motor control 1

Question 1

what are the 3 levels of motor control hierarchy?

Answer 1

high
middle
low

Question 2

what are the structures associated with high motor control?

Answer 2

association neocortex

basal ganglia

Question 3

what are the structures associated with middle motor control?

Answer 3

motor cortex

cerebellum

Question 4

what are the structures associated with low motor control?

Answer 4

brainstem

spinal cord

Question 5

what do the lateral pathways of the spinal cord control?

Answer 5

voluntary movements of distal muscles - under direct cortical control

Question 6

what do ventromedial pathways control?

Answer 6

posture and locomotion - under brain stem control

Question 7

where does the corticospinal tract decussate?

Answer 7

medulla/spinal cord junction

Question 8

how do CST axons control muscles?

Answer 8

they synapse on ventral horn motor neurones and interneurons

Question 9

where does 2/3ds of the CST originate?

Answer 9

areas 4 and 6 of the frontal motor cortex - rest is somatosensory

Question 10

where does the rubrospinal tract originate?

Answer 10

red nucleus of the midbrain

Question 11

what happens if there are lesions in the CST and RST?

Answer 11

fine movements of the arms and hands lost.

unable to move shoulders, elbows, wrist and fingers independently

Question 12

what happens if there is a lesion in the CST but not the RST?

Answer 12

fine movements initially lost but after a few months functions reapper because the RST takes over

Question 13

what does the vestibulospinal tract do?

Answer 13

stabilizes head and neck

Question 14

what does the tetospinal tract do?

Answer 14

ensures eyes remain stable as body moves

Question 15

where do the pontine and medullary reticulospinal tracts originate?

Answer 15

brainstem

Question 16

what sensory information do the pontine and medullary Reticulospinal tracts use?

Answer 16

balance
body position
vision

Question 17

what is the function 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 does the motor cortex do when complex movement is required?

Answer 18

directly activates spinal motoneurones and frees them from reflex control by communicating via nuclei of ventromedial pathways

Question 19

where do the medial tracts of white matter originate?

Answer 19

brainstem

Question 20

where do the lateral tracts of white matter develop?

Answer 20

cortex

Question 21

where in the brain is the primary motor cortex?

Answer 21

precentral gyrus

Question 22

what does the cerebral cortex need to know in order to plan movement?

Answer 22

where the body is in space
where it wants to go
needs to select a plan to get there

Question 23

what is the function of the supplementary motor area?

Answer 23

innervates distal motor units directly

Question 24

what is the function of the premotor area?

Answer 24

connects reticulospinal neurones innervating proximal motor units

Question 25

why is area 6 of the brain sometimes described as a "junction"?

Answer 25

it is where signals encoding what actions are desired are converted into how the actions will be carried out

Question 26

what happens with regard to blood flow to the brain during practised voluntary finger movements?

