Motor Neuron Quiz

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Motor Neuron Quiz - Quiz

Are you an expert in motor neurology? Test yourself right now with this motor neuron quiz here. Motor neurons are meant by a specialized type of brain cell called neurons, located within the spinal cord and the brain. There are two main subtypes. These two types are the upper motor neurons and the lower motor neurons. Here are some questions for your practice and a better understanding of motor neurology. Give your best shot!


Questions and Answers
  • 1. 

    A 74-year-old woman was residing in a rehabilitation facility while recovering from an infection. She was doing well until one morning. She suddenly developed slurred speech and right-sided weakness. An emergency neurologist was consulted. Her medical history was notable for hypertension, coronary artery disease, and a recent onset of atrial fibrillation. Examination revealed weak movements of the right face with only mild forehead involvement. Decreased palate movement on the right and rightward tongue deviation. The neurologist suspected lacunar infarction, which was confirmed by MRI. Where is the possible localization?

    • A.

      Left prefrontal gyrus medial part of the hemisphere

    • B.

      Right Broca area with involvement of lower part of Brodmann area 4.

    • C.

      Left posterior limb of the internal capsule

    • D.

      Left genu of the internal capsule

    • E.

      Right posterior limb and genu of the internal capsule

    Correct Answer
    D. Left genu of the internal capsule
    Explanation
    The patient's symptoms of slurred speech and right-sided weakness are consistent with a lacunar infarction, which is a small stroke caused by blockage of a small blood vessel in the brain. The specific localization of the infarction is suggested to be in the left genu of the internal capsule. The internal capsule is a white matter tract that contains fibers responsible for motor function. Damage to the left genu of the internal capsule can result in weakness on the opposite side of the body, which is consistent with the patient's right-sided weakness.

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  • 2. 

    Your elderly neighbor has difficulties in picking up his newspaper properly from his porch, and you have also noticed that he exhibits issues with correctly grasping his brandy glass when he invites you over for a drink. He told you that he has problems controlling the distance of his movements. You know this to be which of the following?

    • A.

      Akinesia

    • B.

      Dysdiadochokinesia

    • C.

      Bradykinesia

    • D.

      Dysphagia

    • E.

      Dysmetria

    Correct Answer
    E. Dysmetria
    Explanation
    Dysmetria is the correct answer because it refers to the difficulty in controlling the distance, direction, and speed of movements. This can result in overshooting or undershooting a target, as seen in the example of the elderly neighbor struggling to pick up the newspaper and grasp the brandy glass accurately. Akinesia refers to the absence or reduction of voluntary muscle movements, dysdiadochokinesia refers to the inability to perform rapid alternating movements, bradykinesia refers to slowness of movement, and dysphagia refers to difficulty in swallowing.

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  • 3. 

    A 52-year-old woman who is unable to move her left leg visits your office. Sensory modalities in all of her limbs are retained and there appears to be no sign of weakness in any of her other limbs. In which of the following structures are the cell bodies of lower motor neurons innervating the lower limb located?

    • A.

      Lamina I-VI

    • B.

      Lamina VIII, IX

    • C.

      Lamina X

    • D.

      Lamina I, II

    • E.

      Lamina III, IV

    Correct Answer
    B. Lamina VIII, IX
    Explanation
    The cell bodies of lower motor neurons innervating the lower limb are located in Lamina VIII, IX. This is indicated by the fact that the patient is unable to move her left leg, suggesting a problem with the lower motor neurons responsible for controlling movement in that limb. The sensory modalities in all of her limbs are retained, indicating that the issue is specific to the motor neurons and not the sensory neurons. Additionally, there is no sign of weakness in her other limbs, further supporting the idea that the problem is localized to the lower limb.

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  • 4. 

    A 24-year-old woman is rushed to the hospital following severe head injuries. She is displaying a specific rigidity that is a result of lesions rostral to the red nucleus. What symptoms is she displaying?

    • A.

      Lower extremity weakness

    • B.

      Weakness of the masticatory muscles

    • C.

