9 Descending control of spinal circuits and the motor cortex Flashcards
What are the 2 key divisions of the descedning motor pathways?
lateral (somatic)
ventromedial (autonomic, brainstem)
Name 3 features of the motor system
Hierarchical organisation
Feedback loops
Somatotopic representation
What 3 structures does the cerebellum interact with?
brainstem
thalamus
spinal cord
What are the 3 basic types of movement?
reflex
rhythmic motor patterns
voluntary
What types of fibres are LMNs?
alpha-MN
What sorts of MN are not involved in reflexes?
UMN
What muscles tend to be innervated by ventromedial MNs?
axial muscles
proximal appendicular muscles
What muscles tend to be innervated by lateral MNs?
distal appendicular muscles
FINE MOTOR
What are the different lateral pathways?
direct to from motor cortex (corticospinal tract)
indirect via red nucleus (rubrospinal tract)
Where does the corticospinal tract decussate?
respective spinal level
What is the structure of the corticospinal tract?
monosynaptic contact with aMNs
majority of axons from neurons with cell bodies in the motor cortex (areas 4 and 6)
innervate aMNs controlling distal muscles (flexors mainly)
What is the structure of the Rubrospinal tract?
contralateral projections from red nucleus running down the latearl column of the spinal cord
Why might you severe latearl ascending spinal sensoyr pathways?
What do you need to watch out for?
to relieve intractable pain
don’t want to damage the lateral descending motor pathway
Why is there no impact on posture when you severe lateral ascending pathways?
you don’t damage the ventro-medial tracts
What happens in selective corticospinal tract lesions?
rubrospinal tract can compensate almost entriely for loss of corticospinal (not fine digit control tho)
re-routing of cortical output via rubrospinal tract
