Control Lecture 6: Descending motor pathways Flashcards
Causes of lower motor neuron lesions?
Traumatic injury
Poliomyelitis
Symptoms of lower motor neuron lesions?
Muscle wastage Muscle weakness Hypotonia Absent reflexes Fasciculation/fibrillation
Functions of upper motor neurons?
Modify LMN activity
Modify reflexes
Coordinate complex movements
Where is the primary motor cortex in the brain?
Precentral gyrus
Initial symptoms of upper motor neuron lesions?
Paralysis of opposite limbs
Loss of reflexes
Symptoms of upper motor neuron lesions after a few weeks?
Reduced but partially recovered function
Hypertonia
Symptoms of upper motor neuron lesions in the long term?
Hyperreflexia
Spasticity
How is the precentral gyrus somatotopically organised from medial to lateral?
Legs Trunk Arms Face Tongue Throat
What is the function of the corticospinal tract?
Fine motor movements
Where does the corticospinal tract pass to from the precentral gyrus?
Internal capsule
Where in the internal capsule do descending fibres to the face pass through?
Genu
Where in the internal capsule do descending fibres to the body pass through?
Posterior limb
How is the posterior limb of the internal capsule somatotopically organised from anterior to posterior?
Arms
Trunk
Legs
Does the corticospinal tract pass along the ventral or dorsal side of the brainstem?
Ventral
What structures in the midbrain does the corticospinal tract pass through?
Cerebral peduncles
What structures in the medulla does the corticospinal tract pass through?
Pyramids
Where is the decussation of the corticospinal tract?
Pyraminds of the medulla
How is the corticospinal cord in the brainstem organised from lateral to medial?
Legs
Trunk
Arms
Face
Roughly what percentage of fibres in the corticospinal tract cross in the main decussation?
85%
Where do fibres travel in after the decussation in the pyramids?
Lateral corticospinal tract
Where do fibres that don’t decussate in the pyramids descend in the spinal cord?
Ventral corticospinal tract
Where do fibres in the corticospinal tracts enter the ventral grey horn?
At the spinal cord level where their rootlets exit
Is the ventral corticospinal tract contralateral or ipsilateral to the origins of the fibres in the brain?
Ipsilateral
Within what do fibres in the ventral corticospinal tract decussate?
Ventral white commissure
How is the lateral corticospinal tract somatotopically organised from anterior to posterior?
Arm
Trunk
Legs
What is the name of the descending motor pathway to the face?
Corticobulbar pathway
Which cranial nerves aren’t innervated bilaterally?
Facial (VII)
Hypoglossal (XI)
How is the hypoglossal nerve served?
Contralaterally
How is the upper face served by the facial nerve?
Bilaterally
How is the lower face served by the facial nerve?
Contralaterally
Would paralysis across half of the face characterise lower or upper motor neuron damage?
Lower
Would paralysis across a quarter of the face characterise lower or upper motor neuron damage?
Upper
