Motor Control

Question 1

What are the structures involved in strategy of voluntary movements?

Answer 1

Association neocortex

Basal ganglion

Question 2

What are the structures involved in tactics of voluntary movements?

Answer 2

Motor cortex

Cerebellum

Question 3

What are the structures involved in execution of voluntary movements?

Answer 3

Brain stem

Spinal cord

Question 4

What is the function of lateral pathways?

Answer 4

Control voluntary movements of distal muscles

Under direct cortical control

Question 5

What is the functions of ventromedial pathways?

Answer 5

Control posture and locomotion

Under brain stem control

Question 6

Where does the corticospinal tract originate?

Answer 6

2/3 in areas 4 + 6 of frontal motor cortex

Rest is somatosensory

Question 7

Where does the corticospinal tract cross over?

Answer 7

Medulla/spinal cord junction

Question 8

Where does corticospinal tract axons synapse to control muscles voluntarily?

Answer 8

Ventral horn motor neurones

Interneurones

Question 9

Where does the rubrospinal tract start?

Answer 9

Red nucleus of the midbrain

Question 10

Where does the rubrospinal tract receive input from?

Answer 10

Same cortical areas as the corticospinal tract

Question 11

What happens when there is lesions to corticospinal and rubrospinal tracts?

Answer 11

Fine movements of arms and hands lost

Can’t move shoulders, elbows, wrist and fingers independently

Question 12

What happens where there is a lesion to the corticospinal tract alone?

Answer 12

Same as CST + RST lesion
BUT after few months functions reappear
RST takes over

Question 13

What is the role of the vestibulospinal tract?

Answer 13

Stabilises head and neck

Question 14

What is the role of the tectospinal tract?

Answer 14

Ensures eyes remain stable as body moves

Question 15

Where do pontine and medullary recticulospinal tracts originate?

Answer 15

Brain stem

Question 16

What type of sensory information does the pontine and medullary reticulospinal tracts use?

Answer 16

Balance
Body position
Vision

Question 17

What is the role of the pontine and medullary reticulospinal tracts?

Answer 17

Reflexly maintain balance and body position

Innervate trunk and antigravity muscles in limbs

Question 18

What do voluntary movements require input from?

Answer 18

Motor cortex via lateral pathways

Question 19

What is the role of primary motor cortex and pre-motor areas?

Answer 19

Plan and control precise voluntary movements

Question 20

What do medial lower motor neurones control?

Answer 20

Axial and proximal limb muscles

Question 21

What do lateral lower motor neurones do?

Answer 21

Innervate distal limb muscles

Question 22

Where is the primary motor cortex located?

Answer 22

Precentral gyrus

Question 23

What does the supplementary motor area innervate?

Answer 23

Distal motor units directly

Question 24

What does the premotor area connect with?

Answer 24

Reticulospinal neurones innervating proximal motor units

Question 25

What are the areas of cortex involved in planning and instructing voluntary movement?

Answer 25

``` Prefrontal cortex Area 6 (SMA, PMA) Area 4 Central sulcus S1 Posterior parietal cortex (Areas 5 + 7) ```

Question 26

What does microstimulation in specific area of primary motor cortex induce?

Answer 26

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

Question 27

What type of inputs are required to form a mental image of body in space?

Answer 27

Somatosensory, propriceptive and visual inputs to the posterior parietal cortex

Question 28

Where are decisions taken about which actions/movements to take and their likely outcome?

Answer 28

Prefrontal and parietal cortex

Question 29

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

Answer 29

Axons from prefrontal and parietal cortex converge on area 6

Question 30

When do PMA mirror neurones fire?

Answer 30

When self or others perform specific actions | Allows understanding of actions or intentions of others

Question 31

How is postural instability corrected with a change in body position?

Answer 31

Rapid compensatory feedback messages from brainstem vestibular nuclei to spinal cord motor neurons

Question 32

What happens before movements begin to stabilise position?

Answer 32

Brainstem reticular formation nuclei initiate feedforward anticipatory adjustments

Question 33

What are the signs of UMN damage?

Answer 33

``` Flaccidity of contralateral muscles Increased muscle tone Hyperactive stretch reflex Clonus Loss of fine finger movements ```

Question 34

What is the role of the basal ganglia motor loop?

Answer 34

Selects and initiates willed movements

Question 35

Where does the major subcortical input to area 6 come from?

Answer 35

Ventral lateral nucleus in dorsal thalamus (VLo)

Question 36

Where does input to the VLo come from?

Answer 36

Basal ganglia

Question 37

What are the major components of basal ganglia?

Answer 37

``` Corpus striatum (caudate + putamen) = input zone Corticostriatal pathway ```

Question 38

What do the medium spiny neurones in the putamen and caudate receive?

Answer 38

Excitatory (glutamatergic) cortical inputs on dendrites

Question 39

When does the putamen fire?

Answer 39

Before limb/trunk movements

Question 40

When does the caudate fire?

Answer 40

Before eye movements

Question 41

What type of pathway connects the cortex to the putamen?

Answer 41

Excitatory pathway

Question 42

What type of pathway connects the putamen to the globus pallidus?

Answer 42

Inhibitory

Question 43

What type of pathway connects the globus pallidus to the VLo neurones?

Answer 43

Inhibitory

Question 44

What type of pathway connects VLo back to the SMA?

Answer 44

Excitatory

Question 45

What do globus pallidus neurones do at rest?

Answer 45

They are spontaneously active and inhibit VLo

Question 46

What does cortical excitation do?

Answer 46

Excites putamen which inhibits the inhibitory globus pallidus = releases cells in VLo from inhibition so activity in VLo boosts SMA activity

Question 47

What does the direct pathway through the basal ganglia act as?

Answer 47

Positive feedback loop 'GO' signal to SMA in cortex Enhances initiation of movements by SMA

Question 48

What is the role of the indirect pathway through the basal ganglia?

Answer 48

Antagonises the direct route Striatum inhibits external GP which inhibits both internal GP and subthalamic nuclei Cortex excites STN = excites GPi = inhibits thalamus

Question 49

What is the purpose of the direct pathway through the basal ganglia?

Answer 49

Selects specific motor actions

Question 50

What is the purpose of the indirect pathway through the basal ganglia?

Answer 50

Suppresses competing/inappropriate action

Question 51

What is hypokinesia?

Answer 51

Slowness Difficult to make voluntary movements Increased muscle tone Tremors of hand and jaw

Question 52

What causes hypokinesia?

Answer 52

Degeneration of neurones in substantia nigra and their dopaminergic inputs to the striatum

Question 53

What is the role of dopamine?

Answer 53

Enhances cortical inputs through the 'direct' pathway and suppress inputs through 'indirect' pathway

Question 54

What happens to dopamine in Parkinsons?

Answer 54

Depleted which closes down activation of the focussed motor activities that funnel through the thalamus to the SMA

Question 55

What does Huntington's disease involve?

Answer 55

Hyperkinesia Dementia Personality disorders

Question 56

What is characteristic chorea?

Answer 56

Spontaneous, uncontrolled, rapid flicks and major movements with no purpose

Question 57

What causes characteristic chorea?

Answer 57

Profound loss of caudate, putamen and globus pallidus

Question 58

How does lesions to the cerebellum affect movement?

Answer 58

Produces uncoordinated inaccurate movements

Question 59

What areas make up a part of the huge cortico-ponto-cerebellar projection?

Answer 59

Layer 5 Areas 4 + 6 Somatosensory cortex

Question 60

What is the role of the cerebellum in movement?

Answer 60

Instructs direction, timing and force of movement