      Upper and lower limb extension

    • D.

      Upper limb flexion and lower limb extension

    • E.

      Deviation of the tongue on the protrusion

    Correct Answer
    D. Upper limb flexion and lower limb extension
    Explanation
    The woman is displaying upper limb flexion and lower limb extension. Lesions rostral to the red nucleus can result in decerebrate rigidity, which is characterized by stiff extension of the upper limbs and extension of the lower limbs. This is due to disruption of the descending pathways that normally inhibit the extensor muscles and facilitate flexor muscles.

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  • 5. 

    A 34-year-old man is rushed to the emergency room from the site of a car accident. An MRI reveals a lesion at the level of the midbrain. His upper and lower limbs are extended. Name (i) the type of rigidity and (ii) the tract/tracts involved in the extension of the limbs.

    • A.

      Decorticate; Rubrospinal tract

    • B.

      Decorticate; Medial reticulospinal and lateral vestibulospinal tract

    • C.

      Decerebrate; Rubrospinal and lateral vestibulospinal tract

    • D.

      Decerebrate; Rubrospinal tract

    • E.

      Decerebrate; Medial reticulospinal and lateral vestibulospinal tract

    Correct Answer
    E. Decerebrate; Medial reticulospinal and lateral vestibulospinal tract
    Explanation
    The correct answer is "Decerebrate; Medial reticulospinal and lateral vestibulospinal tract". Decerebrate rigidity is characterized by extension of the upper and lower limbs. It is caused by damage to the brainstem, specifically the midbrain. In decerebrate rigidity, the lesion affects the rubrospinal tract, which is responsible for flexor tone, as well as the medial reticulospinal and lateral vestibulospinal tracts, which are responsible for extensor tone. This leads to unopposed extensor tone in the limbs, resulting in the characteristic rigid extension seen in decerebrate rigidity.

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  • 6. 

    A 22-year-old woman n is suffering from bilateral weakness of her lower limbs. Which of the following represents the most likely location of this lesion?

    • A.

      A lesion rostral to the pyramidal decussation

    • B.

      The left genu of the internal capsule

    • C.

      The right posterior limb of the internal capsule

    • D.

      A lesion caudal to the pyramidal decussation

    • E.

      The right genu of the internal capsule

    Correct Answer
    D. A lesion caudal to the pyramidal decussation
    Explanation
    The pyramidal decussation is the point at which the fibers of the corticospinal tract cross over from one side of the brain to the opposite side of the spinal cord. Bilateral weakness of the lower limbs suggests a lesion affecting both sides of the corticospinal tract. Since the lesion is caudal to the pyramidal decussation, it is likely affecting the fibers after they have crossed over, leading to weakness in both lower limbs.

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  • 7. 

    Which of the following represents the fibers that fan out from the internal capsule into the white matter of the hemisphere?

    • A.

      Cingulum

    • B.

      Corona Radiata

    • C.

      Genu of the corpus callosum

    • D.

      Superior longitudinal fasciculus

    • E.

      Uncinate fasciculus

    Correct Answer
    B. Corona Radiata
    Explanation
    The fibers that fan out from the internal capsule into the white matter of the hemisphere are represented by the Corona Radiata.

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  • 8. 

    Damage to the efferent portion of the muscle spindle would involve which of the following fiber types?

    • A.

      B fibers

    • B.

      Aa fibers

    • C.

      C fibers

    • D.

      Ay fibers

    • E.

      AB fibers

    Correct Answer
    D. Ay fibers
    Explanation
    Damage to the efferent portion of the muscle spindle would involve Ay fibers. The muscle spindle is responsible for providing proprioceptive information about muscle length and tension. The efferent fibers of the muscle spindle, specifically the Ay fibers, transmit signals from the central nervous system to the muscle spindle, allowing for modulation of its sensitivity and function. Therefore, damage to the efferent portion of the muscle spindle would affect the Ay fibers.

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  • 9. 

