Wk 5 - Motor Control Flashcards
Levels of the motor system, from muscle to neocortex (x7)
Spinal motor units Brain stem motor nuclei Cerebellum Basal ganglia Primary motor cortex Secondary motor cortex Association cortex
Describe the characteristics of the motor system model (x5)
Parallel, hierarchical, circuit
Discrete functional areas
Sensory feedback up each level and back again (modulates output)
Lowest level of the motor system hierarchy is (name and describe x1)
motor unit = motor neurone and the muscle fibre(s) it innervates
Point of muscle innervation is (Name and describe x1)
Neuromuscular junction: motor end plate is where axon branches to synapse with muscle
NT for muscular activation is… (x1)
Ach
Two descending motor pathways are…
Dorsolateral tracts
Ventromedial tracts
Two types of dorsolateral tracts (in descending motor pathway)
Corticospinal tracts
Corticorbrospinal
Dorsolateral tracts of descending motor pathway terminate (x2) And control (x1)
Contralateral half of spinal cord
Sometimes directly on motor neuron
Movement of distal limbs
Lawrence and Kuypers 1968 transected dorsolateral corticospinal tracts in medullary pyramids of monkeys, and found… (x3)
Could stand, walk and climb
But not other activities – reaching for objects, independent finger movement
(still proximal limb function)
Corticospinal tracts (descending motor pathway, dorsolateral tract) are (x4)
Direct pathway from cortices,
Through medullary pyramid (where they cross over to gives contralateral control),
To dorsolateral portion of spinal cord,
Then distal limb muscles
Coriticorubrospinal tracts (descending motor pathway, dorsolateral tract) are (x4)
Indirect pathways from cortex
Through red nucleus (crossover occurs here),
Down to nuclei of cranial nerve motor neurons (splitting out to contralateral facial muscles),
Before continuing to contralateral distal limb muscles
Two types of ventromedial tracts (in descending motor pathway)
Ventromedial corticospinal tracts
Cortico-brainstem-spinal tracts
Ventromedial tracts (describe x1, location x1, and function x 3)
More diffuse;
Axons innervate interneurons in several spinal cord segments;
Do the trunk and upper legs,
And posture and whole-body movements,
And limb movements involved in those activities
Lawrence and Kuypers 1968 transected ventromedialtracts in monkeys, finding (x2)
Postural abnormalities and impaired walking and sitting,
But could pick up food and small objects
Ventromedial corticospinal tracts (descending motor pathway, ventromedial tract) are (x3)
Direct pathways from cortex
Down to ipsilateral ventromedial portion of spinal cord (the forward centre of spine),
Then become diffuse to trunk and proximal limb muscles
Cortico-brainstem-spinal tracts (descending motor pathway, ventromedial tract) are (x7)
Indirect path from cortex,
Through tectum,
Then reticular formation, vestibular nucleus and cranial motor nerves;
Then bilaterally to ventromedial spinal cord,
And proximal limb muscles
Functions of the basal ganglia remain elusive because… (x3)
and are therefor termed (x1)
High number of structures,
Each nucleus can be inhibitory or excitatory – modulate each other
So difficult to isolate one structure/define its functions
Complex heterogenous interconnected nuclei
The cerebellum/’little brain’ receives input from (x2)
And feedback from (x2 systems plus functions)
Primary and secondary motor cortex
Somatosensory – vision, touch, hearing, smell; and
Vestibular – which way your pointing, how fast you’re moving
The cerebellum/’little brain’ is important for (x5)
Learning of routines Navigation, Walking/gait – smooth movements, Speech and Balance,
Functions of the basal ganglia/’mysterious basement’ remain elusive because… (x3)
and are therefor termed (x1)
High number of structures,
Each nucleus can be inhibitory or excitatory – modulate each other
So difficult to isolate one structure/define its functions
Complex heterogenous interconnected nuclei
The cerebellum/’little brain is important for (x6)
Learning of routines - fine-tuning and learning functions, Navigation, Cognitive functions of routines too, Walking/gait – smooth movements, Speech and Balance,
Dysfunction of the cerebellum can lead to (name and symptoms x2)
Cerebellar ataxia
Wide-based gait
Stumble a little side to side to keep balance
Function of the basal ganglia (x2)
And is important for… (x1 plus 3 egs)
Modulate movement, plus Cognitive functions
Habitual/implicit responses/routines, eg instruments, typing, dancing
Indirect pathways of the basal ganglia run… (x2)
From primary motor cortices,
Also to thalamus
Direct pathways from the basal ganglia run… (x4)
Through thalamus,
Then supplementary motor area,
And on to primary motor cortices
(connected by direct pathway through corpus callosum)
The supplementary motor area has turned out to be… (x2)
Plus eg
Several areas, acts as gatekeeper
(actions selected at lower levels, then released by supplementary to primary areas)
All objects on your desk elicit potential for action, appropriate ones get released, others get inhibited
Direct and indirect pathways from the basal ganglia depend on (x1)
Whose connections can be… (x2)
Dopaminergic connections from substantia nigra
Excitatory OR inhibitory:
Output of one nucleus either excites (enhances) or inhibits (suppresses) the output of the next nucleus