Motor Control 1 Flashcards
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What are lateral pathways responsible for?
Lateral pathways control voluntary movements of distal muscles – under direct cortical control
What are ventromedial pathways responsible for?
Control posture and locomotion under brainstem control
What pathways come under lateral spinal tract?
Corticospinal
Rubrospinal
What pathways come under ventromedial pathways?
Tectospinal
Vestibulospinal
Pontine reticulospinal
Medullary Reticulospinal
Where does 2/3rds of the CST originate?
In areas 4 and 6 of the frontal motor cortex, the rest is somatosensory
Where does the CST decussate?
Decussates at the medulla - spinal cord junction
Where do CST axons synapse?
Ventral horn motor neurones and interneurones
Where does the rubrospinal tract start?
Starts in the red nucleus of midbrain - inputs from same cortical areas as CST
What is the result of a lesion in the CST and RST?
- Fine movements of arms and hands lost. Can’t move shoulders, elbows, wrist and fingers independently.
What is the result of a lesion in the CST alone?
•same deficits, but after few months functions reappear. Been taken over by RST, because if now lesion RST – lose restored functions.
What are the two ventromedial pathways that control posture and locomotion?
Vestibulospinal and tectospinal
What is the VST responsible for?
Stabilizes head and neck
What is the TST responsible for?
Ensures eyes remain stable as body moves
Where do pontine and medullary reticulospinal tracts originate?
Brainstem
What is the function of the pontine and medullary reticulospinal tracts?
Use sensory information about balance, body position and vision
Reflexly maintain balance and body position
Innervate trunk and antigravity muscles in limbs
What is the relationship between the motor cortex and the ventromedial pathways?
During an action like throwing, the motor cortex directly activates the spinal motoneurones and frees them from reflex control by communicating via the nuclei of ventromedial pathways.
What do the primary motor cortex and pre-motor areas fo?
Plan and control precise voluntary movements
Describe the distribution of lower motor neurones
Somatotopic
Medial lower motor neurones - control axial and proximal limb muscles
Lateral lower motor neurones - control distal limb muscles
What is the function of the medial and lateral tracts?
Medial tracts are from the brainstem - control posture balance and orienting mechanisms
Lateral tracts are from the cortex - they control precise skilled voluntary movements
Summary
What are the following landmarks on the brain?
What makes up Broddman area 6?
The pre-motor area and the supplementary motor area
What is the function of area 6?
Drives complex movements on either side of the body
What is the result of weak electrical stimulation of area 4?
Twitch of contralateral muscles - demonstrates somatotopic organistaion of precentral gyrus
What is the function of the supplementary motor area?
Innervates distal motor units directly
What is the function of the PMA?
•PMA connects reticulospinal neurones innervating proximal motor units
What are the two effects of microstimulation of the primary motor cortex?
(A) coordinated movements of hand and mouth
or
(B) movements that bring hands into central space to inspect/manipulate objects
How is a mental image of the body in space generated?
Generated by somatosensory, proprioceptive and visual inputs into the posterior parietal cortex (areas 5 and 7)
Damage to what area causes neglect of one side of the body?
Damage to areas 5 and 7, responsible for creating an image of the body in space
Where are decisions made about what actions/movements to take and their likely outcome?
Prefrontal cortex and parietal cortex
•axons from both converge on area 6. This is the junction where signals encoding what actions are desired are converted into how the actions will be carried out.
What is the difference between areas 4 and 6?
• if you only think about movements - area 6 is active but area 4 is not: area 4 is for “doing it” by activating the neurones of the CST and RST
When are the three occasions neurones fire from area 6?
When movement is made
When movement is imagined
When others make the same specific movement