    A 54-year-old morbidly obese and hypertensive man is brought to the emergency department after experiencing the sudden onset of weakness in his left upper and lower extremities. CT shows an infarcted area in the medulla. Damage to which of the following tracts or fiber bundles of the medulla would most likely explain this deficit?

    • A.

      Anterolateral system

    • B.

      Corticospinal fibers

    • C.

      Medial Lemniscus

    • D.

      Rubrospinal tract

    • E.

      Vestibulospinal fibers

    Correct Answer
    B. Corticospinal fibers
    Explanation
    Damage to the corticospinal fibers in the medulla would most likely explain the sudden onset of weakness in the left upper and lower extremities. The corticospinal tract is responsible for voluntary motor control, and it carries signals from the motor cortex to the spinal cord. Damage to this tract would result in a loss of motor function on the opposite side of the body, as the fibers decussate (cross over) in the medulla. Therefore, in this case, the weakness in the left upper and lower extremities is likely due to damage to the corticospinal fibers on the right side of the medulla.

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  • 10. 

    A 23-year-old man is brought to the emergency room from the site of an automobile collision. The neurological examination reveals weakness of the right lower extremity and a loss of pain and thermal sensations on the left side, beginning at the level of the umbilicus. CT shows a fracture of the vertebral column with the displacement of bone fragments into the vertebral canal. Damage to which of the following tracts would correlate with weakness of the lower extremity in this man?

    • A.

      Left lateral corticospinal tract

    • B.

      Reticulospinal fibers on the right

    • C.

      Right lateral corticospinal tract

    • D.

      Right rubrospinal tract

    • E.

      Vestibulospinal fibers on the right

    Correct Answer
    C. Right lateral corticospinal tract
    Explanation
    The given scenario describes a patient with weakness of the right lower extremity and loss of pain and thermal sensations on the left side starting at the level of the umbilicus. This pattern of symptoms suggests a lesion on the right side of the spinal cord. The lateral corticospinal tract is responsible for motor control of the contralateral side of the body, meaning that damage to the right lateral corticospinal tract would result in weakness of the right lower extremity. Therefore, the weakness in this man is likely due to damage to the right lateral corticospinal tract.

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  • 11. 

    Which of the following represents the most likely level of damage to the spinal cord resulting from the fracture to the vertebral column in this man?

    • A.

      T6 on the left

    • B.

      T8 on the left

    • C.

      T8 on the right

    • D.

      T10 on the left

    • E.

      T10 on the right

    Correct Answer
    C. T8 on the right
    Explanation
    Fracture to the vertebral column at the T8 level on the right side would most likely result in damage to the spinal cord at that level. The spinal cord is located within the vertebral column and is responsible for transmitting sensory and motor signals between the brain and the rest of the body. Damage to the spinal cord can lead to loss of sensation and motor function below the level of the injury. In this case, the fracture at T8 on the right side suggests that the spinal cord at that level is most likely affected, resulting in potential loss of function on the right side of the body below that level.

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  • 12. 

    Based on their relative locations in the spinal cord, which of the following tracts or fiber bundles would most likely be involved In a lesion located in the immediate vicinity of the lateral corticospinal tract?

    • A.

      Anterolateral system

    • B.

      Anterior spinocerebellar tract

    • C.

      Gracile fasciculus

    • D.

      Medial longitudinal fasciculus

    • E.

      Rubrospinal tract

    Correct Answer
    E. Rubrospinal tract
    Explanation
    A lesion located in the immediate vicinity of the lateral corticospinal tract would most likely involve the Rubrospinal tract. The Rubrospinal tract is located adjacent to the lateral corticospinal tract in the spinal cord. Both tracts are involved in motor function, with the lateral corticospinal tract primarily responsible for fine motor control and the Rubrospinal tract involved in controlling muscle tone and limb flexion. Therefore, a lesion in this area would likely affect motor function and muscle control.

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  • 13. 

    A 37-year-old man is brought to the emergency department with a severe head injury. Within a few hours, he is decerebrate (upper and lower extremities extended) and comatose. The extension of his extremities indicates a dominant input to extensor motor neurons through reticulospinal fibers/tracts. Which of the following most specifically describes the position of these activated fibers within the spinal cord?

