Motor control 1 Flashcards

1
Q

Identify the different functional areas of the brain in the diagram below

A
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2
Q

Motor control is a functional hierarchy and can be described as having 3 levels (high, medium, low)

Describe the 3 levels of motor control

A

High - Strategy:

  • Concerned with Strategy - ie the goal and movement strategy to best achieve this

Medium - Tactics:

  • Concerned with Tactics - the sequence of spatiotemporal muscle contractions to achieve a goal smoothly and accurately

Low - Execution:

  • Concerned with execution - ie activation of motor neuron and interneuron pools to generate goal-directed movement
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3
Q

What areas of the Nervous system are involved with the 3 levels of motor control?

A

High (Strategy):

  • Association neocortex - eg Broca’s etc
  • Basal ganglia

Medium (Tactics):

  • Motor cortex
  • Cerebellum

Low (execution):

  • Brainstem
  • Spinal cord
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4
Q

Shown in the diagram below are two sets of motor tracts in the spinal cord

What names are given to these pathways and what are their purposes?

A

Lateral Pathways:

  • Control voluntary movements of distal muscles (remember the spatial mapping?)
  • These movements are under direct cortical control

Ventromedial pathways:

  • These control posture and locomotion
  • Under brainstem control
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5
Q

What are the contents of the Corticospinal tract? (CST)

A

2/3rds of the CST originates in areas 4 & 6 of the frontal motor cortex

The rest is somatosensory

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6
Q

Where do the axons contained within the CST synapse?

A

CST axons synapse on ventral horn motor neurones and interneurones to control muscles voluntarily

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7
Q

What other important tract is contained within the Lateral pathways of the spinal cord?

A

Rubrospinal tract (RST):

  • Starts in the red nucleus of midbrain
  • Receives inputs from same cortical areas as the CST (4 & 6)
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8
Q

What is the effect of lesions to the CST and/or RST?

A

fine movements of arms and hands are lost. Can’t move shoulders, elbows, wrist and fingers independently.

If only CST injured - RST can take over after a while so functions re-appear

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9
Q

Identify the labels innit

A
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10
Q

What are motor neuron pools?

A

A motor pool consists of all individual motor neurons that innervate a single muscle

As muscles often work in agonist-antagonist pairs, flexor motor pools are close to extensor pools etc

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11
Q

Describe the action of descending pathway axons (eg those of the CST) on motor neuron pools

A

They monosynaptically excite pools of agonist motoneurones

The same pyramidal neurones branch and via interneurons inhibit pools of antagonist motoneurones

(Similar to that of the crossed extensor reflex)

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12
Q

What is the purpose of the Vestibulospinal and tectospinal tracts?

A

Vestibulospinal:

  • Stabilizes head and neck (think of a figure skater)
  • Originates from Vestibular nucleus

Tectospinal:

  • TST ensures eyes remain stable as the body moves
  • Originates from superior colliculus
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13
Q

What is the purpose of the Pontine and Medullary Reticulospinal tracts?

A

These are ventromedial pathways controlling the trunk and antigravity muscles

Originate in the brainstem (pons & medulla) and use sensory information about balance, body position and vision to Reflexly maintain balance and body position

Innervates the trunk and anti-gravity muscles in the limbs

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14
Q

Identify the labels in the diagram of the pontine and medullary reticulospinal tracts

A
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15
Q

How does the motor cortex prevent reflexes from fucking up all the voluntary movements that we talked about

A

motor cortex can also free spinal neurones from reflex control - by interactions with the nuclei of the ventromedial pathways

eg Reticular nuclei, superior colliculus, vestibular nuclei

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16
Q

Lower motor neuron arrangement is described as being somatotopic

What does somatotopic mean?

A

point-for-point correspondence of an area of the body to a specific point on the central nervous system

17
Q

What is the significance of area 6 in the brain?

A

Area 6 = Pre-motor and supplementary motor areas

18
Q

Identify the functional areas of the brain in the diagram below

A
19
Q

In order for us to do that voluntary movement stuff - what 3 things do we need to know for our motor cortex to plan the movement?

A

1) Where the body is in space
2) Where we want to go/move
3) The plan of action to get there

20
Q

Epileptic seizures often ‘march’ across the body - starting with fingers and finishing at the face for example

What is the link between the motor homunculus and this?

A

The seizure will roughly move along the motor cortex’s somatotopic arrangement (motor homunculus)

However, the somatotopic map is not as simple as ‘this point in PMC = Bicep and this other point = yer toe muscle’

(more on that in a sec)

21
Q

What are the 2 motor maps of area 6?

A

One of the Pre-motor area

One of the Supplementary motor area

Remember that both the PMA and SMA make up area 6

22
Q

What do the PMA and SMA innervate?

A

SMA innervated distal motor units directly

PMA connects with reticulospinal neurones innervating proximal motor units

23
Q

In what way is the somatotopic arrangement of the motor cortex not precise?

A

it does not represent upper motor neurones causing individual muscle movements

functional maps of the cortex appear to map movements – perhaps (in area 6) even the intention of a complete movement

24
Q

So in reality, if you were to stick an electrode into specific areas of the motor cortex - what would happen?

A

Microstimulation of specific parts of area 4 elicits:

  • Coordinated movements of hand or mouth
  • Movements that bring hands into central space to inspect/manipulate objects

These are in the contralateral limb to the area being stimmed

Movements seem to follow 3 basic goals - to inspect, to manipulate or to defend

25
Q

Identify the areas in the diagram and describe their role in body movements

A

Posterior parietal cortex (5 & 7):

  • This is where the mental image of the body in space is generated
  • The image is generated from somatosensory, proprioceptive and visual inputs

Prefrontal and parietal cortex are where decisions are taken:

  • which actions/movements to take and their likely outcome
26
Q

The Posterior parietal cortex and pre-frontal cortex must communicate with the rest of the brain obviously

How do they do this?

A

Axons (association fibres?) from PPC and PFC converge on area 6

Here signals encoding desired actions are converted into how to carry this out

27
Q

What is meant by ‘mirror neurones’

A

Neurones in the PMA fire when we think about doing a movement (even if we dont do it)

However - they also fire when we watch another person do the same task

  • Thus they are mirroring the PMA firing of the person doing the task

This is what allows us to understand other’s movement:

  • It may also be the foundation of Empathy
  • May be dysfunctional in those with autism