Motor Control 1 Flashcards
(23 cards)
What is the function of the high level of motor control?
What structures does this involve?
- Strategy: what is the goal and how to accomplish it
- Association neocortex, basal ganglion
What is the function of the middle level of motor control?
What structures does this involve?
- Determining the sequence of spatiotemporal muscle contractions needed to accomplish a goal smoothly
- Motor cortex and cerebellum
What is the function of the low level of motor control?
What structures does this involve?
- Execution: activation of motor neuron and interneuron pools to generate movement
- Brain stem, spinal cord
What are the different (motor) pathways that link the brain and spinal cord? What do they control?
- Lateral pathways: control voluntary movements of distal muscles, under direct cortical control
- Ventromedial pathways: control posture and locomotion, under brainstem control
What are the lateral pathways? Where do they originate? Receive input from?
- Corticospinal tract (CST) - originates at areas 4 & 6, input from same place
- Rubrospinal tract (RST) - originates at red nucleus of midbrain, receives input from areas 4 & 6
What happens if there is a lesion in the CST?
- Fine movements of limbs lost
- Functions reappear after a few months if the RST is still in tact, if there is also a lesion there functions are permanently lost
Describe the action of pyramidal neurons in the CST
- They monosynaptically excite agonist motoneuron pools
- The same neurons branch and activate inhibitory interneurons which inhibit antagonist motor neuron pools
What are the ventromedial pathways?
- Tectospinal tract (head and eye)
- Pontine reticulospinal tract
- Vestibulospinal tract
- Medullary reticulospinal tract
Function of the vestibulospinal tract?
change the position of the limbs and head with the goal of supporting posture and maintaining balance of the body and head
Function of the tectospinal tract?
Ensure eyes remain stable as the body moves
Where do the pontine and medullary reticulospinal tracts originate?
What do they innervate and what is their function?
Originate in the brainstem (pontine - pons, medullary - medulla)
Innervate the trunk and antigravity muscles in the limbs to reflexly maintain balance and body position
When undergoing complex voluntary movements how do the motor cortex and reflex centres interact?
The motor cortex can free spinal neurones from reflex control via interactions with ventromedial nuclei
Where do the axons of upper motor neurons from the motor cortex lie in the spinal cord?
Laterally - in the white matter
lateral to grey matter
Where do axons of upper motor neurons from brainstem lie in the spinal cord?
Ventromedially - in the white matter
Which muscles do LMN’s originating from the medial grey matter control?
LMN’s originating from lateral grey matter?
Medial - control proximal muscles
Lateral - control distal muscles
Where is the primary motor cortex in the brain?
Where are the premotor and supplementary motor areas?
- Primary motor: precentral gyrus, area 4
- Premotor/supplementary motor: anterior to precentral gryus, area 6
How are the neurons of area 6 organized?
Area 6 divided into premotor area (PMA) and supplementary motor area (SMA)
Each of these has their own somatotopic organization, two motor maps in area 6
Is the somatotopic motor map precise?
Not really
Maps seem to represent movements instead of upper motor neurons causing individual muscle movements
- Eg. if you stimulate an area of area 4, can cause the movement of hand to mouth, not just the flexion of a single muscle as somatotopic rep would suggest
Where in the brain is our image of body in space generated?
In the posterior parietal cortex (areas 5 & 7)
- generated from somatosensory, proprioceptive and visual inputs
Which parts of the brain are responsible for making decisions on which actions/movements to make and their likely outcome?
Where do axons from these areas converge?
- Prefrontal and parietal cortexes
- Axons converge onto area 6, converts desired actions into “how to carry this out”
If you only think about actions instead of doing them, is area 4 or area 6 active?
Area 6
Area 4 is for doing actions, activating the CST & RST
When do PMA neurons start firing when making a movement?
Start firing a second before movement occurs, continue to fire throughout the movement
Slide says: “they are decision making neurones in command centres” but everywhere else seems to say that it just plans movements
Which neurons fire when we watch another person do something? What may this suggest?
Neurons in area 6 fire
May suggest that these neurons not only plan our movements but may give us insight into the intentions of others with their movements (may be dysfunctional in autism)