    • A.

      Anterolateral area (area of anterolateral system)

    • B.

      Posterolateral area (area of lateral corticospinal tract)

    • C.

      Posteriorcolumns

    • D.

      Posterolateral (dorsolateraI)tract

    • E.

      Intermediate zone

    Correct Answer
    A. Anterolateral area (area of anterolateral system)
    Explanation
    The correct answer is Anterolateral area (area of anterolateral system). The extension of the patient's extremities indicates a dominant input to extensor motor neurons through reticulospinal fibers/tracts. The anterolateral area of the spinal cord is responsible for transmitting pain and temperature sensations, as well as controlling involuntary motor movements. In this case, the activation of the reticulospinal fibers in the anterolateral area is causing the extension of the patient's extremities.

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  • 14. 

    A 47-year-old man is transported to the emergency department from the site of an automobile collision. The examination reveals a paralysis of both lower extremities. Which of the following most specifically identifies this clinical picture?

    • A.

      Alternating hemiplegia

    • B.

      Hemiplegia

    • C.

      Monoplegia

    • D.

      Quadriplegia

    • E.

      Paraplegia

    Correct Answer
    E. Paraplegia
    Explanation
    Paraplegia is the most specific term that identifies the clinical picture described in the question. Paraplegia refers to paralysis of both lower extremities, which matches the examination findings of the 47-year-old man who was involved in an automobile collision. This term specifically indicates the loss of motor function in the lower limbs while the upper limbs remain unaffected. Alternating hemiplegia refers to episodes of paralysis that alternate between the left and right sides of the body, hemiplegia refers to paralysis on one side of the body, monoplegia refers to paralysis of a single limb, and quadriplegia refers to paralysis of all four limbs.

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  • 15. 

    A 57-year-old woman presents with the main complaint of difficulty speaking. The examination reveals that the woman's tongue deviates to the right on the attempted protrusion. When she says \\Ah," her soft palate elevates slightly on the left, and the uvula deviates to the same side. This combination of deficits most likely indicates a small lesion in which of the following?

    • A.

      Crus cerebri on the right

    • B.

      Genu of the internal capsule on the left

    • C.

      Genu of the internal capsule on the right

    • D.

      Lateral medulla on the right

    • E.

      Medial medulla on the right

    Correct Answer
    B. Genu of the internal capsule on the left
    Explanation
    The combination of difficulty speaking, deviation of the tongue to the right, and elevation of the soft palate and uvula to the left suggests a lesion in the left side of the brain. The genu of the internal capsule is a structure in the brain that contains motor fibers responsible for controlling movement of the tongue and soft palate. A lesion in the genu of the internal capsule on the left side would result in weakness or paralysis of the muscles on the right side of the body, including the tongue and soft palate, leading to the observed symptoms.

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  • 16. 

    A 70-year-old woman is brought to the emergency department by members of the volunteer fire department of a small town. She primarily complains of weakness. The examination reveals hemiplegia involving the left upper and lower extremities, sensory losses (pain, thermal sensations, and proprioception) on the left side of the body and face, and a visual deficit in both eyes. MRI shows an area of infarction consistent with the territory served by the anterior choroidal artery. The weakness of the extremities in this woman is most likely due to damage to which of the following?

    • A.

      Corticospinal fibers on the left

    • B.

      Corticospinal fibers on the right

    • C.

      Somatomotor cortex on the right

    • D.

      Thalamocortical fibers to the motor cortex on the right

    • E.

      Thalamocortical fibers to the sensory cortex on the right

    Correct Answer
    B. Corticospinal fibers on the right
    Explanation
    The patient's symptoms of weakness, sensory loss, and visual deficit on the left side of the body indicate a lesion on the right side of the brain. The anterior choroidal artery supplies blood to the internal capsule, which contains the corticospinal fibers responsible for motor control. Damage to the corticospinal fibers on the right side would result in weakness on the left side of the body, known as contralateral hemiplegia. Therefore, the weakness in this woman is most likely due to damage to the corticospinal fibers on the right side.

