PHYSIOLOGY - UMNs and control of movement Flashcards
what is the essential feature for a simple spinal central pattern generator to command rhythmic alternating activity that moves a limb
an excitatory interneurone to display oscillatory or pacemaker activity
what are the 3 levels of motor control
high middle and low
what is forms the highest level of motor control
neocortical association areas and basal ganglia
- strategy
what forms the middle tier of motor control
motor cortex and cerebellum
- tactics
what forms the lowest tier of motor control
brain stem and spinal cord
- execution
what are the 2 pathways of the descending tracts
lateral and ventromedial pathways
the lateral pathways are under control of from the
cerebral cortex
the ventromedial pathways are under the control from the
brainstem
what is brown sequard syndrome
hemisection of the cord
- ipsilateral paralysis
- ipsilateral hyperreflexia and extensor plantar reflex
- ipsilateral loss of DCML
- contralateral loss of spinothalamic
what is the major lateral pathway
corticospinal tract
why is the corticospinal tract considered pyramidal
passes through the medullary pyramids
where are the cell bodies of the corticospinal tract located
BA4 and BA6 of motor cortex and somatosensory areas of the parietal cortex
where do axons of the corticospinal tract course from the cortex
descend through internal capsule to base of medulla
pass through crus cerebri of the midbrain, pons and medulla
where do fibres of the corticospinal tract decussate
most decussate in the caudal medulla (pyramidal decussation) to form the lateral corticospinal tract
remainder stay ipsilateral to form ventral corticospinal tract and decussate segmentally more caudally
after fibres of the lateral corticospinal tract decussate where do they go and terminate
descend into the spinal cord terminating in the dorsolateral region of the ventral horn at all segmental levels
where do fibres of the ventral corticospinal tract go once they have decussated
decussate and terminate in the ventral horn of the cervical and upper thoracic segmental levels
what does the corticospinal tract control
supplies muscles of body - fine precise movements particularly of distal musculature
what is found in the dorsolateral region of the ventral horn and intermediate grey
location of LMNs and interneurons controlling distal muscles
true/false
the left side of the brain always control right side musculature
true
what are the 2 pyramidal tracts and their functions
corticospinal tract - supples muscles of body
corticobulbar tract - supplies muscles of head and neck
pyramidal tracts are responsible for voluntary/involuntary movements
voluntary
extra-pyramidal tracts originate where
brainstem
extra-pyramidal tracts control what
involuntary and automatic control of all musculature such as muscle tone balance posture and locomotion
what is the internal capsule
white matter pathway located between the thalamus and the basal ganglia
what is capsular stroke
internal capsule is particularly susceptible to compression from haemorrhagic bleeds
where does the corticobulbar tract arise from
lateral motor cortex
where do neurones of the corticobulbar tract terminate
motor nuclei of the cranial nerves where they synapse with LMNs which carry motor signals to muscles of face and neck
true/false
both right and left fibres of the corticobulbar tract innervate the motor neurones bilaterally
true
what are the 2 exceptions to the bilateral innervation of the corticobulbar tract
UMNs for the facial nerve only have contralateral innervation of muscles below the eyes
UMNs for the hypoglossal nerve only provide contralateral innervation
name a minor lateral pathway other than the corticospinal or corticobulbar
rubrospinal
is the rubrospinal tract pyramidal or extrapyramidal
extrapyramidal
cell bodies of the rubrospinal tract are found where
red nucleus
the red nucleus receives input from where
motor cortex and cerebellum
axons of the rubrospinal tract decussate where
ventral tegmental decussation in the midbrain
axons of the rubrospinal tract descend the spinal cord where in relation to the lateral corticospinal tract
ventrolateral
where do axons of the rubrospinal tract terminate
ventral horn
the rubrospinal tract exerts control over what muscles
flexors
true / false
if the corticospinal tract is damaged the rubrospinal tract can compensate to a good degree
true
what controls fine movements of hand
rubrospinal tract
give 2 things lesions of the lateral columns is associated with
- cant move shoulders/elbow/wrist/fingers independently
- slowing and impairment of accuracy of voluntary movements
would a lesion of the lateral column have much effect on normal posture
no
what are the 3 ventromedial pathways
vestibulospinal
tectospinal
reticulospinal
what are the 2 vestibulospinal pathways
medial and lateral
where does the vestibulospinal tract arise
lateral and medial vestibular nuclei
what do the vestibular nuclei receive input from
CN VIII - vestibulocochlear nerve which gets info from vestibular labyrinths
does the vestibulospinal tract decussate
no - descends spinal cord and remains ipsilateral
where is the lateral vestibular nucleus (Deiter’s nucleus)
pons
where is the medial vestibular nucleus
medulla
input from where is also important for the vestibulospinal tract
cerebellum
how far down does the lateral vestibulospinal tract descend
until the lumbar spinal cord
what does the LVST control
helps to hold upright and balanced posture - extensor MNs of antigravity muscles e.g. of the leg
how dar down does the medial VST descend
cervical spinal cord
what does the MVST control
cervical spinal circuits that control neck and back muscles guiding the head
which of the tracts of the VST is longer
lateral is longer - goes from higher up to further down
where do cell bodies of the tectospinal tract originate
superior colliculus of the midbrain
the superior colliculus receives input from what
retina (optic nerves)
visual cortex
afferents conveying somatosensory and auditory information
where do axons of the tectospinal tract decussate
dorsal tegmental decussation of the midbrain
axons of the tectospinal tract descend the spinal cord close to the midline and go to what
cervical spinal cord influencing muscles of the neck upper trunk and shoulders
what does the tectospinal tract do in general
coordinates movement of the head and eyes in relation to visual stimuli
what are the 2 reticulospinal tracts
medial (pontine)
lateral (medullary)
where does the MRST arise
pons
where does the LRST arise
medulla
what does the MRST control
voluntary movements and increases muscle tone
enhances anti-gravity reflexes of the spinal cord
helps to maintain standing posture by facilitating contraction of the extensors of lower limbs
what does the LRST control
opposes the action of the medial tract - releases antigravity muscles from reflex control
which of the RST descends ipsilaterally and which descends bilaterally
medial - ipsilaterally
lateral - bilaterally
what are the cardinal signs of an UMN of corticospinal tract
hypertonia hyperreflexia clonus babinski sign muscle weakness
why does damage to the corticobulbar tract usually result in mild muscle weakness
bilateral innervation of majority from corticobulbar tract
lesion to the UMNs of the corticobulbar supply of CN VII would result in
spastic paralysis of the muscles in the contralateral lower face
lesion to UMNs of corticobulbar supply of CN XII would result in
spastic paralysis of contralateral genioglossus - deviation of tongue to contralateral side
decorticate posture: (flexor/extensor) position
flexor
FLEX my new DECOR
what are the hands like in decorticate
in decortiCate
hands are like Cs and move toward the Cord (midline)
decorticate posture occurs due to problem with
cervical spinal tract or cerebral hemisphere
decerebrate posture: (flexor/extensor) position
extensor
dEcErEbratE
the arms are like what in decerebrate posture
like e’s
and down to sides
decerebrate posture is due to a problem with what
midbrain or pons
