Upper Motor Neuron Flashcards
Where are the cell bodies of UMN located?
Cerebral cortex or brain stem
What is an upper motor neuron?
A first order neuron in control of movement (efferent fibres)
Where in the spinal cord do UMN descending tracts synapse with the lower motor neurons?
Ventral horn of grey matter
What is the function of motor UMN from the cortex?
Initiating, maintaining, planning sequences of voluntary movements
What is the function of the UMN from the brain stem?
Regulation of muscle tone, control of posture and basic navigational movements
What are the two forms of movement?
Voluntary, conscious, skilled movement
Postural, antigravity muscle tone
What are the characteristics of voluntary, skilled movements?
Learned movements
Mediated mainly by flexor muscles
Discrete contraction of a few muscle groups distant to spinal cord (extremities)
What are the characteristics of postural, antigravity muscle tone?
Subconscious and involuntary
Mediated by extensor muscles
Contraction of larger groups located closer to spinal cord (trunk/proximal limb)
What is the role of the ventromedial UMN tracts?
Maintenance of balance and posture
What are the ventromedial UMN tracts?
Vestibulospinal tract
Reticulospinal tract
What is the function of the vestibulospinal tract?
Medial: adjusts head/neck position in response to changes in posture
Lateral: activate LMN of trunk and limbs to facilitate extensors (inhibit flexors)
What is the function of the medial vestibulospinal tract?
Adjusts head/neck position in response to changes in posture
What is the function of the medial vestibulospinal tract?
Activate LMN of trunk and limbs to facilitate extensors (inhibit flexors)
Also receives input from vestibular apparatus
Where does the vestibulospinal tract originate?
Vestibular nuclei
Describe the course of the lateral vestibulospinal tract?
Originates in vestibular nuclei
Descends ipsilaterally through the
Describe the course of the medial vestibulospinal tract?
Originates in vestibular nuclei
Descends bilaterally through the
What are the two reticulospinal tracts?
Medullary (lateral) and Pontine (medial)
What are the functions of the reticulospinal tract?
Coordinates axial and proximal limb muscles
Mediate autonomic activity
Pain modulation
Where does the reticulospinal tract originate?
Reticular formation (projections from cortex)
What is the function of the medullary reticulospinal tract?
Suppresses extensor spinal reflex activity
What is the function of the pontine reticulospinal tract?
Facilitates extensor spinal reflex activity
What is the function of the tectospinal tract?
Controls axial musculature of neck
Reflexive coordination of head and eye movements in response to visual/auditory stimuli
Where does the tectospinal tract originate?
Colliculi (superior) in visual tectum of midbrain
Where does the tectospinal tract project to?
Cervical and thoracic spinal cords
