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Flashcards in motor control 1 Deck (65):
1

what are the 3 levels of motor control hierarchy?

high
middle
low

2

what are the structures associated with high motor control?

association neocortex
basal ganglia

3

what are the structures associated with middle motor control?

motor cortex
cerebellum

4

what are the structures associated with low motor control?

brainstem
spinal cord

5

what do the lateral pathways of the spinal cord control?

voluntary movements of distal muscles - under direct cortical control

6

what do ventromedial pathways control?

posture and locomotion - under brain stem control

7

where does the corticospinal tract decussate?

medulla/spinal cord junction

8

how do CST axons control muscles?

they synapse on ventral horn motor neurones and interneurons

9

where does 2/3ds of the CST originate?

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

10

where does the rubrospinal tract originate?

red nucleus of the midbrain

11

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

fine movements of the arms and hands lost.
unable to move shoulders, elbows, wrist and fingers independently

12

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

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

13

what does the vestibulospinal tract do?

stabilizes head and neck

14

what does the tetospinal tract do?

ensures eyes remain stable as body moves

15

where do the pontine and medullary reticulospinal tracts originate?

brainstem

16

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

balance
body position
vision

17

what is the function of the pontine and medullary reticulospinal tracts?

reflexly maintain balance and body position
innervate trunk and antigravity muscles in limbs

18

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

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

19

where do the medial tracts of white matter originate?

brainstem

20

where do the lateral tracts of white matter develop?

cortex

21

where in the brain is the primary motor cortex?

precentral gyrus

22

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

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

23

what is the function of the supplementary motor area?

innervates distal motor units directly

24

what is the function of the premotor area?

connects reticulospinal neurones innervating proximal motor units

25

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

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

26

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

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

27

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

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

28

what are the decision making neurones in command centres?

neurones in the premotor area

29

when are neurones in area 6 fired?

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

30

how is the direction of movement decided?

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

31

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

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

32

what must happen before movements to change body position start?

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

33

what does cortical damage cause?

immediate flaccidity of contralateral muscle

34

what causes initial hypotonia?

spinal circuits being derived of cortical input

35

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

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

36

what does the babinski sign indicate?

incomplete upper control of spinal circuits

37

what results in spasticity?

removal of cortical suppressive influences

38

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

ventral lateral nucleus in dorsal thalamus

39

what is the basal ganglia motor loop?

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

40

what are the major components of basal ganglia?

corpus striatum

41

what is the input zone of the basal ganglia?

caudate
putamen

42

where does the corpus striatum receive input from?

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

43

where are medium spiny neurones located?

putamen and caudate

44

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

excitatory cortical inputs

45

what kind of inputs do medium spiny neurones integrate?

somatosensory
premotor
motor cortical

46

where do the axons of medium spiny neurones project to?

globus pallidus
substantia nigra
pars reticula

47

when do the neurones of the putamen fire?

before limb/trunk movements

48

when do the neurones of the caudate fire?

before eye movements

49

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

excitation

50

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

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

51

what do globus pallidus neurones do at rest?

inhibit the VL signal

52

what is the effect of inhibiting the globus pallidus?

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

53

how does the indirect basal ganglia loop work?

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

54

what effect does exciting the subthalamic nuclei have

excites GPi which inhibits thalamus

55

what is the function of the indirect pathway

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

56

what is hypokinesia and what is it a sign of?

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

57

what is the pathology of parkinsons disease?

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

58

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

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

59

what is the effect of depletion of dopamine?

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

60

what is huntingtons disease caused by?

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

61

what percentage of CNS neurones does the cerebellum contain?

50 percent

62

what do lesions of the cerebellum produce?

uncoordinated, inaccurate movements

63

what parts of movement does the cerebellum instruct?

direction
timing
force

64

how is the cerebellum linked back to the cortex?

ventrolateral thalamus

65

how does the motor loop for voluntary movement undergo refinement?

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