Motor Control I Flashcards
what are the 3 different levels of motor control functional hierarchy?
Strategy – the goal and the movement strategy to best achieve this goal
Tactics – the sequence of spatiotemporal muscle contractions to achieve a goal smoothly and accurately
Execution – activation of motor neuron and interneuron pools to generate goal-directed movement
what structures are part of the function strategy?
Association neocortex, basal ganglion
what structures are part of the function tactics?
Motor cortex, cerebellum
what structures are part of the function execution?
Brain stem, spinal cord
what do the lateral pathways of the spinal cord control?
voluntary movements of distal muscles – under direct cortical control
what do ventromedial pathways of the spinal cord control?
posture and locomotion – under brain stem control
what is the important/longest lateral pathway?
Cortocospinal tract (CST)
where does the CST originate from?
areas 4 and 6 of frontal motor cortex – rest is somatosensory
where does the CST decussate(cross over)?
at medulla/spinal cord junction
what is the smaller lateral pathway?
rubrospinal tract (RST)
where does the RST start in?
red nucleus of midbrain – inputs from same cortical areas as CST
what occurs if there is a lesion of CST and RST?
fine movements of arms and hands lost. Can’t move shoulders, elbows, wrist and fingers independently.
what occurs if there is a lesion of CST alone?
same deficits, but after few months functions reappear. Been taken over by RST
what two ventromedial pathways control posture and locomotion?
Vestibulospinal(VST) and Tectospinal(TST) tracts
what is the role of VST & TST?
VST stabilizes head and neck
TST ensures eyes remain stable as body moves
what two ventromedial pathways control trunk and antigravity muscles?
Pontine and medullary reticulospinal tracts
where does the VST & TST originate?
VST-vestibular nucleus
TST-superior colliculus
where does the Pontine and medullary reticulospinal tracts originate?
pons + medulla
brainstem
describe the role of the Pontine and medullary reticulospinal tracts?
Use sensory information about balance, body position and vision
Reflexly maintain balance and body position
what occurs when the motor cortex directly activates spinal motoneurons?
frees them from reflex control by communicating via nuclei of ventromedial pathways
describe the Lower motor neurone distribution
somatotopic-
Medial ones control axial and proximal limb muscles, lateral ones innervate distal limb muscles
where does the mosaic of premotor areas lie?
anterior to primary motor cortex
what does the Somatotopic organisation of primary motor cortex mean?
point-for-point correspondence of an area of the body to a specific point on the primary motor cortex
what are the two somatotopically organised motor maps in area 6?
premotor area - PMA and supplementary motor area - SMA
what do the SMA & PMA innervate?
SMA innervates distal motor units directly
PMA connects reticulospinal neurones innervating proximal motor units
what can microstimulation in a specific area of the primary motor cortex elicit?
see movements that bring hands to mouth, or into central space, to inspect, or to manipulate, or to defend.
where in the brain are decisions taken about what actions/movements to take and their likely outcome?
prefrontal and parietal cortex
what parts of the brain generate the mental image of body in space?
somatosensory, proprioceptive and visual inputs to posterior parietal cortex (areas 5 and 7)
where is the junction where signals encoding what actions are desired are converted into how the actions will be carried out?
area 6
what is area 4 for?
“doing the desired movement” by activating the neurones of the CST and RST
decision making neurones in cortical PMA fire when?
when movement is made and when movement is imagined ie before it occurs
they also fire when others make the same specific movement