Answer 26

``` blood flow increases in the following areas: somatosensory posterior parietal prefrontal cortex areas 6 and 4 ```

Question 27

if you were to "think" about making a movement, which area would be active?

Answer 27

area 6 but not area 4- area 4 is for "doing it"

Question 28

what are the decision making neurones in command centres?

Answer 28

neurones in the premotor area

Question 29

when are neurones in area 6 fired?

Answer 29

during movement when movement is imagined when you see others making a specific movement

Question 30

how is the direction of movement decided?

Answer 30

neurone discharge is greatest in a preferred direction each neurone has a preferred direction but responses of all neurons are combined to produce a population vector overall movement direction is encoded by the integrated activity of all neurones

Question 31

what does a change in body position initiate in regard to feedback?

Answer 31

messages from brainstem vestiblar nuclei to spinal cord motor neurones to correct postural instability

Question 32

what must happen before movements to change body position start?

Answer 32

brainstem reticular formation nuclei (controlled by the cortex) initiate feed forward anticipatory adjustments to stabilize posture

Question 33

what does cortical damage cause?

Answer 33

immediate flaccidity of contralateral muscle

Question 34

what causes initial hypotonia?

Answer 34

spinal circuits being derived of cortical input

Question 35

how do spinal circuits manage to regain their function in spinal shock?

Answer 35

days later, spared connections strengthen and new connection sprout - consistent pattern of motor signs emerges

Question 36

what does the babinski sign indicate?

Answer 36

incomplete upper control of spinal circuits

Question 37

what results in spasticity?

Answer 37

removal of cortical suppressive influences

Question 38

where does the major subcortical input to area 6 of the brain come from?

Answer 38

ventral lateral nucleus in dorsal thalamus

Question 39

what is the basal ganglia motor loop?

Answer 39

information cycles from the cortex through the thalamus and basal ganglia, then back to the SMA in cortex

Question 40

what are the major components of basal ganglia?

Answer 40

corpus striatum

Question 41

what is the input zone of the basal ganglia?

Answer 41

caudate | putamen

Question 42

where does the corpus striatum receive input from?

Answer 42

all over the cortex; the corticostriatal pathway is made up of multiple parallel pathways with different functions

Question 43

where are medium spiny neurones located?

Answer 43

putamen and caudate

Question 44

what kind of signals do medium spiny neurones receive on their dendrites?

Answer 44

excitatory cortical inputs

Question 45

what kind of inputs do medium spiny neurones integrate?

Answer 45

somatosensory premotor motor cortical

Question 46

where do the axons of medium spiny neurones project to?

Answer 46

globus pallidus substantia nigra pars reticula

Question 47

when do the neurones of the putamen fire?

Answer 47

before limb/trunk movements

Question 48

when do the neurones of the caudate fire?

Answer 48

before eye movements

Question 49

what is the functional consequence of cortical activation of the putamen?

Answer 49

excitation

Question 50

how does cortical activation of the putamen result in an excitatory signal being sent to the SMA?

Answer 50

putamen sends inhib signal to globus pallidus globus pallidus sends inhib signal to VLo VLo then sends excitatory signal to the SMA

Question 51

what do globus pallidus neurones do at rest?

Answer 51

inhibit the VL signal

Question 52

what is the effect of inhibiting the globus pallidus?

Answer 52

releases cells in VLo from inhibition so activity in VLo boosts SMA activity

Question 53

how does the indirect basal ganglia loop work?

Answer 53

antagonizes the direct route: | striatum inhibits globus pallidus externa which then inhibits the GPi and the subthalamic nuclei

Question 54

what effect does exciting the subthalamic nuclei have

Answer 54

excites GPi which inhibits thalamus

Question 55

what is the function of the indirect pathway

Answer 55

suppresses competing/inappropriate action to the movement initiated by the direct pathway

Question 56

what is hypokinesia and what is it a sign of?

Answer 56

slowness difficulty making voluntary movements increased muscle tone (rigidity) tremors of hand and jaw

Question 57

what is the pathology of parkinsons disease?

Answer 57

degeneration of neurones in the substantia nigra and their dopaminergic (excitatory) inputs to the striatum

Question 58

what is the effect of dopamine in the basal ganglia pathway?

Answer 58

can enhance cortical inputs through the direct pathway and suppress inputs through the indirect pathway?

Question 59

what is the effect of depletion of dopamine?

Answer 59

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

Question 60

what is huntingtons disease caused by?

Answer 60

profound loss of caudate, putamen and globus pallidus - therefore loss of the ongoing inhibitory effects of the basal ganglia

Question 61

what percentage of CNS neurones does the cerebellum contain?

Answer 61

50 percent

Question 62

what do lesions of the cerebellum produce?

Answer 62

uncoordinated, inaccurate movements

Question 63

what parts of movement does the cerebellum instruct?

Answer 63

direction timing force

Question 64

how is the cerebellum linked back to the cortex?

Answer 64

ventrolateral thalamus

Question 65

how does the motor loop for voluntary movement undergo refinement?

Answer 65

via involvement of a feedback loop through the pons, cerebellum, thalamus and then back to the cortex