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  • 17. 

    A 57-year-old man presents with hoarseness. The neurological examination reveals a deviation of the uvula to the left on phonation, deviation of the tongue to the right on the protrusion, and weakness of the facial muscles around the mouth on the right. Which of the following would most likely also be seen in this man?

    • A.

      Inability to turn his head to the left against resistance

    • B.

      Inability to turn his head to the right against resistance

    • C.

      Inability to shrug the right shoulder against resistance

    • D.

      Weakness of the masticatory muscles on the left

    • E.

      Weakness of the masticatory muscles on the right

    Correct Answer
    A. Inability to turn his head to the left against resistance
    Explanation
    The given symptoms of deviation of the uvula to the left on phonation, deviation of the tongue to the right on the protrusion, and weakness of the facial muscles around the mouth on the right suggest a lesion in the left hypoglossal nerve (CN XII) and right facial nerve (CN VII). These cranial nerves are responsible for the movement of the tongue and facial muscles. Since the hypoglossal nerve also innervates the muscles responsible for turning the head to the opposite side, the most likely additional symptom would be an inability to turn his head to the left against resistance.

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  • 18. 

    A 57-year-old obese man is brought to the emergency department by his wife. The examination reveals that cranial nerve function is normal, but the man has bilateral weakness of his lower extremities. He has no sensory deficits. MRI shows a small infarcted area in the general region of the cervical spinal cord-medulla junction. Which of the following represents the most likely location of this lesion?

    • A.

      Caudal part of the pyramidal decussation

    • B.

      Lateral corticospinal tract on the left

    • C.

      Pyramids bilaterally

    • D.

      Pyramid on the right

    • E.

      Rostral part of the pyramidal decussation

    Correct Answer
    A. Caudal part of the pyramidal decussation
    Explanation
    The most likely location of the lesion in this case is the caudal part of the pyramidal decussation. This is because the patient has bilateral weakness of his lower extremities, indicating a problem with the corticospinal tract. The pyramidal decussation is where the corticospinal fibers cross over from one side of the brain to the opposite side of the spinal cord. Lesions in this area would result in bilateral weakness of the lower extremities, which matches the patient's symptoms. The other options do not explain the bilateral weakness seen in the patient.

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  • 19. 

    As a medical student, you are tapping the patellar tendon to activate the knee jerk reflex. The resulting reflex is within a normal range. Which sensory organ is activated in response to this stimulus?

    • A.

      Golgi tendon organ

    • B.

      Merkel cell

    • C.

      Pacinian corpuscle

    • D.

      Muscle spindle

    • E.

      Ruffini ending

    Correct Answer
    D. Muscle spindle
    Explanation
    When tapping the patellar tendon, the resulting knee jerk reflex is within a normal range. The sensory organ that is activated in response to this stimulus is the muscle spindle. The muscle spindle is a proprioceptor located within the muscle that detects changes in muscle length and rate of change, allowing for the body to maintain balance and coordination. In this case, the muscle spindle is activated by the stretch of the patellar tendon, leading to the reflexive contraction of the quadriceps muscle and extension of the leg.

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  • 20. 

    A 79~year old man is experiencing peripheral nerve damage to his lower right limb. Which of the following is characteristic of lower motor neuron damage?

    • A.

      Hyperreflexia

    • B.

      Increased tone

    • C.

      Hyporeflexia

    • D.

      Spastic paralysis

    • E.

      Increased muscle mass

    Correct Answer
    C. Hyporeflexia
    Explanation
    Hyporeflexia is characteristic of lower motor neuron damage. Lower motor neurons are responsible for transmitting signals from the spinal cord to the muscles, and damage to these neurons can result in decreased or absent reflexes. Hyperreflexia, increased tone, and spastic paralysis are more commonly associated with upper motor neuron damage. Increased muscle mass is not a characteristic of lower motor neuron damage.

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  • Current Version
  • Aug 26, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Jan 24, 2012
    Quiz Created by
    BLACKMD
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