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
