Motor Control I

Question 1

Motor Control is a functional hierarchy with 3 levels. what are the three levels?

Answer 1

high, middle and low

Question 2

what is the function and structures involved in the high level?

Answer 2

Strategy Association neocortex, basal ganglion

Question 3

what is the function and structures involved in the middle level?

Answer 3

Tactics

Motor cortex, cerebellum

Question 4

what is the function and structures involved in the low level?

Answer 4

Execution

Brain stem, spinal cord

Question 5

what does ‘strategy’ mean in regards to the function of the high level?

Answer 5

Strategy – the goal and the movement strategy to best achieve this goal

Question 6

what does ‘tactics’ mean in regards to the function of the middle level?

Answer 6

Tactics – the sequence of spatiotemporal muscle contractions to achieve a goal smoothly and accurately

Question 7

what does ‘execution’ mean in regards to the function of the low level?

Answer 7

Execution – activation of motor neuron and interneuron pools to generate goal-directed movement

Question 8

what does the lateral pathways do?

Answer 8

control voluntary movements of distal muscles – under direct cortical control

Question 9

what does the ventromedial pathways do?

Answer 9

control posture and locomotion - under brain stem control

Question 10

what tract is involved in the lateral pathway?

Answer 10

Cortocospinal tract (CST) – hugely important - longest, amongst largest tracts (~1 million axons)

Question 11

where does the CST originate from?

Answer 11

2/3 of CST originates in areas 4 and 6 of the frontal motor cortex – the rest is somatosensory

Question 12

where and why does the CST decussates?

Answer 12

at medulla/spinal cord junction, the CST crosses over (decussates), so that –

the right motor cortex controls the left side and the left motor cortex controls the right side

Question 13

where does the CST axons synapse?

Answer 13

ventral horn motor neurones and interneurones to control muscles voluntarily.

Question 14

where does the rubrospinal tract start?

Answer 14

A much smaller rubrospinal tract (RST) starts in the red nucleus of midbrain and receives inputs from same cortical areas as the CST.

Question 15

what does a Lesion to CST and RST cause?

Answer 15

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

Question 16

what does a Lesion to CST alone cause?

Answer 16

– same deficits seen, but after a few months functions reappear.

Question 17

where do Large pyramidal neurones in motor cortex project via

Answer 17

CST

Question 18

function of large pyramidal neurones in motor cortex?

Answer 18

They monosynaptically excite pools of agonist motoneurones

Question 19

True or false:

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

Answer 19

true

Question 20

function of the vestibulospinal tract?

Answer 20

VST stabilizes head and neck

Question 21

function of tectospinal tract?

Answer 21

TST ensures eyes remain stable as body moves

Question 22

what is Pontine and medullary reticulospinal tracts?

Answer 22

Originate in brain stem

Use sensory information about balance, body position and vision

Reflexly maintain balance and body position

Innervate trunk and antigravity muscles in limbs

Question 23

what do voluntary movements require?

Answer 23

inputs from motor cortex via lateral pathways

Question 24

can motor cortex activate spinal motoneurons directly?

Answer 24

yes

Question 25

function of the motor cortex

Answer 25

can activate spinal motoneurons directly

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

Question 26

what plans and controls precise voluntary movements?

Answer 26

Primary motor cortex and pre-motor areas

Question 27

what do Upper motor neurons in cortex and brainstem target?

Answer 27

lower motor neurons in the spinal cord

Question 28

Lower motor neurone distribution is…

Answer 28

somatotopic

Question 29

what do medial white matter control?

Answer 29

axial and proximal limb muscles

Question 30

what do lateral white matter control

Answer 30

innervate distal limb muscles

Question 31

where are the axons from, involved in lateral white matter?

Answer 31

motor cortex

Question 32

where are the axons from, involved in medial white matter?

Answer 32

brainstem

Question 33

medial tracts from brainstem control…

Answer 33

posture balance and orienting mechanisms.

Question 34

lateral tracts from cortex control…

Answer 34

precise skilled voluntary movements.

Question 35

origin of upper motor neurons?

Answer 35

cerebral cortex

brainstem

Question 36

destination of UMN’s

Answer 36

cerebral cortex to LMN’s in lateral ventral horn

brainstem to LMN’s in medial ventral horn

Question 37

where is the primary motor cortex?

Answer 37

in the precentral gyrus

Question 38

what does sytematic probing of area 4 cause?

Answer 38

primary motor cortex revealed somatotopic organisation of precentral gyrus

Question 39

what does the supplementary motor area innervate?

Answer 39

distal motor units directly

Question 40

what does the premotor area connect with?

Answer 40

reticulospinal neurones innervating proximal motor units

Question 41

Microstimulation in specific area of primary motor cortex (area 4) elicits…

Answer 41

coordinated movements of hand and mouth or

(B) movements that bring hands into central space to inspect/manipulate objects.

Question 42

mental image of body in space is generated by

Answer 42

somatosensory, proprioceptive and visual inputs to posterior parietal cortex (areas 5 and 7).

Question 43

what happens at the prefrontal and parietal cortex?

Answer 43

where decisions are taken -

which actions/movements to take and their likely outcome

Question 44

what are the functions of the axons that converge on area 6

Answer 44

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