Motor Control I Flashcards
Motor Control is a functional hierarchy with 3 levels. what are the three levels?
high, middle and low
what is the function and structures involved in the high level?
Strategy Association neocortex, basal ganglion
what is the function and structures involved in the middle level?
Tactics
Motor cortex, cerebellum
what is the function and structures involved in the low level?
Execution
Brain stem, spinal cord
what does ‘strategy’ mean in regards to the function of the high level?
Strategy – the goal and the movement strategy to best achieve this goal
what does ‘tactics’ mean in regards to the function of the middle level?
Tactics – the sequence of spatiotemporal muscle contractions to achieve a goal smoothly and accurately
what does ‘execution’ mean in regards to the function of the low level?
Execution – activation of motor neuron and interneuron pools to generate goal-directed movement
what does the lateral pathways do?
control voluntary movements of distal muscles – under direct cortical control
what does the ventromedial pathways do?
control posture and locomotion - under brain stem control
what tract is involved in the lateral pathway?
Cortocospinal tract (CST) – hugely important - longest, amongst largest tracts (~1 million axons)
where does the CST originate from?
2/3 of CST originates in areas 4 and 6 of the frontal motor cortex – the rest is somatosensory
where and why does the CST decussates?
at medulla/spinal cord junction, the CST crosses over (decussates), so that –
the right motor cortex controls the left side and the left motor cortex controls the right side
where does the CST axons synapse?
ventral horn motor neurones and interneurones to control muscles voluntarily.
where does the rubrospinal tract start?
A much smaller rubrospinal tract (RST) starts in the red nucleus of midbrain and receives inputs from same cortical areas as the CST.
what does a Lesion to CST and RST cause?
- fine movements of arms and hands are lost. Can’t move shoulders, elbows, wrist and fingers independently.
what does a Lesion to CST alone cause?
– same deficits seen, but after a few months functions reappear.
where do Large pyramidal neurones in motor cortex project via
CST
function of large pyramidal neurones in motor cortex?
They monosynaptically excite pools of agonist motoneurones
True or false:
The same pyramidal neurones branch and via interneurons inhibit pools of antagonist motoneurones.
true
function of the vestibulospinal tract?
VST stabilizes head and neck
function of tectospinal tract?
TST ensures eyes remain stable as body moves
what is Pontine and medullary reticulospinal tracts?
Originate in brain stem
Use sensory information about balance, body position and vision
Reflexly maintain balance and body position
Innervate trunk and antigravity muscles in limbs
what do voluntary movements require?
inputs from motor cortex via lateral pathways
can motor cortex activate spinal motoneurons directly?
yes
function of the motor cortex
can activate spinal motoneurons directly
also free spinal neurones from reflex control - by interactions with the nuclei of the ventromedial pathways
what plans and controls precise voluntary movements?
Primary motor cortex and pre-motor areas
what do Upper motor neurons in cortex and brainstem target?
lower motor neurons in the spinal cord
Lower motor neurone distribution is…
somatotopic
what do medial white matter control?
axial and proximal limb muscles
what do lateral white matter control
innervate distal limb muscles
where are the axons from, involved in lateral white matter?
motor cortex
where are the axons from, involved in medial white matter?
brainstem
medial tracts from brainstem control…
posture balance and orienting mechanisms.
lateral tracts from cortex control…
precise skilled voluntary movements.
origin of upper motor neurons?
cerebral cortex
brainstem
destination of UMN’s
cerebral cortex to LMN’s in lateral ventral horn
brainstem to LMN’s in medial ventral horn
where is the primary motor cortex?
in the precentral gyrus
what does sytematic probing of area 4 cause?
primary motor cortex revealed somatotopic organisation of precentral gyrus
what does the supplementary motor area innervate?
distal motor units directly
what does the premotor area connect with?
reticulospinal neurones innervating proximal motor units
Microstimulation in specific area of primary motor cortex (area 4) elicits…
coordinated movements of hand and mouth or
(B) movements that bring hands into central space to inspect/manipulate objects.
mental image of body in space is generated by
somatosensory, proprioceptive and visual inputs to posterior parietal cortex (areas 5 and 7).
what happens at the prefrontal and parietal cortex?
where decisions are taken -
which actions/movements to take and their likely outcome
what are the functions of the axons that converge on area 6
- here signals encoding desired actions are converted into how to carry this out
