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CNS: Anatomy# Motor Pathways
1. All of the following regarding muscle spindles are correct EXCEPT:
They are composed of intrafusal muscle fibers
They detect changes in muscle length and rate of stretch
They are innervated by alpha motor neurons
They act as checkpoints for muscle contractility
Explanation:
Muscle spindles are innervated by gamma motor neurons, not alpha motor neurons.
2. All of the following statements regarding muscle tone are true EXCEPT:
It represents baseline involuntary contraction
It is produced by continuous contraction of all sarcomeres
It helps maintain posture
It contributes to venous return
Explanation:
Muscle tone involves contraction of only a few sarcomeres.
3. All of the following are features of indirect (extrapyramidal) motor pathways EXCEPT:
They originate from the brainstem
They regulate posture and muscle tone
They include rubrospinal and vestibulospinal tracts
They directly regulate conscious voluntary movements
Explanation:
Conscious voluntary movement is controlled by direct (pyramidal) pathways.
4. Regarding the 2nd order neuron in motor pathways, all are correct EXCEPT:
Its axon exits via the anterior root
It is a local circuit interneuron
Its cell body lies in the anterior gray horn
It synapses with the lower motor neuron
Explanation:
Only lower motor neuron axons exit via the anterior root.
5. All of the following structures are traversed by corticospinal fibers EXCEPT:
Corona radiata
Posterior limb of internal capsule
Crus cerebri
Inferior cerebellar peduncle
Explanation:
Corticospinal fibers do not pass through cerebellar peduncles.
6. All of the following regarding the anterior corticospinal tract are correct EXCEPT:
It descends uncrossed initially
It is present throughout all spinal cord segments
It crosses at the spinal level
It controls neck and upper thoracic muscles
Explanation:
Anterior corticospinal tract is limited to cervical and upper thoracic levels.
7. All of the following correctly describe the rubrospinal tract EXCEPT:
Originates from the red nucleus
Decussates near its origin
Facilitates extensor muscle activity
Controls upper limb movements
Explanation:
Rubrospinal tract facilitates flexor muscles.
8. All of the following are true about the lateral vestibulospinal tract EXCEPT:
Originates from Deiter’s nucleus
Descends contralaterally in the lateral column
Facilitates extensor muscles
Controls anti-gravity muscles
Explanation:
Lateral vestibulospinal tract descends ipsilaterally.
9. All of the following are features of corticospinal tract lesions EXCEPT:
Early muscle atrophy
Loss of fine skilled movements
Absent abdominal reflexes
Positive Babinski sign
Explanation:
Muscle atrophy is minimal in UMN lesions.
10. The Babinski sign is normally present in infants because:
Corticospinal tract is hyperactive
Spinal reflexes are absent
Gamma neurons are immature
Corticospinal tract is not myelinated
Explanation:
Lack of myelination explains Babinski in infants.
11. All of the following are signs of extrapyramidal tract lesions EXCEPT:
Clonus
Clasp-knife rigidity
Severe muscle atrophy
Hyperreflexia
Explanation:
Severe atrophy is a LMN feature.
12. All are features of LMN lesions EXCEPT:
Hyperreflexia
Flaccid paralysis
Muscle fasciculations
Muscle atrophy
Explanation:
Hyperreflexia is a UMN sign.
13. All of the following cranial motor nuclei receive bilateral corticobulbar input EXCEPT:
Upper facial nucleus
Lower facial nucleus
Motor nucleus of trigeminal nerve
Nucleus ambiguus
Explanation:
Lower facial nucleus receives contralateral input.
14. A unilateral corticobulbar lesion causes all EXCEPT:
Contralateral lower facial weakness
Forehead sparing
Contralateral genioglossus weakness
Ipsilateral complete facial paralysis
Explanation:
Complete facial paralysis is LMN facial nerve lesion.
15. All of the following occur in hypoglossal LMN lesions EXCEPT:
Contralateral tongue deviation
Ipsilateral weakness
Tongue atrophy
Deviation toward lesion
Explanation:
LMN lesions cause tongue deviation toward lesion.
16. Paralysis of both lower limbs is termed:
Diplegia
Quadriplegia
Paraplegia
Hemiplegia
Explanation:
Paraplegia = paralysis of both lower limbs.
17. All of the following are features of internal capsule lesions EXCEPT:
Severe hemiplegia
Ipsilateral facial weakness
Upper and lower limb involvement
Contralateral paralysis
Explanation:
Internal capsule lesions cause contralateral deficits.
18. Alternative hemiplegia is best explained by a lesion in the:
Cerebral cortex
Internal capsule
Spinal cord
Brainstem
Explanation:
Brainstem lesions produce crossed findings.
19. All of the following regarding the motor homunculus are correct EXCEPT:
Equal cortical representation of all body parts
Large representation of hands and face
Located in precentral gyrus
Reflects motor complexity
Explanation:
Motor homunculus is disproportionate.
20. All are features of spinal shock EXCEPT:
Loss of reflexes below lesion
Loss of motor and sensory functions
Temporary condition
Permanent LMN destruction
Explanation:
Spinal shock is temporary and due to loss of supraspinal input.