastic paralysis. Where is the most likely location of the lesion, given these findings?
A patient presents with right arm spastic paralysis and right leg spastic paralysis. Where is the most likely location of the lesion, given these findings?
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What are the expected motor findings in both arms and legs in a transverse myelopathy of the entire upper cervical cord?
What are the expected motor findings in both arms and legs in a transverse myelopathy of the entire upper cervical cord?
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A patient presents with right arm flaccid paralysis and right leg spastic paralysis. Where is the likely location of the lesion?
A patient presents with right arm flaccid paralysis and right leg spastic paralysis. Where is the likely location of the lesion?
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A patient exhibits right arm flaccid paralysis and no leg weakness. Where is the most likely site of injury?
A patient exhibits right arm flaccid paralysis and no leg weakness. Where is the most likely site of injury?
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A patient has right leg spastic paralysis, but no arm weakness. Where is the most likely location of the lesion?
A patient has right leg spastic paralysis, but no arm weakness. Where is the most likely location of the lesion?
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What are the expected lower extremity findings in a transverse myelopathy of the entire thoracic spinal cord?
What are the expected lower extremity findings in a transverse myelopathy of the entire thoracic spinal cord?
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Which type of paralysis will be observed with a lesion of the lumbar spinal cord on one side?
Which type of paralysis will be observed with a lesion of the lumbar spinal cord on one side?
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What is characteristic about lumbar root or plexus lesions?
What is characteristic about lumbar root or plexus lesions?
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In the provided context, what is the primary difference in the presentation of an upper cervical spinal cord lesion compared to a lumbar spinal cord lesion?
In the provided context, what is the primary difference in the presentation of an upper cervical spinal cord lesion compared to a lumbar spinal cord lesion?
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Study Notes
Motor System Overview
- The motor system coordinates movement, planning, and execution.
- Ataxia describes uncoordinated movements.
- Muscle paralysis or weakness results from damage to the upper or lower motor systems.
Motor Neuron System
- Movement requires two interacting neuronal systems:
- Upper Motor Neuron (UMN): Originates in the cerebral cortex. Synapses with the lower motor neuron.
- Lower Motor Neuron (LMN): Originates in the brainstem (facial muscles) or ventral/anterior horn of the spinal cord (arms/legs).
- Damage to either system affects movement.
Paralysis and Weakness
- Paralysis is the loss of voluntary movement.
- Plegia: Severe paralysis (muscle strength 0-1/5).
- Hemiplegia: One side of the body.
- Quadriplegia: All four extremities.
- Paraplegia: Legs.
- Paresis: Lesser degree of paralysis (muscle strength 2-4/5).
- Hemiparesis: One side of the body.
- Plegia: Severe paralysis (muscle strength 0-1/5).
- Weakness: A variety of causes including body malaise, lack of motivation, depression, incoordination, rigidity, and true muscle weakness (motor fibers damaged).
Motor Pathways
- Direct activation pathways:
- Corticospinal tract: Initiates and controls voluntary, skilled activity.
- 90% decussate (cross over) at the medulla → lateral corticospinal tracts.
- 10% do not decussate → anterior corticospinal tracts.
- Corticobulbar tract: Controls cranial nerves (e.g., III, IV, VI, V, VII, IX, X, XI, XII) for facial and other movements.
- Corticospinal tract: Initiates and controls voluntary, skilled activity.
- Indirect activation pathways: Includes reticulospinal, vestibulospinal, rubrospinal, and tectospinal tracts.
- These pathways are involved in postural control, reflexive reactions and coordination.
Neurotransmitters
- Glutamate: Neurotransmitter at UMN-LMN synapse, within the brainstem (corticobulbar) and spinal cord (corticospinal)
- Acetylcholine: Neurotransmitter at neuromuscular junction.
Vascular Supply of the Motor System
- Middle Cerebral Artery (MCA): Supplies areas for face, arm, and hand control; occlusion leads to contralateral weakness affecting face and arm more than leg.
- Anterior Cerebral Artery (ACA): Supplies areas for leg control; occlusion leads to contralateral weakness affecting leg more than arm.
Primary Motor Cortex
- Located in the precentral gyrus (frontal lobe, Brodmann area 4).
- Dedicated areas for face, tongue, and hand movements due to their complex functions.
- Major source of upper motor neurons.
Corticospinal and Corticobulbar Tracts
- Corticospinal tract ends in the spinal cord.
- Corticobulbar tract ends in the brainstem (cranial nerves).
Upper vs. Lower Motor Neuron Paralysis
- Upper Motor Neuron (UMN) lesions: Spasticity, hyperreflexia, Babinski sign (extensor plantar response), atrophy.
- Lower Motor Neuron (LMN) lesions: Flaccidity, hypotonia, loss of reflexes, fasciculations, fibrillations, atrophy.
Reflexes
- Reflexes are the simplest motor coordination, using afferent and efferent arcs.
- Stretch reflex (e.g., knee-jerk reflex) is a monosynaptic reflex that occurs at the spinal cord level.
- Affected by damage to upper motor neurons or lower motor neurons.
Cerebellar System
- The cerebellum coordinates movement.
- Cerebellar damage causes ataxia (incoordination) ipsilateral to the lesion.
- Does not cause muscle weakness.
Localization of Lesions
- Lesion location in the brain, brainstem, or spinal cord determines the specific muscle group weakness, affecting either upper limbs or lower limbs first.
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Description
Test your knowledge on the reflex responses associated with lower and upper motor neuron lesions. This quiz covers key concepts related to muscle strength, paralysis types, and cerebellar lesions. Assess your understanding of the nervous system and its implications on reflexes and motor control.