Functional hierarchy of the motor system Flashcards
Motor control is a functional hierarchy with 3 levels:
+ name the parts of the brain/CNS associated with each level
High (strategy) - association areas, basal ganglia
Middle (tactics) - motor cortex, cerebellum
Low (execution) - brainstem, spinal cord
Alpha motorneurons are also known as what neurons
LMNs
4 components of the voluntary motor system
Descending control pathways
Basal ganglia
Cerebellum
Local spinal cord/brain stem circuits
There’s lots of … input to local circuit neurons (formed by LMNs)
sensory input
Spinal cord reverts descending input from… (2)
Brainstem AND cortical input via corticospinal tract
Sensory input enters at different levels and is crucial in each: (3)
Spinal cord - in the form of proprioceptors nociceptors etc
Brainstem - vestibular system informs about balance
Cortical level - we make movements in repsonse to visual, olfactory, auditory cues etc
Can descending inputs interact with segmental reflexes + if so, what are these descending inputs and how do they work
Yes
Brainstem nuclei can over-ride and exert control over spinal reflexes
What does it mean by reflex control of muscles is autonomous
Means it happens whether you’ve got a brain or not, reflex control is hardwired into motor neurone circuits at each segmental spinal level
What is the vestibulospinal tract involved in
Balance
What is the reticulospinal tract involved in
Takes visual input and regulates trunk and limb muscle reflexes from this
Brainstem nuclei can override spinal reflexes but where do they receive their control inputs about voluntary movements from
Higher centres - the cerebral cortex (motor cortex and premotor and supplementary motor areas), the basal ganglia and the cerebellum
What tracts do the ventromedial pathways consist of (4)
Tectospinal tract
Vestibulospinal tract
Pontine reticulospinal tract
Medullary reticulospinal tract
What is the tectospinal tract involved in
ensures eyes remain stable as body moves
What 2 tracts control posture and locomotion
Vestibulospinal + tectospinal
What 2 tracts control trunk and antigravity muscles
Pontine and medullary reticulospinal tracts
What 2 white matter tracts do the lateral pathways consist of
Corticospinal
Rubrospinal
What fraction of the corticospinal tract is motor and somatosensory
2/3 motor
1/3 somatosensory
Where does the rubrospinal tract begin
Red nucleus in midbrain
If there’s a lesion of the corticospinal tract, what tract can take over
Rubrospinal
Neurons of the CST … excite pools of … motorneurons
The same neurons branch and via …, inhibit pools of … motorneurons
monosynaptically
agonist
interneurons
antagonist
Medial LMNs control axial/proximal or distal limb muscles so medial tracts are more responsible for control of posture + balance or precise voluntary movements
axial/ proximal
Posture + balance
Lateral LMNs control axial/proximal or distal limb muscles
Distal
UMNs from brainstem travel in what pathways synapsing with LMNs in what part of spinal cord
Ventromedial
Lateral ventral horn
UMNs from cortex travel in what pathways synapsing with LMNs in what part of spinal cord
Lateral pathways (CST & RST)
Medial ventral horn
Premotor cortex (Area 6) subdivided in what 2 areas
Premotor area
Supplementary area
Planning of movement by the cerebrum requires 3 things
Where the body is in space (proprioceptive and visual input)
Where it wants to go
Selecting a plan to get there
What is area 7 of the brain
Visuo-motor co-ordination area
Decision making, what movement to take + their likely outcome occurs in what areas of the brain (2)
Input from these 2 areas converges onto what area + what happens there
Prefrontal cortex
Somatosensory cortex
Area 6 - premotor cortex, signal is converted into how it’s going to be carried out by decision making neurons in area 6
